Mini training- Scenario Driven Design
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The document discusses scenario-driven design, emphasizing the importance of client needs and usage scenarios in API design. It critiques traditional RESTful approaches for exposing raw data and stresses the necessity of considering business logic within APIs. By leveraging specific client scenarios, the goal is to enhance usability, performance, and maintainability while reducing redundancy.
Mini training- Scenario Driven Design
- 1. MAXIME LEMAITRE โ 18/6/2015 Scenario Driven Design โฆ Yet another Blabla Driven Design โฆ
- 2. Agenda โข Inspirations โข The dashboard problem โข Introducing Scenario Driven design โข Examples โ VOD โ Twitter โ Office for Ipad โ โBetclicโ โข Conclusion
- 3. Inspirations Scenario Driven API Design Or: how to make more usable APIs By Ivo Jansch (APIDays, Paris)
- 4. โฆ a long time ago โฆ Our page is so slow to load can you fix the performance problem ?
- 5. โข The design โ /orders โ /orders/:id โ /orders/:id/details โ /products โ /products/:id โ โฆ 5 The basic design โA Home page showing the userโs open orders, the order status, one product for each order plus the thumb, and a list of the last 5 sent ordersโ โฆ What about performance ? 26 API Calls !! โBut our API is so RESTfull !โ Whatโs the problem ?
- 6. Whatโs the problem ? What is a REST resource ? Is you raw data model ? Where is the Business logic ? Where it should be ? What if you need to release a new client ? (WebApp, Mobile, โฆ)
- 7. Whatโs the problemยฒ ? โข This is not a REST problem โ REST is a great way to expose data โข Butโฆ โ REST is not an excuse to expose your raw data model โ REST is not an excuse to stop thinking about business logic โSmart Data & dumb code works a lot better than the other way aroundโ The Cathedral & The Bazaar, Eric S. Raymond ๏ Smart APIs, dump clients Note : Batch requests could help, but business logic is still on client side...
- 8. Introducing โScenario Driven API Designโ
- 9. Introducing Scenario Driven Design 1. Client analysis โ Identify client needs โ Usage scenarios 2. Service design โ Optimal ways to service the client scenarios 3. Data modelling โ Create data model to support the scenarioโs โ Low level and high level concepts 4. Interface design โ REST/HAL etc. interface โ Versioning, etc. Reminders : โข Data Driven Design ๏ from Data to generic clients โข Client Driven Design ๏ from Specific clients to data
- 11. Scenario Driven Design Approach โข Identify all relevant scenarios โ Order a movie โ Watch a movie โ See list of my movies โ Promote content on the home screen โ See whatโs available โ Like/unlike movies Interactions are platform-specific, Scenarios usually arenโt.
- 12. Promote content on the home page โข All clients should present, on their home screen, after login: โ The userโs most recently rented movies โ User specific recommendations โ Movie top 20 โ Featured movies
- 13. Scenario Driven Design (1) โHomeโ screen (4) /promoslots/home (2) Promote content to the home screen (3) Movies, collections, banners,
- 14. Interface Design โข Exemples โ /recommendations โข or /users/@me/recommendations โ /promoslots/:screen โ /users/@me/movies โ /users/@me/movies/liked โ /movies โข Consider scenarioโs at the highest level โ Business Logic entirely API side โ Important: find balance between generic and specific
- 15. Framework Design Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries by Krzysztof Cwalina & Brad Abrams โ Frameworks often contain a very large set of APIs. This enables advanced scenarios that require power and expressiveness. However, most development revolves around a small set of common scenarios that use a relatively small subset of the full framework. To optimize the overall productivity of the developers using a framework, it is crucial to invest heavily in the design of APIs that are used in the most common scenarios.โ
- 16. Do & Donโt http://blogs.msdn.com/b/kcwalina/archive/2005/05/05/scenariodrivendesign.aspx โข Do make sure that the API design specification is the central part of the design of any feature that includes a publicly accessible API. โข Do define top usage scenarios for each major feature area. โข Do ensure that the scenarios correspond to appropriate abstraction level. They should roughly correspond to the end user use cases. โข Do design APIs by first writing code samples for the main scenarios and then defining the object model to support the code samples. โข Do not rely solely on standard design methodologies (for example UML) when designing the public APIs layer of a framework. โข Do not start API design with object model diagrams. โข Do organize usability studies to test APIs in main scenarios.
- 17. Examples
- 18. The example of Twitter API โข The Twitter API exposes many methods for tweets, favorites, retweets, followers, search, โฆ โข What is the most common feature of twitter ? => Timelines โข The home timeline is central to how most users interact with the Twitter service. Do no try to reinvent the wheel Dumb clients, Smart APIs
- 19. Office for Ipad โdesigned for iPadโ as opposed to โported to iPad โข Several key mobile scenarios โ Packing up for the ride home โ Starting from scratch โ Last minute scramble โ Buttoning things up โ Collaborating with coworkers โ Taking notes โข โbringing over hundreds of Office commands, toolbars, and dialogs to the iPad would be, simply put, a mistake.โ
- 20. Conclusion - Better Usability - Better Performance - Better maintainability - Less duplicates
- 21. Questions
- 22. References โข http://blogs.msdn.com/b/kcwalina/archive/2005/05/05/scenariodrivendesign.asp x โข https://speakerdeck.com/ijansch/scenario-driven-api-design-apidays-paris โข https://speakerdeck.com/ijansch/scenario-driven-api-design โข https://github.com/dotnet/corefx/wiki/Framework-Design-Guidelines-Digest โข http://www.slideshare.net/clintedmonson/advanced-oop-laws-principles-idioms- presentation?qid=63cb2104-5ac7-48e9-b3eb- aebf85cf7459&v=qf1&b=&from_search=1 โข http://www.streetinsider.com/Insiders+Blog/Microsoft+%28MSFT%29+Shows+Ho w+Office+for+iPad+was+Designed/9519656.html