Api for dummies

by Claus T. Jensen
APIs
IBM Limited Edition

APIs For Dummies®
, IBM Limited Edition
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Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
About This Book......................................................................... 1
Icons Used in This Book............................................................. 2
Beyond the Book......................................................................... 3
Chapter 1: The Anatomy of an API. . . . . . . . . . . . . . . . . . . 5
Looking at What an API Is Not................................................... 5
The Product Nature of APIs....................................................... 6
From APIs to API Economy........................................................ 6
Understanding What Developers Want.................................... 7
Chapter 2: Managing APIs — And Not. . . . . . . . . . . . . . 11
Seeing What It Means to Manage an API................................ 11
API business owner........................................................ 12
IT operations................................................................... 13
API designer.................................................................... 13
The Need for API Governance................................................. 14
API provider decisions................................................... 14
API consumer decisions................................................ 15
Making the Case for Unmanaged APIs.................................... 15
Chapter 3: Discovering the Nature of Good APIs . . . . . 17
Comparing APIs with Race Cars.............................................. 17
Making the Case for Opportunistic APIs................................ 18
Thinking of APIs and Services................................................. 19
APIs versus services....................................................... 20
APIs teaming with services............................................ 22
Recognizing Good API Design................................................. 22
Chapter 4: API Entry Points. . . . . . . . . . . . . . . . . . . . . . . . 25
Monetize Your Data.................................................................. 26
Freedom to Innovate................................................................ 27
Mobile In Ten Minutes.............................................................. 30
Living in a Hybrid World.......................................................... 32
Program Your World................................................................ 35

APIs For Dummies, IBM Limited Editioniv
Chapter 5: API and Integration Middleware . . . . . . . . . 39
API Middleware Isn’t “just another ESB”............................... 40
The (Repeatable) Topology of Integration............................ 42
API and Service-Economy Reference Model.......................... 44
Chapter 6: Ten Things to Know about APIs . . . . . . . . . . 47
The Omnichannel Experience Drives the Need for APIs..... 47
APIs Are Business Products.................................................... 48
Business Design Is an End-to-End Endeavor......................... 48
You Can Gain Insight from API Instrumentation................... 49
Not All APIs Are REST............................................................... 49
Every API Needs a Business Owner........................................ 49
APIs Do Need to Be Versioned................................................ 50
APIs Are Easy to Control with Policies.................................. 50
APIs Have a Dark Side............................................................... 50

Introduction
APIs are a hot topic, energetically debated by business-
people, IT managers, and developers alike. Most of the
excitement in the public space is about open public APIs. To
some degree, not having a public API today is like not having
a website in the late 1990s. Yet for many enterprises, public
APIs are really the least of their business concerns. More
important concerns include building omnichannel solutions,
innovating faster than the competition, becoming a mobile
enterprise, or operating in a hybrid cloud environment.
APIs are fundamental enablers for all these initiatives and
more, which is why so many different types of stakeholders
are interested in them. But what is an API, really; why is it
different from an old-school application programming inter-
face; and why should you care? In principle, the acronym API
stands for Application Programming Interfaces, but the notion
of what API means has evolved significantly. APIs today are
quite different from the application programming interfaces of
old. Read this book and see what that change entails.
About This Book
Modern business ecosystems need to rethink their approach to
innovation and integration. This book is your guide to applying
the power of APIs to business challenges ranging from changing
business models to embracing a world of devices and sensors.
Experiencing the power of APIs involves much more than simply
data monetization. Whether you’re an API provider or an API
consumer, you need to make smart business and IT decisions.
This book first defines the basic nature of modern APIs and then
leads you through several necessary decisions, ranging from
which APIs to provide or consume to how you can build an
effective API technology platform.

APIs For Dummies, IBM Limited Edition2
A handful of important mottos are also touched on multiple
times throughout the book. These include the following:
✓ Think of an API as a product. It represents something
you have chosen to share with a particular audience
under defined terms and conditions.
✓ Try early, learn fast, scale easily. An experimenting
approach to APIs is effective for most use cases, and
many APIs will be opportunistic in nature.
✓ Always use APIs as the boundary of your domain. That
gives you control and visibility of traffic going in and out.
✓ API platforms are specialized for the task. You want the
creation, operation, and sharing of APIs to be dead easy
and 100 percent secure.
✓ Monetizing public APIs is not the only entry point.
Many enterprises use APIs for collaboration and innova-
tion across their IT and business ecosystems.
Icons Used in This Book
Like all For Dummies books, this one has a few icons in the
margins. Here’s what they mean.
The Tip icon points out helpful information.
Anything marked with the Remember icon is good to keep in
mind.
If you’re not interested in the nitty-gritty technical details, you
can skip anything that has a Technical Stuff icon.
Take care when you see the Warning icon, which alerts you to
things that could harm your business.

3Introduction
Beyond the Book
This short publication can’t offer every detail about a topic.
So for more information outside the realm of this book, check
out the following links:
✓ developer.ibm.com/api/blog: IBM’s API blog
✓ www.redbooks.ibm.com/Redbooks.nsf/
RedbookAbstracts/sg248188.html?Open: In-depth
asset for integration middleware
✓ ibm.com/soa: Download the SOA Design Principles For
Dummies eBook

Chapter 1
TheAnatomyofanAPI
In This Chapter
▶ Knowing what an API isn’t
▶ Seeing how developers and consumers want to use APIs
▶ Categorizing APIs
▶ Making APIs part of the business model
Modern APIs are flexible ways of projecting your capa-
bilities to an audience outside of your own team. When
done right, APIs enable enterprises to innovate faster and
reach new audiences. That is the value of APIs, but what is
their basic nature, and what key questions should you ask
when embarking on an API journey? This chapter attempts to
answer those questions.
Looking at What an API Is Not
Sometimes, the best way to explain something is to explain
what it’s not. With that in mind, here are a few things that APIs
aren’t:
✓ A piece of software: Software isn’t an API (but it may
render itself as an API to ease consumption of its
capabilities).
✓ A user interface: A user interface isn’t an API (but it may
be built on top of one).
✓ A server: A server isn’t an API (but it may host one or
more APIs that expose the data and functions provided
by the server).

The Product Nature of APIs
Think of an API as a product. You carefully craft it so it’s
attractive to the intended consumer — so that it sells. It nei-
ther matters whether that consumer really pays for the API
nor if she’s outside your enterprise or part of a different team
inside it. You want her to use your API, because she creates
value for both of you when she does.
The product nature of APIs is fundamental to their power. It
also makes them very different from old-school application
programming interfaces. An old-school application program-
ming interface represents a piece of software that you have
built and deployed. A modern API represents a package of
capabilities that’s attractive to an audience independent of
any specific piece of software running in your back end. So
although modern APIs do include a defined programmatic
interface, they’re deliberately designed from the perspective
of the intended consumer.
Because an API is a product, before you develop one, you
should ask yourself these key questions:
✓ Who are the intended consumers?
✓ How are you going to reach these consumers?
✓ Under what terms and conditions can consumers use
this API?
From APIs to API Economy
The API economy emerges when APIs become part of the busi-
ness model. Public and partner APIs have been strategic enablers
for several business models, such as Twitter’s and Amazon’s.
The Twitter APIs, for example, easily have ten times more traf-
fic than the Twitter website does. The company’s business
model deliberately focuses on tweet mediation, letting anyone
who wants to do so provide the end-user experience.

