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The document discusses requirements analysis in software engineering, outlining its role in specifying software characteristics and interfaces, and emphasizing the importance of building models for user scenarios and domain analysis. It details various modeling techniques, including use-cases, data modeling, and class-based modeling, which help represent and organize the interactions, data, and behaviors required in software development. Through illustrating analysis classes, operations, and relationships, the document serves as a guide for software engineers in conducting thorough requirements analysis.
![Domain Analysis
Software domain analysis is the identification,
analysis, and specification of common
requirements from a specific application domain,
typically for reuse on multiple projects within that
application domain . . .
[Object-oriented domain analysis is] the
identification, analysis, and specification of
common, reusable capabilities within a specific
application domain, in terms of common objects,
classes, subassemblies, and frameworks . . .
Donald Firesmith](https://image.slidesharecdn.com/07-01-200701133453/85/Bridge-4-320.jpg)
![Scenario-Based Modeling
“[Use-cases] are simply an aid to defining what
exists outside the system (actors) and what
should be performed by the system (use-
cases).” Ivar Jacobson
(1) What should we write about?
(2) How much should we write about it?
(3) How detailed should we make our
description?
(4) How should we organize the description?](https://image.slidesharecdn.com/07-01-200701133453/85/Bridge-7-320.jpg)
Bridge
- 1. Software Engineering II By: Muhammad Usman email:[email protected]
- 2. Requirements Analysis Requirements analysis specifies software’s operational characteristics indicates software's interface with other system elements establishes constraints that software must meet Requirements analysis allows the software engineer (called an analyst or modeler in this role) to: elaborate on basic requirements established during earlier requirement engineering tasks build models that depict user scenarios, functional activities, problem classes and their relationships, system and class behavior, and the flow of data as it is transformed.
- 4. Domain Analysis Software domain analysis is the identification, analysis, and specification of common requirements from a specific application domain, typically for reuse on multiple projects within that application domain . . . [Object-oriented domain analysis is] the identification, analysis, and specification of common, reusable capabilities within a specific application domain, in terms of common objects, classes, subassemblies, and frameworks . . . Donald Firesmith
- 5. Domain Analysis Define the domain to be investigated. Collect a representative sample of applications in the domain. Analyze each application in the sample. Develop an analysis model for the objects.
- 6. Elements of Requirements Analysis
- 7. Scenario-Based Modeling “[Use-cases] are simply an aid to defining what exists outside the system (actors) and what should be performed by the system (use- cases).” Ivar Jacobson (1) What should we write about? (2) How much should we write about it? (3) How detailed should we make our description? (4) How should we organize the description?
- 8. Use-Cases a scenario that describes a “thread of usage” for a system actors represent roles people or devices play as the system functions users can play a number of different roles for a given scenario
- 9. Developing a Use-Case What are the main tasks or functions that are performed by the actor? What system information will the actor acquire, produce or change? Will the actor have to inform the system about changes in the external environment? What information does the actor desire from the system? Does the actor wish to be informed about unexpected changes?
- 10. Use-Case Diagram homeowner Access camera surveillance via the Internet ConfigureSafeHome system parameters Set alarm cameras SafeHome
- 11. Activity Diagram enter password and user ID select major function valid passwords/ ID prompt for reentry invalid passwords/ ID input t ries rem ain no input t r ies r em ain select surveillance ot her f unct ions may also be select ed t hum bnail views select a specif ic cam er a select camera icon prompt for another view select specific camera - thumbnails exit t his f unct ion see anot her cam era view camera output in labelled window Supplements the use case by providing a graphical representation of the flow of interaction within a specific scenario
- 12. Swimlane Diagrams Allows the modeler to represent the flow of activities described by the use-case and at the same time indicate which actor (if there are multiple actors involved in a specific use-case) or analysis class has responsibility for the action described by an activity rectangle enter password and user ID select major function valid p asswo rd s/ ID prompt for reentry in valid p asswo r d s/ ID in p u t t ries r emain n o in p u t t ries r emain select surveillance o t h er f u n ct io n s may also b e select ed t h u mb n ail views select a sp ecif ic camera select camera icon generate video output select specific camera - thumbnails exit t h is f u n ct io n see an o t h er camera h o m e o w n e r c a m e ra i n t e rf a c e prompt for another view view camera output in labelled window
- 13. Data Modeling examines data objects independently of processing focuses attention on the data domain creates a model at the customer’s level of abstraction indicates how data objects relate to one another
- 14. What is a Data Object? a representation of almost any composite information that must be understood by software. composite information—something that has a number of different properties or attributes can be an external entity (e.g., anything that produces or consumes information), a thing (e.g., a report or a display), an occurrence (e.g., a telephone call) or event (e.g., an alarm), a role (e.g., salesperson), an organizational unit (e.g., accounting department), a place (e.g., a warehouse), or a structure (e.g., a file). The description of the data object incorporates the data object and all of its attributes. A data object encapsulates data only—there is no reference within a data object to operations that act on the data.
