Finding Analysis Classes Written by Zvika Gutterman Adam Carmi

Agenda Objective What are Analysis Classes? Types of Analysis Classes –Boundary classes –Entity classes –Control classes Finding Analysis Classes Example: TVRS Analysis Classes

Objective Identify a candidate set of (analysis) classes which are capable of performing the behavior described in the use cases –The complete behavior of a use case has to be distributed to analysis classes –Non-functional requirements are not taken into account –Concentrate on finding class attributes and relationships

What are analysis classes? The technique for finding analysis classes uses three different perspectives of the system: The boundary between the system and its actors The information the system uses The control logic of the system

What are analysis classes? > = = = A stereotype defines a new model element in terms of another model element.

Types of Analysis Classes > Actor1Actor2 Model interaction between the system and its environment Store and manage information in the system Coordinates the use case behavior

Boundary Classes Models the interaction between the system’s surroundings and its inner workings –User interface classes Concentrate on what information is presented to the user Don’t concentrate on user interface details Example: ViolationsDialog –System / Device interface classes Concentrate on what protocols must be defined. Don’t concentrate on how the protocols are implemented Example: OffendersDBProxy

Boundary Classes (cont.) Boundary classes are environment dependent: –UI dependent –Communication protocol dependent

Entity Classes Models the key concepts of the system Usually models information that is persistent Contains the logic that solves the system problem Is environment independent Can be used in multiple use cases

Control Classes Controls and coordinates the behavior of a use case Delegates the work of the use case to classes –A control class should tell other classes to do something and should never do anything except for directing Control classes decouple boundary and entity classes Often, there is one control class per use case

Control Classes (cont.) Use case and environment dependent Example: –ViolationsController

Finding Analysis Classes 1.For each use case: a.Supplement the use case description b.Identify Boundary, Entity and Control classes c.For each class identified i.Find attributes ii.Find relationships 2.Validate model, repeat process if necessary

Supplement Use Case description The description of each use case is not always sufficient for finding its analysis classes –Entity classes in particular Capture additional information needed in order to understand the required internal behavior of the system that may be missing from the use-case description written for the costumer Focus on enhancing current flow with internal details that realize the external behavior

Identifying Classes Classes may be hidden in: –Requirements document –(Augmented) Use case model –Stakeholder’s Request –Problem domain –Any project documentation

Identifying Classes (cont.) Boundary classes –There should be at least one boundary class for each actor / use-case pair Control classes –Often, there is one control class per use case –If two control classes are similar, their corresponding use cases may need to be merged Example: “manage traffic report” may replace “edit/add/remove traffic report” use cases.

Identifying Classes (cont.) Entity Classes –Identified by examining the nouns and noun phrases in problem description, requirements document, use cases and other documentation –Nouns found may be: Objects Description of an object’s state (attributes) Actors None of the above

Noun elimination Duplicate classes –Differ only in name: “System”, “TVRS”... Irrelevant classes –Classes that have nothing to do with the system (solution): “police headquarters”... Attributes / Operations –Some nouns are likely to be modeled as attributes or operations rather than classes: “ID”, “name”, “Report Lookup”...

Noun elimination (cont.) Roles –Some nouns are roles of objects involved in associations rather than classes Example: “Teaching Assistant” and “Student” may be different roles of a “Person” class. Abstract nouns –“Identify ideas or quantities that have no physical existence” –Rarely end up corresponding to analysis classes, but rather as attributes: “Request”, “Opinion” –May correspond to classes in later design stages

Finding class attributes Properties or characteristics of identified classes –Information retained by identified classes –Atomic Nouns that did not become classes –Information whose value is important for the solution –Information that is uniquely owned by an object

Finding relationships Associations often correspond to verbs or verb phrases –Physical locations: next to, above, inside... –Direct actions: drives, creates, manages... –Communication: talks to, listens, notifies... –Ownership: has, part of, belongs to, contained... –Others: works for, married to, studies at... Eliminate associations that don’t relate to the problem / solution More associations may be discovered using interaction diagrams (introduced later...)

Example: TVRS Analysis Classes Partial noun list from TVRS requirements and use cases (Entity classes candidates): Traffic report Supervisor Report lookup Confirmation TVRS Offender Details Form Traffic report addition System Offender Policeman Vehicle number License number Fault Traffic policeman Commander Violation ID Password Police headquarters Shutdown Date Speed Traffic Violation Clerk

Eliminate duplicate classes Traffic report Supervisor Report lookup Confirmation TVRS Offender Details Form Traffic report addition System Offender Policeman Vehicle number License number Fault Traffic policeman Commander Violation ID Password Police headquarters Shutdown Date Speed Traffic Violation Clerk

Eliminate duplicate classes Traffic report Supervisor Report lookup Confirmation TVRS Offender Details Form Traffic report addition System Offender Policeman Vehicle number License number Fault Traffic policeman Commander Violation ID Password Police headquarters Shutdown Date Speed Traffic Violation Clerk Clerk and Supervisor are replaced by User

Eliminate irrelevant classes Traffic report User Report lookup Confirmation TVRS Offender Details Form Traffic report addition Offender Policeman Vehicle number License number Traffic policeman Commander Violation ID Password Police headquarters Shutdown Date Speed

Eliminate irrelevant classes Traffic report User Report lookup Confirmation TVRS Offender Details Form Traffic report addition Offender Policeman Vehicle number License number Traffic policeman Commander Violation ID Password Police headquarters Shutdown Date Speed

Eliminate attributes and operations Traffic report User Report lookup Confirmation TVRS Offender Details Form Traffic report addition Offender Policeman Vehicle number License number Traffic policeman Commander Violation ID Password Shutdown Date Speed

Eliminate attributes and operations Traffic report User Report lookup Confirmation TVRS Offender Details Form Traffic report addition Offender Policeman Vehicle number License number Traffic policeman Commander Violation ID Password Shutdown Date Speed

Eliminate abstract nouns Traffic report User Confirmation TVRS Offender Details Form Offender Policeman Traffic policeman Violation

Eliminate abstract nouns Traffic report User Confirmation TVRS Offender Details Form Offender Policeman Traffic policeman Violation

Traffic report User TVRS Offender Details Form Offender Policeman Traffic policeman Violation … Entity classes (partial) The remaining list will often contain classes that are not entity classes, such as “Offender Details Form”. Boundary and control classes are easier to find by analyzing use cases directly.

Boundary classes ReportDetailsForm PolicemanDetailsForm LookupReportForm ConfirmationDialog OffendersDBProxy PolicemanDBProxy... A database proxy provides a high-level API and encapsulates communication and query language details

Control classes AddReportController RemoveReportController LookupReportController EditReportController AuthenticationController...

Analysis classes diagram I id : long name : String rank : int Policeman > TrafficPoliceman id : long description : String TrafficReport id : long description : String Violation name : String id : long Offender 1..*1 reports of 1..* issues1* occuredAt : Date

Analysis classes diagram II