Chapter 1: The Anatomy of an API 7
From the get-go, Amazon chose to be not just an Internet
retailer, but also a ubiquitous merchant portal. Amazon’s mer-
chant platform is deliberately built on APIs that allow easy
onboarding of new merchants.
APIs as business network enablers aren’t new. Banks have
built payment infrastructures and clearinghouses based on
well-defined APIs for decades. Modern APIs, however, are built
explicitly for an open ecosystem (internal or external), not
for closed private networks. Furthermore, the consumption
models for APIs are standardized with a focus on ease of con-
sumption rather than ease of creation (see “Understanding
What Developers Want” later in this chapter).
Some people use the term business APIs for all modern APIs.
The term is certainly fitting in the sense that APIs, as prod-
ucts, should be an integral part of your business strategy.
Just be aware that launching a public or partner API isn’t the
only way to make APIs part of your business model. There are
many use cases for internally consumed APIs, perhaps the
most common such use case being the need to provide a dif-
ferentiating omnichannel customer experience.
Whether your business was “born on the web” or has been
around for 100 years, you’re living in the age of cloud, analyt-
ics, mobile, and social computing where omnichannel has
become table stakes. To differentiate yourself from your com-
petitors, you have to give customers an immediately engaging
experience. To deliver that experience, you need freedom to
experiment and innovate. Seize the opportunity and try early,
learn fast, and scale easily.
Understanding What
Developers Want
Developers want to use APIs for innovation and experimenta-
tion. To them, reuse is about speeding time to delivery, shar-
ing is about expediency, and encapsulation is about having
little to learn. They’re not as interested in how APIs were cre-
ated (and at what cost) as they are in how easy the APIs are to
consume.

Easy consumption doesn’t refer only to what the API looks
like. To the developer who is API savvy, easy consumption
also means that an API must be easy to find and easy to reg-
ister to use, and it must be clear how much the API can be
trusted in mission-critical solutions.
Ideally, an API ecosystem should be community-centric. An
effective API community shows developers the exact APIs
available to them for their current tasks. Self-service registra-
tion and preapprovals are already in place for the APIs that
are visible to the community. The community’s social features
allow people to like or dislike a particular API, and consumer-
centric analytics show the expected operational behavior
of any API of interest. These capabilities historically aren’t
part of IT governance, but they’re core features of good API
management solutions. Good API management solutions also
add value for API providers, making it easier to create APIs
and improving control of their runtime behavior (explained in
more detail in Chapter 2).
Four categories of APIs
When you’re starting on an API jour-
ney, deciding which APIs to build first
can be daunting. A good API should
make a difference to the business.
In some cases, industry specific use
cases can drive the creation of APIs.
But to truly understand what makes a
good API for a particular enterprise,
you need to understand the nature of
its unique business situation.
In this sidebar you find an approach
that IBM has found useful in prac-
tice. A good way to start is to ask
yourself, “Which business situations
would I like to improve, and how can
I do that?” When you answer this
question, you’ll likely end up choos-
ing your first APIs from one of the
following four categories:
✓ Detection APIs: Detection APIs
help you identify opportunities
to engage customers, employ-
ees, partners, and devices. They
include mechanisms such as
mobile location detection, sensor
monitoring, predictive analytics,
and human observation.
✓ Enrichment APIs: Enrichment
APIs improve understanding of
the situation with historical data
from customer relationship man-
agement(CRM)systems,account
records, demographical analysis,
health records, and the like.
✓ Perception APIs: Perception
APIs provide dynamic context for
the current situation and enable

Chapter 1: The Anatomy of an API 9
you to understand what may
be on the minds of the people
you want to engage. Examples
are social APIs (people sharing
future plans or current inter-
ests) and sensor analytics (for
the overall system state, such
as global resource consumption
or traffic congestion). After all,
someone who’s going on a trip
to the Caribbean next Monday
is probably interested in differ-
ent things from someone who’s
staying in winter-cold Chicago.
✓ Action APIs: Action APIs enable
you to take action in near real
time. Examples of action-type
interfaces include push notifi-
cations, instrumented devices,
and human-task management
systems.

Chapter 2
ManagingAPIs — AndNot
In This Chapter
▶ Reviewing API management roles and tasks
▶ Establishing API governance
▶ Seeing when to use unmanaged APIs
Part and parcel of many API conversations is the notion
of API management. Even though APIs aren’t pieces
of software in the traditional sense (see Chapter 1), they’re
important elements of both business and IT operating envi-
ronments, so they need to be managed appropriately. In this
chapter, you find out how.
Seeing What It Means
to Manage an API
To an API consumer, a great developer portal is everything. To
an API provider, managing the API externalization and sharing
processes is only the tip of the iceberg (see Figure 2-1). Under
the waterline are the business and IT concerns that make APIs
practical to create, deploy, and operate. These concerns include
data mapping, security, rate throttling, monitoring, and version
management.
A managed API not only has a well-defined interface and
a defined target audience but also is under appropriately
enforced business and IT controls. Different groups have
specific parts to play in API management, as you see in this
section.

Figure 2-1: Managing APIs requires more than API design and
externalization.
For maximum effectiveness, all three roles addressed in
this chapter — business owner, IT operations, and API
designer — need their own user-experience designs. Their
concerns are sufficiently different that one role’s tools are
inefficient for another role.
API business owner
The API business owner decides the following:
✓ The plans (terms and conditions) under which the API
can be consumed
✓ The communities that the API will be shared with
✓ Whether the API is succeeding in its objectives (if not,
the business model needs adjustment)
All this can be done without changing the API definition or
implementation in any way. For more about the business
owner’s role, see “The Need for API Governance” later in this
chapter.
These materials are © 2015 John Wiley Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited.

Chapter 2: Managing APIs — And Not 13
IT operations
IT operations must ensure certain operational characteristics, all
of which can also be done without changing the API definition or
implementation in any way. These characteristics are as follows:
✓ The runtime that hosts the API can be operated securely
and robustly.
✓ The API is properly authenticated, and authorization is in
place for anyone who uses it.
✓ API traffic is optimized and prioritized according to busi-
ness needs.
There’s a fundamental difference between what the API owner
sells in terms of API plan access and what the underlying IT
infrastructure can provide. Having spare capacity to support
the full potential of traffic corresponding to API plans sold can
be very costly.
To prevent prohibitive runtime costs, make sure that your API
runtime is highly scalable (so that actual loads matter less)
or apply traffic throttling when current load surpasses avail-
able capacity to smooth out traffic spikes. These capabilities
should be available in your selected API runtime.
For more about IT operations’ role, see “The Need for API
Governance” later in this chapter.
API designer
The person that holds the API designer role physically creates
and deploys the API. She needs to do the following:
✓ Define the API interface
✓ Discover back-end endpoints that may provide the data
or function required to implement the API
✓ Configure the mapping between the API interface and the
back-end data or function sources
The API designer must be able to perform these tasks without
doing a lot of coding. As soon as creating an API becomes
code-intensive rather than a matter of dynamic configuration,
the rate of innovation inevitably slows, even for the most agile

development teams. The distinction between configuring an
API and developing the back-end data or function embody-
ing that API is fundamental to API thinking. As pointed out in
Chapter 1, modern APIs aren’t a piece of software; modern
APIs are a flexible way of projecting capabilities to audiences
outside your own team.
The Need for API Governance
A common myth in API circles is that governance bogs every-
thing down. But governance is about making good decisions —
making sure that the right people make the right decisions
at the right time and for the right reasons, based on the right
information. So if an API is important to your organization, you
want to make good decisions about it. As an API provider or an
API consumer, you have several decisions to make about APIs.
This governance is a different kind of governance from the
type that’s routinely applied as part of a software delivery life
cycle; nevertheless, it’s important.
API provider decisions
Deciding who can use the API under which business terms
and conditions is the job of the API business owner. This
business operational decision applies to all APIs, whether
they’re the APIs that your mobile development team uses to
build mobile apps, the APIs that you use to integrate systems
across various lines of business, or the APIs used by external
consumers, so you probably want to make different decisions
for each of these audiences in terms of what APIs they may
use under which conditions.
IT operations also needs to make appropriate API provider
decisions — typically, in the form of security and traffic
policies — to protect the infrastructure from misuse or
overload.
The governance regime needs to be very lightweight, and the
decisions must be operational in nature as opposed to the
typical life-cycle decisions made during a software delivery
life cycle. If the right decisions can’t be made and enforced
easily, the open and dynamic nature of APIs is compromised

