Post on 04-Jan-2016
Lecture 6: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.
Understand the relationship between the structural and use case models.
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
Structural Models Main goal: to discover the key data contained
in the problem domain and to build a structural model of the objects
Problem DomainSolution Domain
StructuralModeling
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
Classes, Attributes, & Operations
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
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
Responsibilities & Collaborations Responsibilities
Knowing Doing
Collaboration Objects working together to service a
request
Front-Side of a CRC Card
Back-Side of a CRC Card
Elements of a Class Diagram
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
Operations Constructor
Creates object Query
Makes information about state available Update
Changes values of some or all attributes
More Elements of Class Diagrams
Multiplicities
Department
Boss
Employee Child
Boss Employee
1 1
1 0..*
1 1..*
Exactly one:A department has one and only one boss
Zero or more:An employee has zero to many children
One or more:A boss is responsible for one or more employees
More Multiplicities
Employee Spouse
Employee Vacation
EmployeeCommitte
e
1 0..1
1 2..4
1 1..3, 5
Zero or one:An employee can be married to 0 or 1 spouse
Specified range:An employee can take 2 to 4 vacations each year
Multiple disjoint ranges:An employee can be in 1 to 3 or 5 committees
Sample Class Diagram
Domain Model : visualizing concept
Book
title
public class Book{ private String title; ...}
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.
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.
4 Steps to Domain Model Make a list of candidate concepts Create CRC Cards Create the class diagram (Domain Model) Review the class diagram
STEP 1
Make a list of candidate concepts
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.
Object Identification Textual analysis of use-case information Creates a rough first cut Common object list Incidents Roles
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.
Step 2
Create CRC cards
Designing with CRC cards
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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
Detailed Design with CRC cards
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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)
CRC Card Notation
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CRC Card Results
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Step 3
Create Domain Model
Using the CRC card you can identify the following: Attributes related to each classes. Association between classes.
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