Advance Software Engineering (CEN-5011) Requirements Analysis: Object Modeling Fall 2004 Instructor: Masoud Sadjadi http://www.cs.fiu.edu/~sadjadi/Classes/CEN-5011/

Acknowledgements Dr. Bernd Bruegge Dr. Allen Dutoit Overview: Motivation Overview Concepts Activities Management Summary

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

Motivation Ambiguity: what do you see? Overview: Motivation Overview Concepts Activities Management Summary

Approach From Use Cases to Objects Top Level Use Case A and B Overview: From Use Cases to Objects Motivation Overview Top Level Use Case A and B are called Participating Objects Le v el 1 A B Level 3 Use Cases el 3 Operations el 4 Level 2 Use Cases el 2 Concepts Activities Management Summary

Our Focus Identification of objects Their Behavior Their Relationship Overview: Identification of objects Their Behavior Their Relationship Their Classification Their Organization Motivation Overview Concepts Activities Management Summary

Object vs Class Object (instance): Exactly one thing Overview: Object (instance): Exactly one thing A class describes a group of objects with similar properties Object diagram: A graphic notation for modeling objects, classes and their relationships ("associations"): Class diagram: Template for describing many instances of data. Useful for taxonomies, patters, schemata... Instance diagram: A particular set of objects relating to each other. Useful for discussing scenarios, test cases and examples Motivation Overview Concepts Activities Management Summary

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

system specification: Analysis Overview Overview: Analysis results in a model of the system that aims to be correct, complete, consistent, and unambiguous. Motivation Overview Concepts Activities system specification: Model analysis model: Problem Statement Requirements Analysis Elicitation Management Summary

Req. Elicitation vs. Analsis Overview: Developers focus on structuring and formalizing the elicited requirements. Motivation Overview Concepts Analysis functional model nonfunctional requirements analysis object Requirements elicitation dynamic model Analysis Model Specification System design Object design Activities Management Summary

The Analysis Model Overview: The analysis model is composed of the functional model, the object model, and the dynamic model. Motivation Overview Concepts Activities Management class diagram:View statechart diagram:View sequence diagram:View Summary use case diagram:View object model:Model dynamic model:Model functional model:Model analysis model:Model

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

Analysis Concepts Analysis Object Models and Dynamic Models Overview: Analysis Object Models and Dynamic Models Entity, Boundary, and Control Objects Generalization and Specifications Motivation Overview Concepts Activities Management Summary

Analysis Object and Dynamic Models Overview: The analysis object model focuses on the individual concepts that are manipulated by the system, their properties, and their relationships. depicted by class diagrams. The dynamic model focuses on the behavior of the system. depicted with sequence diagrams and with statecharts. Motivation Overview Concepts Activities Management Summary

Example Overview: Examples and counterexamples of classes in the analysis object model of SatWatch. Motivation Overview Concepts Activities Management Domain concepts Software classes Summary UniversalTime TimeZoneDatabase TimeZone GPSLocator Location UserId

Object Types 1 Entity Objects Boundary Objects Control Objects: Overview: Entity Objects Represent the persistent information tracked by the system (Application domain objects, “Business objects”). Boundary Objects Represent the interaction between the user and the system. Control Objects: Represent the control tasks performed by the system. Motivation Overview Concepts Activities Management Summary

Object Types 2 Overview: Having three types of objects leads to models that are more resilient to change. The interface of a system changes more likely than the control The control of the system change more likely than the application domain Object types originated in Smalltalk: Model, View, Controller (MVC) Motivation Overview Concepts Activities Management Summary

Example Analysis classes for the 2Bwatch example Overview: Analysis classes for the 2Bwatch example Motivation Overview Concepts Activities Management Summary <<entity>> Year <<control>> ChangeDateControl <<boundary>> ButtonBoundary <<entity>> Month <<boundary>> LCDDisplayBoundary <<entity>> Day

Generalization and Specialization Overview: Inheritance enables us to organize concepts. At the top of the hierarchy is a general concept. At the bottom are the most specialized concepts. Generalization is the modeling activity that identifies abstract concepts from lower-level ones. Specialization is the activity that identifies more specific concepts from a high-level one. Generalization-specialization relationship is another name for inheritance relationship. Motivation Overview Concepts Activities Management Summary

Example An example of a generalization hierarchy Incident LowPriority Overview: An example of a generalization hierarchy Motivation Overview Concepts Activities Incident LowPriority Emergency Disaster EarthQuake ChemicalLeak CatInTree TrafficAccident BuildingFire Management Summary

