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Structural Modeling

Structural Modeling. Objectives. Understand the rules and style guidelines for creating CRC cards, class diagrams, and object diagrams. Understand the processes used to create CRC cards, class diagrams, and object diagrams. Be able to create CRC cards, class diagrams, and object diagrams.

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Structural Modeling

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  1. Structural Modeling

  2. Objectives • Understand the rules and style guidelines for creating CRC cards, class diagrams, and object diagrams. • Understand the processes used to create CRC cards, class diagrams, and object diagrams. • Be able to create CRC cards, class diagrams, and object diagrams. • Understand the relationship between the structural and use case models.

  3. Structural Model • A formal way of representing the objects that are used and created by a business system • People • Places • Things • Drawn using an iterative process • First drawn in a conceptual, business-centric way • Then refined in a technology-centric way describing the actual databases and files

  4. Structural Models

  5. Structural Models • Main goal: to discover the key data contained in the problem domain and to build a structural model of the objects Structural Modeling Solution Domain Problem Domain

  6. A Common Language • Structural models create a well-defined vocabulary shared by users and analysts • Classes created during analysis are not the classes that programmers develop during implementation • This refinement comes later • Typical structural models: • CRC cards • Class (and Object) diagrams

  7. Classes • Templates for instances of people, places, or things • Attributes • Properties that describe the state of an instance of a class (an object) • Operations • Actions or functions that a class can perform Classes, Attributes, & Operations

  8. Relationships • Describe how classes relate to one another • Three basic types in UML • Generalization • Enables inheritance of attributes and operations • Aggregation • Relates parts to wholes • Association • Miscellaneous relationships between classes

  9. CRC Cards

  10. Responsibilities & Collaborations • Responsibilities • Knowing • Doing • Collaboration • Objects working together to service a request

  11. Front-Side of a CRC Card

  12. Back-Side of a CRC Card

  13. Class Diagrams

  14. Elements of a Class Diagram

  15. Attribute Visibility • Attribute visibility can be specified in the class diagram • Public attributes (+) are visible to all classes • Private attributes (-) are visible only to an instance of the class in which they are defined • Protected attributes (#) are like private attributes, but are also visible to descendant classes • Visibility helps restrict access to the attributes and thus ensure consistency and integrity

  16. Operations • Constructor • Creates object • Query • Makes information about state available • Update • Changes values of some or all attributes

  17. More Elements of Class Diagrams

  18. Multiplicities Exactly one: A department has one and only one boss Department Boss Employee Child Boss Employee 1 1 Zero or more: An employee has zero to many children 1 0..* One or more: A boss is responsible for one or more employees 1 1..*

  19. More Multiplicities Zero or one: An employee can be married to 0 or 1 spouse Employee Spouse Employee Vacation Employee Committee 1 0..1 Specified range: An employee can take 2 to 4 vacations each year 1 2..4 Multiple disjoint ranges: An employee can be in 1 to 3 or 5 committees 1 1..3, 5

  20. Sample Class Diagram

  21. Domain Model : visualizing concept

  22. Object modeling might support a reduced “semantic gap” in models at different stages. But an exact 1-1 mapping is not always present or desirable.

  23. Not A Diagram of Software Components • Conceptual models represent ideas, things, and objects in the real-world problem domain. • A conceptual model is not a picture of: • Software components. • Classes in an object-oriented programming language. • It illustrates real-world concepts.

  24. 4 Steps to Domain Model • Make a list of candidate concepts • Create CRC Cards • Create the class diagram (Domain Model) • Review the class diagram

  25. STEP 1 Make a list of candidate concepts

  26. Strategies to Identify Conceptual Classes • Use a conceptual class category list • Make a list of candidate concepts • Use noun phrase identification • Identify noun ( and noun phrases) in textual descriptions of the problem domain, and consider them as concepts or attributes. • Use Cases are excellent description to draw for this analysis.

  27. Object Identification • Textual analysis of use-case information • Creates a rough first cut • Common object list • Incidents • Roles

  28. Textual analysis of use-case information • • A Noun • A common or improper noun implies a class of objects. • A proper noun or direct reference implies an instance of a class. • A collective noun implies a class of objects made up of groups of instances of another class. • • An adjective implies an attribute of an object. • • A verb • A verb doing verb implies an operation. • A being verb implies a classification relationship between an object and its class. • A having verb implies an aggregation or association relationship. • A transitive verb implies an operation. • An intransitive verb implies an exception. • A predicate or descriptive verb phrase implies an operation. • • An adverb implies an attribute of a relationship or an operation.

  29. Step 2 Create CRC cards

  30. Designing with CRC cards • CRC Cards—Classes, Responsibilities, Collaboration Cards. • OO design is about assigning Responsibilities to Classes for how they Collaborate to accomplish a use case • Usually a manual process done in a brainstorming session • 3 X 5 note cards • One card per class • Front has responsibilities and collaborations • Back has attributes needed

  31. Detailed Design with CRC cards • Design process • Identify class with primary responsibility • Identify other classes that collaborate with primary class (become requests for service to other classes)‏ • Identify responsibilities within each class (these become methods)‏

  32. CRC Card Notation

  33. CRC Card Results

  34. Step 3 Create Domain Model

  35. Using the CRC card you can identify the following: • Attributes related to each classes. • Association between classes.

  36. Association Category • A is recorded in B • A uses or manages B • A is related to a transaction of B • A communicates with B • A is a transaction related to another transaction B • A is next to B • A is related to B via a transaction • A is recorded in B • A uses or manages B • A is related to a transaction of B • A communicates with B • A is a transaction related to another transaction B • A is next to B • A is related to B via a transaction

  37. Summary • Structural Models • CRC Cards • Class Diagrams • Creating CRC cards and domain model

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