Chapter 2: Managing APIs — And Not 15
(remember, good API implementations are configurations, not
code). Business and IT decisions are both part of good API
management discipline and should be supported by the chosen
API platform. (For more about API middleware, see Chapter 5.)
API consumer decisions
API consumers also need to make good decisions. In particular,
they need to decide which APIs they’re willing to use for what
purposes and then ask the following questions about each API:
✓ What is the payment model for using the API and is that
acceptable for your purpose?
✓ Will you need a corporate proxy in front of the API to
handle licenses, payment, and the like, or will every
developer register independently?
✓ Is the API secure and reliable for mission-critical purposes?
Any historical records about how the API has behaved
over time may add to consumer confidence in using it.
When the APIs being consumed are your own, these decisions
are pretty straightforward, being mainly about overall busi-
ness design. When the APIs are third-party APIs, the decisions
become more complicated. Ultimately, the end-user experi-
ence and responsibility for maintaining business integrity
can’t be delegated. You need someone in your own organiza-
tion to be responsible for the end-user experience and to
make the right decisions about which APIs it’s appropriate to
consume as part of your delivery model.
Making the Case for
Unmanaged APIs
Everyone knows that modern APIs must be powered by an
API management solution, right? Not so fast. Not all APIs are
necessarily managed. Throughout this chapter, I’ve defined
good API management, but what does it mean for an API to be
unmanaged?
Here are the key differences between managed and unman-
aged APIs:

✓ An unmanaged API may have an intended target audience,
but this target audience is rarely precisely defined, let
alone enforced. If a user has network access to the API,
generally, he can invoke it.
✓ An unmanaged API doesn’t have independently enforced
business and IT controls. Any control is provided via logic
in the API implementation, usually in the form of code.
In other words, unmanaged APIs still have a well-defined inter-
face, but there’s no way to enforce controls on their runtime
behavior or even on who may use them. So why would you
want any API to be unmanaged?
If an API is a direct part of your business model, you probably
don’t want it to be unmanaged. Having said that, I give you a
few examples of situations in which having unmanaged APIs is
appropriate or even unavoidable:
✓ A device or sensor has a defined API as part of its physi-
cal reality, such as a home thermostat that can be pro-
grammed remotely or a Fitbit (a wearable device that
monitors physical activity) that synchronizes data with a
computer via a defined interface.
✓ An existing software system — perhaps a standard
system such as SAP or a mainframe system with a native
REST interface — exposes a micro API.
✓ The API sits inside your own domain, and all you really
need is connectivity to access it.
Unmanaged APIs can be important resources in many ecosys-
tems, making key functions and data available in a uniform
fashion. The uniform consumption model is the reason why
you still want to think of these interfaces as APIs. Often, you
even want to catalog all the unmanaged APIs that are available
to you, to make them easy to find and as simple as possible to
use in a particular programming model.
Turning everything into an API, as seen from the consumer, is
the easiest and most effective way of innovating and collabo-
rating in a hybrid environment. This means that thinking APIs
isn’t just about API management and managed APIs. Thinking
APIs should be part of a bigger integration strategy for turning
your enterprise into an innovation engine.

Chapter 3
DiscoveringtheNature
of GoodAPIs
In This Chapter
▶ Seeing why APIs are like race cars
▶ Using opportunistic APIs
▶ Combining APIs with Service Oriented Architecture
▶ Understanding good API design
Rapid innovation is enabled by good design — which, for
any given API, includes its interface and technical charac-
teristics. More important, good design is about which APIs to
provide and when. If all you are trying to do is provide a handful
of stable public APIs, perhaps the question of which ones is not
so complicated. But what if you are trying to do that, as well as
create a partner ecosystem, as well as use APIs to fuel internal
innovation? There are many different kinds of APIs and uses for
them, so in this chapter, you learn what makes a good API.
Comparing APIs with Race Cars
You could make an apt analogy between APIs and how
Formula 1 racing teams build and evolve race cars (see
Figure 3-1). In Formula 1 racing, every single car ever raced is
a prototype. No team takes the same car to two consecutive
races. A race car is built from rapidly replaceable components
with well-defined interfaces, and the car itself is instrumented
with built-in controls and analytics.
Although parts of the car may remain stable throughout the
season, some component is always optimized based on les-
sons learned in the previous race.

Figure 3-1: Race cars and APIs should be built to the same design
principles.
Modern enterprises are in many ways like Formula 1 teams,
always trying to optimize the business model and always look-
ing for the right balance between change and stability. APIs
are one way in which experimentation can be harnessed for
enterprise advantage. “Try early, learn fast, and scale easily”
is a good principle to apply to the world of APIs.
Making the Case for
Opportunistic APIs
Should APIs always be designed to be reusable? Reusability
implies stability over a relatively long period, and stability is
appropriate if an API is to be used for partner integration or
exposed externally as part of your business model. But if the
API is created simply to improve collaboration between, say, a
mobile development team and the team that maintains a back-
end system of record, reusability may be neither desirable nor
appropriate.
An API needs to be attractive to use, and for a developer, it
must be faster and more expedient to use that API than to
code a different solution. If the needs of a mobile developer
change rapidly, the APIs must change just as fast to keep up.

Chapter 3: Discovering the Nature of Good APIs 19
This situation makes the case for opportunistic APIs — rapidly
created, rapidly changing APIs defined to meet a specific con-
sumer need. For more information about the developer point
of view, see Chapter 1.
Nothing in the concept of an API requires it to necessarily
be reusable or stable over time. The importance of reusabil-
ity and stability depends solely on your business purpose
for having the API. If that business purpose involves rapid
change, opportunistic APIs are appropriate.
Providing opportunistic APIs requires that creating and
maintaining APIs is both easy and cheap. Otherwise the cost
of opportunistic change becomes impractically high. So API
management software focuses on this challenge.
Good API management solutions create APIs via configuration
rather than coding, and the task of creating or changing an
API usually takes only minutes. The nature of an easily man-
aged API is simply that it is both defined and controlled by
configuration. Regardless of the cost of creation and mainte-
nance, there’s significant value in managing even opportunis-
tic APIs properly (see Chapter 2).
Managing opportunistic APIs provides the following benefits:
✓ Definition and enforcement of business and IT controls
✓ Global insight into how an API performs from a business
perspective
✓ IT operational flexibility for moving and dynamically scal-
ing API workloads
These benefits are important aspects of try early, learn fast,
and scale easily and are critical for optimizing change in a
world of opportunities and innovation.
Thinking of APIs and Services
Service-oriented architecture (SOA) has been mainstream for
about a decade; modern APIs are more recent. Both approaches
to integration have their proponents and address business and
IT concerns alike. What’s the real difference between these
approaches, and do you need to choose between them?