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

Analysis Activities Main goal: Find the important abstractions Overview: Main goal: Find the important abstractions What happens if we find the wrong abstractions? Iterate and correct the model Steps during object modeling 1. Class identification Based on the fundamental assumption that we can find abstractions 2. Find the attributes 3. Find the methods 4. Find the associations between classes Order of steps Goal: get the desired abstractions Order of steps secondary, only a heuristic Iteration is important Motivation Overview Concepts Activities Management Summary

From Use Cases to Objects Overview: Identifying Entity Objects Identifying Boundary Objects Identifying Control Objects Mapping Use Cases to Objects Modeling Interactions among Objects Identifying Associations Identifying Aggregations Identifying Attributes Modeling Objects State-Dependent Behavior Modeling Inheritance Relationship Reviewing the Analysis Model Motivation Overview Concepts Activities Management Summary

Identifying Entity Objects Overview: Participating objects form the basis of the analysis model. Natural language analysis [Abbott, 1983]. Other heuristics Terms that developers or users need to clarify in order to understand the use case. Recurring nouns in the use cases. Real-world entities that the system needs to track. Real-world activities that the system needs to track. Data source or sinks. Motivation Overview Concepts Activities Management Summary

Identifying Boundary Objects Overview: Boundary objects represent the system interface with the actors. Heuristics Identify the user interface controls that the user needs to initiate a use case. Identify the forms. Identify notices and messages. Identify actor terminals, if multiple users are involved. Do not model the visual aspects of the interface (use mock-ups instead). Always use the end user’s terms for describing interfaces; do not use terms from solution domain. Motivation Overview Concepts Activities Management Summary

Identifying Control Objects Overview: Control objects are responsible for coordinating boundary and entity objects. Heuristics Identify one control object per use case. Identify one control object per actor in the use case. The life span of a control object should cover the extent of the use case or the extent of a user session. If difficult, then the use case is required to be refined. The entry and exit conditions are not well defined. Motivation Overview Concepts Activities Management Summary

Mapping Use Cases to Objects Overview: A sequence diagram ties use cases with objects. It shows how the behavior of a use case (or scenario) is distributed among its participating objects. Heuristics The first column is an actor initiating the use case. The second column a boundary object creating a control object. The third column is a control object managing the rest of the use case. Boundary and control object know about each other. Entity objects do not know about boundary and control objects (independency promotes sharing). Motivation Overview Concepts Activities Management Summary

ReportEmergency Control Example Overview: Sequence diagram for the ReportEmergency use case. Motivation Overview Concepts Activities FieldOfficer Report EmergencyButton ReportEmergency Control ReportEmergency Form Emergency Manage EmergencyControl press() «create» submit() fillContents() submitReport() submitReportToDispatcher() «destroy» Management Summary

Modeling Interactions among Objects Overview: CRC cards Class, Responsibilities, and Collaborators. Initially was introduced as a tool for teaching object-oriented concepts to novices. CRC cards vs. Sequence Diagrams provide different representations for supporting the same type of activity. Sequence diagrams are a better tool for single modeler. CRC cards are better for a group of developers. Motivation Overview Concepts Activities Management Summary

Example Overview: Examples of CRC cards for the ReportEmergencyControl and the Incident classes. Motivation Overview Concepts Activities Management ReportEmer gencyControl Summary Responsibilities Collaborators Collects input from Field- Emer gencyReportForm of ficer Emer gencyReport Controls sequence of AcknowledgementNotice forms during emer gency reporting Incident Responsibilities rack all information related to a single inci- Collaborators Resource T dent.

Identifying Associations Overview: An association shows relationship between two or more classes. A name (optional) A role A multiplicity The associations among entity objects are the most important ones. Heuristics Examine verb phrases. Name associations and roles precisely. Eliminate any redundant association. Do not worry about multiplicity at the beginning. Do not define too many associations. Motivation Overview Concepts Activities Management Summary

Example Overview: An example of association between the EmergencyReport and the FieldOfficer classes. Eliminating redundant association. Motivation Overview Concepts Activities * 1 writes author document FieldOfficer EmergencyReport Management Summary * 1 writes author document triggers reports FieldOfficer EmergencyReport Incident

Identifying Aggregations Overview: Aggregation is a special type of association denoting a whole-part relationship. Composition aggregation indicates that the existence of the parts depends of the whole. Shared aggregation indicates that the existence of the whole and the parts are independent. If you are not sure, then start with a one-to-many association relationship until you are sure about the whole-part relationship. Motivation Overview Concepts Activities Management Summary

Example Examples of aggregations and compositions. State County Overview: Examples of aggregations and compositions. Motivation Overview Concepts Activities State County Township FireStation FireFighter FireEngine LeadCar Ambulance Management Summary