- 15. Data Objects and Attributes A data object contains a set of attributes that act as an aspect, quality, characteristic, or descriptor of the object object: automobile attributes: make model body type price options code
- 16. What is a Relationship? Data objects are connected to one another in different ways. A connection is established between person and car because the two objects are related. A person owns a car A person is insured to drive a car The relationships owns and insured to drive define the relevant connections between person and car. Several instances of a relationship can exist Objects can be related in many different ways
- 17. ERD Notation (0, m) (1, 1) object objectrelationship 1 One common form: (0, m) (1, 1) object 1 object 2 relationship Another common form: attribute
- 18. Building an ERD Level 1—model all data objects (entities) and their “connections” to one another Level 2—model all entities and relationships Level 3—model all entities, relationships, and the attributes that provide further depth
- 19. The ERD: An Example (1,1) (1,m) placesCustomer request for service generates (1,n) (1,1) work order work tasks materials consists of lists (1,1) (1,w) (1,1) (1,i) selected from standard task table (1,w) (1,1)
- 20. Class-Based Modeling Class-based modeling represents: objects that the system will manipulate operations (also called methods or services) that will be applied to the objects to effect the manipulation relationships (some hierarchical) between the objects collaborations that occur between the classes that are defined.
- 21. Identifying Analysis Classes Classes are determined by underlining each noun or noun phrase and entering it into a simple table. Synonyms should be noted. If the class (noun) is required to implement a solution, then it is part of the solution space; otherwise, if a class is necessary only to describe a solution, it is part of the problem space.
- 22. Manifestations of Analysis Classes External entities (e.g., other systems, devices, people) that produce or consume information Things (e.g, reports, displays, letters, signals) that are part of the information domain for the problem Occurrences or events (e.g., a property transfer or the completion of a series of robot movements) that occur within the context of system operation Roles (e.g., manager, engineer, salesperson) played by people who interact with the system Organizational units (e.g., division, group, team) that are relevant to an application Places (e.g., manufacturing floor or loading dock) that establish the context of the problem and the overall function Structures (e.g., sensors, four-wheeled vehicles, or computers) that define a class of objects or related classes of objects
- 23. Potential Classes Retained information. The potential class will be useful during analysis only if information about it must be remembered so that the system can function. Needed services. The potential class must have a set of identifiable operations that can change the value of its attributes in some way. Multiple attributes. During requirement analysis, the focus should be on "major" information; a class with a single attribute may, in fact, be useful during design, but is probably better represented as an attribute of another class during the analysis activity. Common attributes. A set of attributes can be defined for the potential class and these attributes apply to all instances of the class. Common operations. A set of operations can be defined for the potential class and these operations apply to all instances of the class. Essential requirements. External entities that appear in the problem space and produce or consume information essential to the
- 24. Defining Attributes Attributes describe a class that has been selected for inclusion in the analysis model. For Playing Statistics software: name, position, batting average, fielding percentage, years played, and games played might be relevant For Pension Fund software: average salary, credit toward full vesting, pension plan options chosen, mailing address, and the like.
- 25. Defining Operations Do a grammatical parse of a processing narrative and look at the verbs Operations can be divided into four broad categories: (1) operations that manipulate data in some way (e.g., adding, deleting, reformatting, selecting) (2) operations that perform a computation (3) operations that inquire about the state of an object, and (4) operations that monitor an object for the occurrence of a controlling event.
- 26. CRC Models Class-responsibility-collaborator (CRC) modeling provides a simple means for identifying and organizing the classes that are relevant to system or product requirements. A CRC model is really a collection of standard index cards that represent classes. The cards are divided into three sections. Along the top of the card you write the name of the class. In the body of the card you list the class responsibilities on the left and the collaborators on the right.
- 27. CRC Modeling Class: Description: Responsibility: Collaborator: Class: Description: Responsibility: Collaborator: Class: Description: Responsibility: Collaborator: Class:FloorPlan Description: Responsibility: Collaborator: incorporates w alls, doors and w indow s show s position of video cameras defines floor plan name/type manages floor plan positioning scales floor plan for display scales floor plan for display Wall Camera
- 28. Class Types Entity classes, also called model or business classes, are extracted directly from the statement of the problem (e.g., FloorPlan and Sensor). Boundary classes are used to create the interface (e.g., interactive screen or printed reports) that the user sees and interacts with as the software is used. Controller classes manage a “unit of work” from start to finish. That is, controller classes can be designed to manage complex communication between sets of objects; validation of data communicated between objects or between the user and the application.
- 29. Responsibilities System intelligence should be distributed across classes to best address the needs of the problem Each responsibility should be stated as generally as possible Information and the behavior related to it should reside within the same class Information about one thing should be localized with a single class, not distributed across multiple classes. Responsibilities should be shared among related classes, when appropriate.
- 30. Collaborations Classes fulfill their responsibilities in one of two ways: A class can use its own operations to manipulate its own attributes, thereby fulfilling a particular responsibility, or a class can collaborate with other classes. Collaborations identify relationships between classes Collaborations are identified by determining whether a class can fulfill each responsibility itself three different generic relationships between classes the is-part-of relationship the has-knowledge-of relationship the depends-upon relationship
- 31. Composite Aggregate Class Player PlayerHead PlayerArms PlayerLegsPlayerBody
- 32. Associations and Dependencies Two analysis classes are often related to one another in some fashion In UML these relationships are called associations Associations can be refined by indicating multiplicity (the term cardinality is used in data modeling In many instances, a client-server relationship exists between two analysis classes. In such cases, a client-class depends on the server- class in some way and a dependency relationship is established
- 33. Multiplicity WallSegment Window Door Wall is used to buildis used to build is used to build1..* 1 1 1 0..* 0..*