APIs versus services
The core concept of SOA is the notion of a service. The Open
Group, for example, defines a service as “a logical representa-
tion of a repeatable activity that has a specified outcome.”
Services are self-contained and opaque to their consumers,
and they have well-defined interaction contracts. From a tech-
nical perspective, these characteristics also apply to any well-
designed API, so technically, an API is also a service.
In that case, are APIs just another name for services? Well,
there’s one important difference between services and
APIs, however, and that’s the goal behind their design (see
Figure 3-2). APIs are always designed to be attractive to the
intended consumer, and they change as the needs of the con-
sumer change. Services, in contrast, are generally designed
with global cost and stability as the most important concerns.
In the car analogy, the API is the race car designed for looks
and consumption, but the service is the regular car designed
for cost and mass production.
Figure 3-2: APIs and services address different concerns.
Chapter 1 describes the product nature of APIs and states
that they should be aimed at the needs of a particular group
of consumers. To a consumer, using an API is about speed,
expediency, and having little to learn. Those design criteria

are the fundamental differences between APIs and the classi-
cal notion of services, at least different from the perspective
of the service provider:
✓ To a service provider, reuse is about effort involved in
API delivery. To API consumers, reuse is about speed of
delivery of their software, no matter the cost to provide
the APIs consumed as part of that sofware.
✓ To a service provider, sharing is about effectiveness. To
an API consumer, sharing is about expediency (if it isn’t
expedient, the API will not be used).
✓ To a service provider, encapsulation is about having little
to change. To an API consumer, encapsulation is about
having little to learn (if the interface is complex, the API
will not be used).
How often have you not seen an SOA initiative slowed down
by conflicts between service providers and service consum-
ers on what constitutes a good service interface? On the one
side, a mobile developer just wants it to be simple for her par-
ticular app. On the other side, the back-end team wants every-
one to use the same standardized service and data model.
Instead of forcing a resolution of this conflict, is there a way to
meet both needs without incurring prohibitive cost?
A historical analogy exists in the evolution of databases. The
first generations of databases were focused exclusively on the
internals, the tables, schemas, and data procedures. Quickly
though, it became obvious that there was a need to expose
controlled subsets of data in a particular form, fitted to a par-
ticular group of data consumers — and the notion of a data
view emerged as a core capability in most modern databases,
a lightweight proxy on top of the data domain represented by
the internals of the database.
APIs are controlled (proxy) views of the data and capabilities
of a domain, optimized for the needs of API consumers. As
long as it’s dirt cheap to create and maintain proxy APIs, you
can use them to render a domain in multiple forms, optimized
for each group of API consumers. (After all, you probably
want to give external partners a different view of your capa-
bilities from the view your internal developers have.)

APIs teaming with services
SOA emerged as a means of shielding service consumers
from changes in the back end. But who protects the service
providers from the churn of changing needs in omnichannel
front-end solutions? Applying APIs and services together lets
you create an eye of calm in a hurricane of change. Services
are the means by which providers codify the base capabilities
of their domains. APIs are the way in which those capabilities
(services) are repackaged, productized, and shared in an easy-
to-use form. APIs and services are complementary rather
than contradictory, and applied together, they dramatically
increase the overall effectiveness of enterprise innovation.
Recognizing Good API Design
No doubt the technical design of APIs is important, but it also
varies widely with the technology choices made for the design
and implementation of any particular API. For instance, what
constitutes a well-designed REST interface is very different
from what constitutes a well-designed SOAP interface. Entire
books have been written about interface design, providing
a level of detail way beyond what this small book can offer.
Suffice it to say that interface design of APIs is generally well
understood, as witnessed by these examples:
✓ REST interfaces are resource-based. The most important
aspect of the interface design is the URI structure that
allows a consumer to navigate the object graph embod-
ied by the API.
✓ SOAP interfaces are method-based. The most important
aspects of the interface design are the set of supported
methods and the data structures of each method.
✓ MQTT interfaces are event-based. The most important
aspects of the interface design are the set of events
(emitted or received) and the associated event messages.
Not all APIs are REST. Generally, REST interfaces are excellent
for human consumption, and they are the current preference
of mobile developers. But REST interfaces tend to be chatty,
and though they’re extendable, they don’t carry strongly

typed complex data structures. SOAP interfaces are great for
system-to-system integration, and IT operations teams prefer
them due to their less chatty nature and more precise data
structures. MQTT interfaces are preferred for communicating
with the Internet of Things, in which bandwidth and battery
life are key concerns, and guaranteed delivery may be the dif-
ference between preventing accidents and inadvertently let-
ting them happen.
There is more to understanding API
value than the so-called API value chain
Much of the hype about APIs is cen-
tered on the API value chain illus-
trated in this sidebar figure — the
way that APIs extend a business
model into an open ecosystem.
Unfortunately most of the examples
discussed in the industry at large are
exclusively around public APIs, and
this is by far not the only use case
for APIs. Even more unfortunately,
the generic value chain picture is
uninteresting from the perspective
of which APIs to provide and why.
The reason being that it says nothing
about the different types of business
objectives that may have led you
to consider APIs in the first place.
Chapter 4 addresses that concep-
tual gap by defining the typical API
entry points with associated deci-
sion criteria.

Chapter 4
APIEntryPoints
In This Chapter
▶ Monetizing your data
▶ Taking advantage of innovation
▶ Speeding the transition to mobile
▶ Going hybrid
▶ Programming everything
What does it really mean, to “think APIs”? Some people
simply point to the so-called API value chain (see
Chapter 3), but is that all there is to it? Is that what the excite-
ment is all about? I believe that there is more to understand-
ing APIs. As discussed in Chapter 2, decisions have to be
made regarding the balance between enterprise and oppor
tunistic APIs. There are decisions around the terms and condi-
tions under which APIs can be shared, and there are decisions
regarding how to map required APIs to existing assets during
API implementation. All of these decisions and more depend
on the desired business outcome.
The key part of the phrase “think APIs” is the first word:
Think. Think about what you’re trying to achieve business
wise, which audience to engage, what kinds of APIs are
required to engage the audience, and how to curate your data
and application assets (as services) to support those APIs
that you need to provide. In the process, don’t forget to think
about what APIs you’re going to consume yourself and from
whom. Thinking APIs is not just about being an API provider;
many organizations consume several times the number of
APIs that they provide. These concerns are the core elements
of an effective API strategy.

This chapter defines five API entry points that, in my experi-
ence, are representative for the business and IT agendas driv-
ing API thinking. An enterprise may have multiple agendas
at the same time, but each agenda leads to different decision
criteria for API adoption. You can read the chapter from
beginning to end or you can jump to the entry point that best
matches your business needs.
Monetize Your Data
Monetizing your data is based on externalizing insights or
functions in a form that entices third parties to use those
insights or functions. Monetization can come in many forms.
The most obvious example is when the third party is paying
to use your API. In other cases, you may actually be the one
paying the API consumer in return for a broader business
reach and a stronger ecosystem. Or you may be onboarding
partners via APIs without any direct payment involved at all.
The key business objectives for monetization are pivoting
your business, changing your value chain, and increasing your
reach and influence.
Success with this entry point likely requires careful planning.
Although you can and should do some experimentation, “oppor-
tunistic style,” the final product must be a set of stable enterprise
APIs that a third party can depend on for a prolonged period.
Thinking about APIs in the context of monetizing your data,
here is some guidance:
✓ Goal: The desired outcome is monetary or based on a
nonmonetary value such as increasing your influence.
✓ Audience: The audience is inevitably a third party.
Typical cases are partners and external developers (not
developers in your own organization or developers hired
by your own organization). Treating a different line of
business within your enterprise as a partner or third
party isn’t uncommon, particularly when the different
lines of business are treated as economically independ
ent entities.
✓ APIs to provide: The APIs required to engage the audi-
ence must provide the value you want to sell. This choice