Identifying Attributes Overview: Attributes are properties of individual objects. Consider only the ones relevant to the system. Properties that are represented by objects are not attributes. A name, a brief description, and a basic type. Heuristics Examine possessive phrases. Represent stored state as an attribute of the entity object. Describe each attribute. Objects are not attributes. Use associations. Do not go to details, the object structure is stable. Motivation Overview Concepts Activities Management Summary

Example Attributes of the EmergencyReport class. EmergencyReport Overview: Attributes of the EmergencyReport class. Motivation Overview Concepts Activities Management Summary EmergencyReport emergencyType:{fire,traffic,other} location:String description:String

Modeling State-Dependent Behavior Overview: Sequence Diagrams used to distribute behavior across objects and to identify operations. represent the behavior of the system from the perspective of a single use case. Good for identifying missing objects. Statechart Diagrams represent behavior from the perspective of a single object. Only objects with an extended lifespan and state-dependent behavior are worth considering. Good for identifying missing use cases. Motivation Overview Concepts Activities Management Summary

Example UML statechart for Incident. Overview: Active Inactive Closed Motivation Active Inactive Closed Archived all when d ate > 1yr. resources submitted reports Reported Assessment Disengagement Response field officer arrives on site releases resources dispatcher allocates resources field officer requests additional resources all resources deallocated Overview Concepts Activities Management Summary

Modeling Inheritance Relationship Overview: Generalization is used to eliminate redundancy from the analysis model. if two or more classes share attributes or behavior, the similarities are consolidated into a superclass. An example of inheritance relationship. Motivation Overview Concepts Activities Management Summary FieldOfficer Dispatcher PoliceOfficer badgeNumber:Integer

Reviewing the Analysis Model Overview: The analysis model is built incrementally and iteratively. We say the model is stable, when the number of changes to the model are minimal. Review To make sure that the model is correct, complete, consistent, unambiguous, realistic, and verifiable. internal review after the model is stable, it is first reviewed by the developers. joint review next the model is reviewed jointly by the developer and the client. Motivation Overview Concepts Activities Management Summary

Is Our Model Correct? Overview: Is the glossary of entity objects understandable by the user? Do abstract classes correspond to user-level concepts? Are all descriptions in accordance with the users’ definitions? Do all entity and boundary objects have meaningful noun phrases as names? Do all use cases and control objects have meaningful verb phrases as names? Are all error cases described and handled? Motivation Overview Concepts Activities Management Summary

Is Our Model Complete? For each object: For each attribute: Overview: For each object: Is it needed by any use case? In which use case is it created? Modified? Destroyed? Can it be accessed from a boundary object? For each attribute: When is it set? What is its type? Should it be a qualifier? For each association: When is it traversed? Why was the specific multiplicity chosen? Can association with one-to-many and many-to-many multiplicities be qualified? For each control object: Does it have the necessary associations to access the objects participating in its corresponding use case? Motivation Overview Concepts Activities Management Summary

Is Our Model Consistent? Overview: Are there multiple classes or use cases with the same name? Do entities (e.g., use cases, classes, attributes) with similar names denote similar concepts? Are there objects with similar attributes and associations that are not in the same generalization hierarchy? Motivation Overview Concepts Activities Management Summary

Is Our Model Realistic? Overview: Are there any novel features in the system? Were any studies or prototypes built to ensure their feasibility? Can the performance and reliability requirements be met? Were these requirements verified by any prototypes running on the selected hardware? Motivation Overview Concepts Activities Management Summary

Summary of the Analysis Activities Overview: Review model Consolidate Define interactions associations attributes nontrivial behavior use cases participating objects boundary control entity Motivation Overview Concepts Activities Management Summary

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

Managing Analysis Overview: In the end, the requirements analysis document (RAD) should describe a single coherent system understandable to a single person. Documenting Analysis Assigning Responsibilities Communicating about Analysis Iterating over the Analysis Model Client Sign-Off Motivation Overview Concepts Activities Management Summary

Requirements Analysis Document Overview: 1. Introduction 2. Current system 3. Proposed system 3.1 Overview 3.2 Functional requirements 3.3 Nonfunctional requirements 3.4 Constraints (“Pseudo requirements”) 3.5 System models 3.5.1 Scenarios 3.5.2 Use case model 3.5.3 Object model 3.5.3.1 Data dictionary 3.5.3.2 Class diagrams 3.5.4 Dynamic models 3.5.5 User interface 4. Glossary 1. Introduction 2. Current system 3. Proposed system 3.1 Overview 3.2 Functional requirements 3.3 Nonfunctional requirements 3.4 Constraints (“Pseudo requirements”) 3.5 System models 3.5.1 Scenarios 3.5.2 Use case model 3.5.3 Object model 3.5.3.1 Data dictionary 3.5.3.2 Class diagrams 3.5.4 Dynamic models 3.5.5 User interface 4. Glossary Motivation Overview Concepts Activities Management Summary