Chapter 4: API Entry Points 27
requires careful thought — not just in terms of the root
value provided, but also in terms of the form that makes
consumption attractive.
✓ API terms and conditions: Don’t forget to include in your
considerations the terms and conditions under which
API consumption may happen, such as freemium, pay as
you go, or prepaid contract.
✓ API implementation: The way you curate the data
and function to implement the APIs comes down to
quality and reliability. Some people say that cost of
implementation is the most important factor, but imple-
mentation cost won’t make or break a data-monetizing
strategy. What decides long-term viability is whether
the intended API consumers experience both value and
trustworthiness.
✓ Consuming somebody else’s APIs: In some cases, you
also need to consider which APIs to consume. Although
you generate value primarily by providing APIs for others
to consume, implementing those APIs may involve creat-
ing higher-level composites of existing APIs, most often
by blending those existing APIs with something that’s
uniquely yours.
The data-monetizing entry point may be the one you’ve heard
the most about, but it’s not the most common one. Currently,
a significant majority of API initiatives are for internal use
cases, and this may remain the case even when public API
exchanges become fully mature.
Freedom to Innovate
Freedom to innovate is the most important imperative
for many businesses today. Try early, learn fast, scale
easily — key characteristics of a dynamic, engaging enter-
prise. The focus of this API entry point is to chase business
opportunities aggressively and to make innovation a learning
process through the following model:
✓ Everything is a prototype until it’s proved in practice.
✓ Discovering that something didn’t work isn’t failure; it’s
just learning.
✓ Standing still guarantees decline.

As discussed in Chapter 3, the role of APIs is to provide the
calm center in a storm of change. This role has two aspects:
✓ Delivering quickly what the experimenting API consumer
needs and removing it when it’s no longer needed
✓ Protecting the provider from churn (see Chapter 3 for a
refresher on why defining and deploying new API “views”
on existing assets should be easy and cheap)
The Freedom to Innovate entry point is perhaps not as glamor-
ous as Monetize your Data (see the preceding section), but it’s
by far the API use case that IBM sees the most in major enter-
prises. The ability to compose new innovative capabilities,
internal and/or external, without breaking the bank in terms of
cost, is something that everyone is struggling with. To acceler-
ate innovation, a blend of careful planning and opportunistic
reaction is required.
Thinking about APIs in the context of freedom to innovate,
✓ Goal: The desired outcome is to quickly discover what
works and what differentiates in the market and then to
scale successes.
Even when you believe that you know what the market
needs, a learning attitude can deliver a healthy reality
check. It’s easy to get symptom and cause mixed up
when you’re dealing with complex market dynamics.
✓ Audience: The audience is primarily internal developers,
in-house or outsourced. Sometimes, external agencies are
hired to be part of an innovation effort. In these cases,
more formal agreements about which APIs to provide and
when are required, but even then, it’s best to maintain
some opportunistic behavior to maintain learning speed.
Contract negotiations are anathema to fast innovation.
ence are a blend of predefined enterprise APIs and
opportunistic APIs (see Chapter 3) derived from the
needs of an innovative app. Mixing in some enterprise
APIs to expose core data in an easily accessible fash-
ion can kick-start not only development, but also idea
generation.

Keep the predefined APIs small and simple. Exposing the
full data structure of a customer back-end system proba-
bly wouldn’t be easy for an innovative channel developer
to consume.
✓ API terms and conditions: The terms and conditions under
which API consumption happen remain important — not in
terms of payment, but in terms of protecting the security
and stability of back-end systems. After all, innovation is
unpredictable.
✓ API implementation: The way you curate the data and
functions required to implement the APIs is different for
preplanned enterprise APIs and opportunistic, demand-
driven APIs:
• For preplanned APIs, you must make careful deci-
sions about which data segments to expose at an
organizational level. Also, your implementation
(typically proxy’ing enterprise services) needs to
take ultimate runtime cost into account. Preplanned
APIs will be used in unpredictable ways, so runtime
cost must not be a preventing factor for such use.
• For opportunistic APIs, the most important consid-
erations are development speed and development
cost. If you have to do a hack to get the API out the
door today rather than next week, do so as long
as you have a viable plan for cleaning up the API
implementation if and when that API becomes a
success.
Many opportunistic APIs may not live very long. If
it turns out that you need something different, just
scratch the opportunistic API and start over in the
next iteration of the learning process.
✓ Consuming somebody else’s APIs: Considering which
third-party APIs to consume is important for this entry
point. As a simple example, building social mobile apps
is difficult without accessing APIs from well-known public
social services such as Twitter, Facebook, and LinkedIn.
These third-party APIs should be part of the API catalog
that you provide your internal developers; they shouldn’t
have to go to some external site to find things themselves.
You may even want to curate the third-party APIs into your
own, simpler version, as some of the public APIs are quite
complex in their native forms.

Innovation is never easy, but it can be aided in various ways.
Proper use of APIs can make the corporate back end an integral
part of your innovation engine rather than a millstone around
your neck. Enterprises with a long history have the advantage
of having more assets to expose as APIs. But even for startups,
an API-driven approach to implementing innovative solutions
provides more flexibility in terms of sourcing data and function.
The use of APIs frees channel developers to focus on the user
experience rather than integration. The use of APIs also pro-
motes an omnichannel experience, as the data and functions
behind the API by definition are remote and can be accessed
from any channel or application across the enterprise.
Mobile In Ten Minutes
This API entry point is strongly related to the freedom-to-
innovate entry point (see the preceding section) and can be
considered to be an extreme variant. The difference is that
for this entry point, everything is about opportunistically
supporting what your mobile development team needs here
and now.
Enterprises today need to create many small, self-contained
apps, rather than traditional comprehensive portals. I strongly
believe that mobile consumers prefer to orchestrate their own
omnichannel experiences instead of having someone else pre-
define the process. I see it in my own behavior where I rarely
spend more than a couple of minutes in a given mobile app
before moving on to something else.
The mobile in ten minutes entry point involves improving col-
laboration between back-end owners and mobile development
teams. Those mobile development teams can be internal or
external, but in all cases they need to leverage existing data
and functions easily to provide an engaging experience. Being
able to see stock prices is useful, for example, but being able
to do something with them in the context of your own invest-
ment portfolio is the true differentiator.
The focus of this entry point is controlled simplicity. Hide
complexity, simplify what the mobile developer sees and con-
sumes, and at the same time provide appropriate business
and IT operational control. Also, the process has to be fast in
order to not slow down mobile innovation.

Just for the fun of it, some IBM developers tested whether
it was possible to take a piece of data on a mainframe and
put it on a mobile device, using an API approach, in 10 to 15
minutes. It was indeed possible! There wasn’t any pretty API
design, but it proved that the complexity of integration logic
can largely be taken out of the equation by appropriate use of
API and integration technology.
Mobile in ten minutes is all about opportunistic innovation.
Thinking about APIs in that context, here is some guidance:
✓ Goal: The desired outcome is immediate support for the
needs of your mobile development teams. The mobile
team is responsible for figuring out what data the end
user experience requires, and the back-end owner builds
the APIs that deliver exactly that data. Mapping to exist-
ing data and functions (services) is part of the API imple-
mentation, not the responsibility of the mobile developer.
✓ Audience: The audience for the APIs is your mobile
development team, period.
ence are almost exclusively opportunistic. You may be
lucky enough to be able to apply existing APIs to a new
mobile app, but you want to avoid creating too many
cross-app dependencies on particular API contracts.
✓ API terms and conditions: The terms and conditions
under which API consumption happen are about protect-
ing the security and stability of back-end systems. The
same is true for Freedom to Innovate (see the preceding
section).
✓ API implementation: As the APIs produced are very
opportunistic and rarely live long, the most important
considerations are development speed and development
cost. If you have to do a hack to get the API out the door
today rather than next week, do so as long as you have a
viable plan for cleaning up the API implementation if and
when that API becomes a success.
✓ Consuming somebody else’s APIs: Engaging mobile
applications typically need a social element, so it’s
crucial to consider which public social APIs (such as
Twitter, Facebook, and LinkedIn) to consume and how to
control that consumption. You may want to curate the
third-party social APIs into your own, simpler version

(refer to “Freedom to Innovate” earlier in this chapter).
At minimum, you must consider the dark side of APIs
(see Chapter 6) and try to minimize the impact on your
business reputation if any stability or ethical issues arise
from the public APIs that you end up using.
The opportunistic approach of this API entry point may sound
unmanageable, due to the number of APIs involved and their
inevitably limited reuse — and indeed with the technology
available even three to four years ago, it would have been
practically unfeasible for many large enterprises. Not so
today! API management software changes the equation with
its ability to easily delineate a lightweight consumer-centric
API from the portfolio of software-based enterprise data and
services. If it’s dead easy to create a new API, and if it’s simple
to manage and share large numbers of APIs with various com-
munities, reuse and architectural rigor on the API interfaces
are much less of a concern. Instead, the main concern is what
will make the API consumer successful.
Living in a Hybrid World
No book about APIs would be complete without discussing
how APIs relate to cloud. The fourth API entry point focuses
on using APIs as the uniform consumption model in a hybrid
ecosystem of on-premise systems and private and public
cloud environments. The business mantra is “freedom of
choice” — freedom to choose how to source any function or
data and freedom to deploy solutions to any desired form
factor.
An API-centric approach to integration is driven by the
following:
✓ A disconnected enterprise isn’t competitive, so cloud
equals hybrid solutions across cloud parts and on-premise
parts, and integration needs to be managed at scale.
✓ Cloud is about capability (business and IT), not loca-
tion, so any ubiquitous consumption model needs to be
location-independent.
✓ In a “system of systems” world, there’s no traditional
network perimeter to enforce, so interactions need to be
controlled at the application level.

If to a consumer everything is a (remote-able) API, then the
consumer doesn’t need to know anything about where and how
that API is hosted. Syndicated API catalogs can and should pro-
vide visibility across domain and provider boundaries. In this
API entry point, one of the most important aids for a developer
is the catalog of APIs that are readily available for consumption.
Don’t show every single API out there (there are too many);
show only the ones that are relevant to the developer in ques-
tion. That developer shouldn’t have to care about how and why
the API is procured; she should focus solely on what she can do
with the API after it has been made available to her.
In a hybrid world, the domain structure is inevitably complex.
Public marketplaces, private API catalogs, partner portals,
and more are part of the API fabric. Consequently, a well-
defined community structure is more important than ever,
with direct correlation between community design decisions
and API design decisions.
Figure 4-1 illustrates how a developer can use APIs to securely
access any part of a hybrid environment. At development
time, the API marketplace provides information about the
APIs that are available to the community of that developer.
At runtime, the cloud gateways secure the communication
between the API consumer environment and any API end-
point, independently of location.
Figure 4-1: Using APIs as the lingua franca for a hybrid environment.

Thinking about APIs in the context of living in a hybrid world,
✓ Goal: The desired outcome is to empower both develop-
ers and IT operations. Careful controls need to be placed
on the APIs made available, and any communication on
an open network needs to be secure and appropriately
managed.
The most-often-cited reason for not adopting a hybrid
cloud approach is security concerns. The second-most-
often-cited reason is fear of losing operational control.
✓ Audience: The audience can be any mix of internal and
external developers who are part of the hybrid ecosys-
tem, so designing appropriate community structures is
very important. Making decisions at the single-person
level is highly impractical; you need a structure that
allows you to make and enforce API sharing decisions at
the community level, treating all developers in a particu-
lar community in the same fashion.
✓ APIs to provide: The APIs you need to engage the audi-
ence depend on the audience community structure. For
external audiences, you probably need a good set of
predefined enterprise APIs; for internal audiences, you
need some opportunistic APIs to support rapid creation
of innovative apps. No hard-and-fast rule applies to all
hybrid cases; each hybrid case tends to be different.
✓ API terms and conditions: The terms and conditions
under which API consumption happens can be com-
plicated in a hybrid world — business-wise as well as
IT-wise. This holds true whether the APIs are managed
or unmanaged (see Chapter 2), yet the implementation
mechanisms usually are very different for the two:
• For managed APIs, you apply business and IT poli-
cies in the normal fashion on the API platform —
this is one of the advantages of using APIs as the
uniform consumption model. Just make sure that
your API platform is community-aware so that you
can make decisions at the appropriate community
level.
• For unmanaged APIs, the only vehicle for enforcing
business terms and conditions is community visibil-
ity, along with any formal agreements that you estab-
lish through side channels. Where unmanaged APIs

are concerned, IT operations has no built-in way
of enforcing API-level security and traffic controls;
unmanaged APIs must instead be invoked through
secure tunnels established at the network level.
✓ API implementation: The way that you curate the
data and functions to implement the APIs differs for
preplanned enterprise APIs and opportunistic, demand-
driven APIs. As described in “Freedom to Innovate” ear-
lier in this chapter, the key differences are robustness
and runtime cost versus time and development cost.
third-party APIs to consume is harder for this entry
point than for any of the other entry points because
over time, the number and variety of available APIs is
dramatically greater.
The best advice is to start simple on API consumption.
Pick a small number of important APIs that you want to
consume: social APIs, analytical APIs, mobile back-end
APIs, or something else, depending on your most immedi-
ate business need. You also have the option of curating
third-party APIs into your own simpler or more con-
trolled version, so take that option into account in your
decision-making.
Hybrid environments are intrinsically complex. Using APIs as
the lingua franca can make that complexity much more man-
ageable from a developer perspective. From an IT operational
perspective, complexity may become manageable due to the
evolution in hybrid cloud platforms.
Program Your World
The final API entry point focuses on the world of devices and
machinery. It’s based on two beliefs: The consumer-driven
mobile revolution is about more than just phones, and manu-
facturing and logistics will drive the intelligent corporate
Internet of Things.
Healthcare, utilities, cities, manufacturing — practically
everywhere you turn, you see the need for a more intelli-
gent approach to blending people, software, and machines.
Granted, the idea of programming everything into a single
intelligent experience is still emerging, but signs of progress