Object Models and Dynamic Models Overview: Object Models Section documents in detail all the objects we identified, their attributes, and, when we used sequence diagrams, operations. As each object is described with textual definitions, relationships among objects are illustrated with class diagrams. Dynamic Models Section documents the behavior of the object model in terms of statechart diagrams and sequence diagrams. Although this information is redundant with the use case model, it describes precisely more complex behaviors. Once RAD is completed and published, it will be baselined and put under configuration management. Motivation Overview Concepts Activities Management Summary

Assigning Responsibilities Overview: Roles Generation of Information Integration Review Participants The End User The Client The Analyst The Architect The Document Editor The Configuration Manger The Reviewer Motivation Overview Concepts Activities Management Summary

Participants 1 The End User The client Overview: The End User is the application domain expert. generates information about the current system, the environment of the future system, and the tasks it should supports. Each user corresponds to one or more actors and helps identify their associated use cases. The client funds the project and coordinates the user side of the effort. serves as an integrator of application domain info. defines the scope of the system based on user requirements. Different users may have different views of the system. Motivation Overview Concepts Activities Management Summary

Participants 2 The Analyst The Architect Overview: The Analyst is the application domain expert. Typically a developer with broad application domain knowledge. models the current system and generates information about the future system. Each analyst is initially responsible for detailing one or more use cases. The Architect has an integration role. unifies the use case and object models from a system point of view. Different analyst may have different style of modeling and different view of the parts of the systems for which they are not responsible. provides a system philosophy and detects omissions. Motivation Overview Concepts Activities Management Summary

Participants 3 The Document Editor The Configuration Manager Overview: The Document Editor is responsible for low-level integration of the document and for the overall format of the document and its index. The Configuration Manager is responsible for maintaining a revision history of the document as well as traceability information relating the RAD with other documents. The Reviewer validates the RAD for correctness, completeness, consistency, and clarity. Users, clients, developers, or other individuals may become reviewers during requirements validations. If an individual has not been involved with the system, s/he may provide an excellent review. Motivation Overview Concepts Activities Management Summary

Communicating about Analysis Overview: The information communication is one of the most challenging tasks. Participants with different backgrounds. Stakeholders with different expectations. New teams. Evolving system Approach Clearly define territories (define roles and responsibilities). Clearly define objectives and success criteria. Set up brainstorming meetings. Motivation Overview Concepts Activities Management Summary

Iterating over the Analysis Model Overview: Analysis occurs iteratively and incrementally. Often in parallel with other development activities such as system design and implementation. Steps toward a stable model: Brainstorming Initiated before any other activities. Solidification Once the client and the developers converge on a common idea. Maturity Changes at the higher level are still possible but more difficult, and thus, are made more carefully. Motivation Overview Concepts Activities Management Summary

Client Sign-Off Overview: The client sign-off represents the acceptance of the analysis model by the client. The client and the developers agree about the functionality and features of the system In addition they agree on A list of priorities A revision process A list of criteria that will be used to accept or reject the system A schedule and a budget After the sign-off, the RAD is baselined and is used for refining the cost estimate of the project. Motivation Overview Concepts Activities Management Summary

Prioritizing requirements Overview: High priority (“Core requirements”) Must be addressed during analysis, design, and implementation. A high-priority feature must be demonstrated successfully during client acceptance. Medium priority (“Optional requirements”) Must be addressed during analysis and design. Usually implemented and demonstrated in the second iteration of the system development. Low priority (“Fancy requirements”) Must be addressed during analysis (“very visionary scenarios”). Illustrates how the system is going to be used in the future if not yet available technology enablers are available. Motivation Overview Concepts Activities Management Summary

Example An example of a revision process. Overview: Motivation Report problem or Design change and change request estimate impact Update requirements design Update code (if applicable) Design test Execute all relevant tests Archive request [change approved] Review proposed change Review actual Client Developer Concepts Activities Management Summary

Agenda Motivation Analysis Overview Analysis Concepts Analysis Activities Managing Analysis Summary Motivation Overview Concepts Activities Management Summary

Summary Modeling vs. reality System modeling Overview: Modeling vs. reality System modeling Functional model Object model Dynamic model Object modeling is the central activity Class identification is a major activity of object modeling There are some easy syntactic rules to find classes/objects Requirements Analysis Document Structure Different roles and responsibilities during software development Motivation Overview Concepts Activities Management Summary

Next Session We will spend the next session on your group projects. Overview: We will spend the next session on your group projects. We will work on the requirement analysis document for each project. Please bring your scenarios and use cases as the input for the meeting. Motivation Overview Concepts Activities Management Summary