toward that goal are seen every day in such examples as
smart cars, interactive retail experiences, and ecofriendly
buildings.
One important difference separates this entry point from the
others: You generally can’t change a device after it exists in
its physical form. That fact in turn means that the device APIs
remain what they are. Therefore, the focus shifts to providing
an enriched experience with optimized execution, as follows:
✓ Extend software into the physical realm.
✓ Control any component, software, or device through pro-
grammable APIs.
✓ Use device-driven feedback and insight to optimize
the behavior of the entire system, not just a single
component.
✓ Where appropriate, monetize your high-level control
capabilities as your own set of APIs (refer to “Monetize
Your Data” earlier in this chapter).
The programming-the-world entry point usually is much more
about API consumption than it is about providing new APIs.
Thinking about APIs in the context of programming the world
around you, here is some guidance:
✓ Goal: The desired outcome is a completely programma-
ble environment. Look for a programmable physical infra-
structure, and build your own software to be controllable
through APIs as well.
✓ Audience: The audience is mostly internal. Your own
developers are the ones who’ll be building smart systems
on top of device and software APIs. If you’re a producer of
devices yourself, you do need to make sure that your own
devices have APIs intended for consumption by others as
required by your business model.
✓ APIs to provide: The APIs you need to engage the audi-
ence are largely defined by whatever interfaces are
designed into your physical devices and machinery. You
don’t have a whole lot of choice, as the majority of the
APIs you’ll be using are predefined.
✓ API terms and conditions: If you have network access
to a device, you can most likely communicate with it

because its APIs are by definition unmanaged. Terms and
conditions are not as important for this entry point as
they are for the others. Much more important is having a
good library of available device APIs.
In some cases you do want to control access to the
device-level APIs and can do so by adding in front of the
device APIs a layer of managed proxy APIs with built-in
security controls.
✓ API Implementation: For device APIs, the methods used
to curate the data and functions to implement the APIs
aren’t your concern (unless, of course, you are a pro-
ducer of physical devices).
third-party APIs to consume is very important for this
API entry point. Having the right agreements in place
with third-party suppliers of devices and machinery
is critical. If you don’t have updated API documenta-
tion, you simply can’t communicate effectively with the
device.
As the world gets smarter and more instrumented, the need
for Program your world capabilities will continue to rise.
Because this environment is quite different from a classical
software-only environment, getting an early start may be
necessary. Embarking on this journey requires developers
and businesspeople alike to get experience in what it means
to seamlessly program interactions among devices, software,
and people.

Chapter 5
APIandIntegration
Middleware
In This Chapter
▶ Understanding API middleware
▶ Choosing a domain topology
As I discuss in earlier chapters, there are key distinctions
between managed and unmanaged APIs. A managed API
has appropriately enforced business and IT controls, which in
turn begs the question of where and how those controls are
enforced at runtime.
Enforcing the controls in code generally is a bad idea. For one
thing, it’s notoriously unreliable, depending on the code qual-
ity of every single API implementation. Furthermore, an organ
ization really needs to be able to change the controls without
having to change and redeploy the API itself. In other words,
the controls should be policy-driven, with independently
managed policies defining the (business and IT) operational
intent and the API runtime enforcing that intent. Examples of
common policies are the level of security required and the
amount of traffic allowed.
A piece of middleware that hosts APIs and enforces API poli-
cies is commonly called an API gateway. Don’t forget that API
platforms aren’t just about the runtime; they need develop-
ment time capabilities as well.

API Middleware Isn’t
“just another ESB”
Have you ever heard someone say, “I already have an enter-
prise service bus (ESB), so I’m all set for APIs”? The implica-
tion is that API middleware is “just another ESB.” In fact, there
are significant differences:
✓ Ideally, APIs are defined by configuration rather than
coding. Defining the API by configuration preserves
the lightweight nature of the API proxy and supports
fast turnaround for new and changed APIs. By contrast,
general-purpose ESB tools are flow- or code-centric, and
service implementations are part of the enterprise soft-
ware delivery life cycle. Even with continuous delivery,
a code-centric approach is difficult to maintain while
attempting to meet the need for rapidly changing oppor-
tunistic APIs (see Chapter 2).
✓ API runtimes need to be lightning-fast, completely secure,
robust, and highly scalable. Ideally, the API gateway has
routerlike network characteristics, so adding an API proxy
as part of an end-to-end interaction never creates prob-
lems with response time or latency. The fastest and most
scalable API gateways are based on domain-specific, light-
weight configuration languages with stateless execution.
Although general-purpose ESB runtimes also need to be
fast, robust, and scalable, the execution engines must be
able to support full-scale composition and some amount
of statefulness. Consequently, general-purpose ESB run-
times can’t be as highly optimized for throughput as API
runtimes.
✓ APIs have policy-driven business and IT controls ranging
from authentication to traffic controls and the business
terms and conditions under which the API may be con-
sumed (the API plan). Although some comprehensive
ESBs include traffic-management policies, few have the
security-policy capabilities and certification of a full-
scale API gateway, and none has the separate business
controls embodied in an API plan. Furthermore, the soft-
ware nature of ESB executables typically provides less
room for operations to control runtime objects indepen-
dently after deployment.

Chapter 5: API and Integration Middleware 41
✓ APIs must be made available to app developers in a self-
service fashion. Any kind of post-deployment approval
process slows the adoption rate and ultimately, at scale,
generates significant organizational costs.
The preferred sharing mechanism — one that has proved
to be highly effective — is publishing APIs to developer
portal environments. In particular for internal API use,
sharing is preferably managed on a community basis,
making sure that given developers see only the APIs that
their community is supposed to use.
General-purpose ESBs include none of these features, and
even service management solutions (whether embedded
or separate) are aimed more at service development time
controls and operational controls than at optimizing the
developer sharing process.
✓ Finally, API owners need business statistics about who
uses their APIs and how much. These statistics measure
success against the business objectives for the portfo-
lio of APIs rather than focusing on IT concerns such as
the operational dashboards typically included in ESB
platforms.
Some people may argue that you need only one bus, which
can be repurposed to support classical integration needs,
service-oriented architecture (SOA), and also API manage-
ment. Yet without providing dedicated experiences for the API
developer, API owner, and API consumer, you risk engineering
the middleware for the lowest common denominator. Not to
mention that the classical integration developers also need
their separate optimized experience. Further, if you need only
API management or general-purpose integration capabilities,
why pay for both?
Modern enterprises need API management as well as enter-
prise integration, but as two separate platforms aimed at
different target audiences. Do remember, though, that if you
are already doing SOA, you have a good set of assets that you
can quickly discover, assemble into (proxy) APIs, and expose
through an API management platform.

The (Repeatable) Topology
of Integration
An API gateway controls traffic across the boundary between
API consumer and API implementation; it also enforces the
terms and conditions for API consumption defined by the
API owner. Historically, we’ve tended to think of different
types of gateways — be they web, security, messaging, or
API gateways — as being distinct “boxes” in a deployment
topology. In a hybrid world of devices, people, and software,
however, the perception of distinct gateway boxes is rapidly
evaporating. As the scale and variety of interaction grow
by orders of magnitude, it’s operationally advantageous to
have a unified gateway strategy with a single command-and-
control center for any traffic that crosses internal or external
boundaries.
As a good practice, traffic across a domain boundary should
always happen through an API. This approach to integration
creates a desirable level of visibility and control. Furthermore,
it provides maximum flexibility in terms of balancing enter-
prise and opportunistic implementations in a way that’s com-
pletely invisible to the API consumer.
The choice of a coarse-grained or fine-grained domain topol-
ogy is up to the individual enterprise. Typical domain bound-
aries are driven by the following:
✓ Organization (such as mobile developer versus back-end
team)
✓ Ownership (such as line-of-business boundaries)
✓ Security (such as demilitarized zone [DMZ] versus inter-
nal network)
✓ Quality of service (such as mainframe versus distributed)
✓ Ecosystem (such as public or partner)
It’s important that this suggested integration topology model
be both repeatable and composeable. For each domain within
an ecosystem, good practice dictates the same topology
structure, with cross-domain interactions at runtime always
going through a (API) gateway as illustrated by Figure 5-1. In
the figure each separate domain has the same structure of

concentric circles with different types of integration capabili-
ties. The standard integration topology for each domain can
be composed to a system-of-systems topology across multiple
domains simply by repeating the pattern. In other words, the
domain structure can be defined by the needs of the enterprise,
yet the API sharing and consumption mechanisms remain the
same. This structure crisply addresses the system-of-systems
nature of hybrid integration environments and is a good fit for
any API entry point defined in Chapter 4.
Figure 5-1: The topology of integration is a repeatable pattern.
Some people would argue that latency or response time is
an issue in a pattern that always goes through an API for
cross-domain interaction. Good API gateways make latency
and response time nonissues, as outlined in “API Middleware
Isn’t Just another ESB” earlier in this chapter. As an analogy,
how often do you ponder the number of routers between a
browser and a web server? Hardly ever. You just assume that
the router infrastructure is fast enough and scalable enough
that the number of routers isn’t an issue. Granted, the actual
network distance between two points can and will add some
amount of latency, but this latency is due to network distance
rather than the number of network routers involved. Good API
gateways are like routers in this respect; adding one of these
gateways on the path from API consumer to API provider
makes no noticeable difference.

Use general-purpose ESBs in the integration bus role, curat-
ing data and function into well-formed services. Then define
(proxy) APIs to control the productization of those services
in the ecosystem beyond your own domain. Finally, run all
API traffic through a highly scalable, robust, and secure API
gateway. That way, each part of the end-to-end integration
platform is used in the area of its main strength (refer to
Figure 5-1).
If you’re interested in further details on the nonoverlap-
ping capabilities of an end-to-end integration topology, see
the IBM Redbook Integration Throughout and Beyond the
Enterprise at www.redbooks.ibm.com/Redbooks.nsf/
RedbookAbstracts/sg248188.html?Open.
API and Service-Economy
Reference Model
Back in the 2000s, IBM defined an SOA reference model that
outlined the middleware capabilities required to create,
deploy, and manage services effectively. In the API economy,
those capabilities are still important, as services are the basis
on which APIs can be defined, but they’re no longer sufficient.
Embracing an open ecosystem, delivering APIs as part of a
business product, and carefully promoting and managing your
cross domain business persona require more than classical
integration middleware.
The reference model for this extended middleware platform
is defined in Figure 5-2. It is a practical guideline for the set of
middleware capabilities to seek across your integration and
API platforms.
The integration-centric elements of the original IBM SOA refer-
ence model are rendered in compressed form as the bottom
layer of the API and service-economy reference model. In addi-
tion, the new reference model has capabilities for defining and
managing APIs, for developer portals and marketplaces, as
well as capabilities that accelerate the consumption of APIs.

It’s important not to make decisions about the parts of the refer-
ence model in isolation. Instead, use an integrated middleware
strategy to turn assets into business advantages.
Figure 5-2: The API and service economy reference model.

Chapter 6
TenThingstoKnow
about APIs
In This Chapter
▶ Seeing that APIs are products
▶ Recognizing that design never stops
▶ Understanding that every API needs an owner
Part of an API journey is the mental mindset that lets an
organization think about APIs in an effective fashion.
This chapter contains some of the things that I have learned
on my own journey through the world of APIs.
The Omnichannel Experience
Drives the Need for APIs
The basic concept of APIs isn’t new. The difference now is that
modern users (consumer and enterprise) expect an omnichan-
nel experience that’s both social and personal. To be truly
personal, the experience must be self-orchestrated, at least to
some degree. No longer can an enterprise define a “one size
fits everything” channel process.
Self-orchestration inevitably points in the direction of micro
apps, which in turn lead to the need for purpose-built APIs. An
omnichannel experience implies an ecosystem that includes
people, software, and devices, which again leads to the need
for purpose-built APIs.

APIs Are Business Products
Thinking of APIs as business products makes it easier to
tell the difference between an API-centric approach and a
classical software-delivery approach. For products, you have
several key questions to ask:
✓ Who is the audience?
✓ What do they want to buy?
✓ What are the terms and conditions under which I’m will-
ing to sell?
The terms buy and sell are used deliberately even though
the economic models behind APIs vary widely. Whether the
“price” is cash or influence, whether the model is consumer-
paid or provider-paid, the product nature of the API persists.
Business Design Is an
End-to-End Endeavor
APIs are no longer just IT concerns. APIs should be part of
your end-to-end business design.
Consider a traveler who shares her experiences on social
channels. One day, she tweets about a really bad experience
with Airline A. Ten minutes later, she receives an email from
the airline that says: “We’re sorry about your bad experi-
ence. Here is what we can do for you.” The next week, she
has a great travel experience with Airline B, and as usual, she
tweets about it. Five minutes later, that airline retweets her
tweet with this added text: “Happy you had a good experi-
ence. See you next time.”
Both these airlines considered in advance how to weave
social channels, through the use of APIs, into their overall
business operating models.

Chapter 6: Ten Things to Know about APIs 49
You Can Gain Insight from
API Instrumentation
Try early, learn fast, scale easily — part of that recipe is the
ability to learn fast, and the best way to learn fast is to tap into
information already flowing through the business operating
system. You can access this information easily via instrumen-
tation of APIs and use of associated business analytics —
capabilities that should be part of a fully functional API middle-
ware platform.
Not All APIs Are REST
A common myth is “SOAP is dead; APIs are always REST.”
Although most modern APIs are currently based on REST/
JSON rather than SOAP, this fact doesn’t mean that there’s no
use for the formalism of SOAP — merely that such formalism
isn’t necessary for human consumption of APIs (the focus of
most current API discussions). There are still plenty of uses
for SOAP in machine-to-machine communication and formal
composition tools. There are good reasons why the industry
has invented more than one binding protocol; good designers
choose the right one for the purpose.
Every API Needs a
Business Owner
Simply put, no business API owner equals no responsibility
and no decision-making power. It’s human nature for people to
resist owning things that they don’t control completely (as in
“Only this part is my responsibility”). Nevertheless, you must
assign a business owner to every single API. That person then
becomes the focal point of decisions about productization
and sharing.

APIs Do Need to Be Versioned
Saying that APIs aren’t versioned is like saying that you don’t
need to change a baby’s diaper. Obviously, disruptive changes
happen, and when they do, you have to handle them. Claiming
that versioning isn’t necessary merely means letting the con-
sumers of an API figure out the versioning themselves.
Because APIs are business products, you should version them
wisely. Reduce version churn by coining a new official version
only when an update isn’t backward-compatible.
APIs Are Easy to Control
with Policies
Policies are the traditional ways that business and IT opera-
tions intentions get codified; therefore, they’re vehicles for
business consistency and integrity. The terms and conditions
under which APIs are consumed and managed should be codi-
fied as policies, which in turn are enforced by API platforms.
It’s important to make sure that policies can be changed
independently of the logic embodying the API itself (such as
interface and data mapping). This supports dynamic change
of operating behavior.
APIs Have a Dark Side
Innovation without business integrity is a fragile value propo-
sition. Whether the breach of integrity is a broken promise,
exposure of sensitive information, or inappropriate behavior,
the result is largely the same. It takes only one bad experience
for someone to lose faith in you.
When you use a third-party API, take care that your own
business’s integrity won’t be negatively affected. The vehicle
you use — formal agreements with penalties, compensation
mechanisms, or judicious evaluation of API robustness and
security — matters less than the fact that you’ve taken proper
precautions. Remember to include ethical concerns in your
consideration.

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