CS616 – Software Engineering II

Lecture 10

Larman – Part5 – Elaboration: Iteration 3

Chapter 27 – Refining the Domain Model

Objectives

• Add association classes to Domain Model
• Add aggregation relationships
• Model time intervals of applicable information
• Choose how to model roles
• Organize the Domain Model into packages

Association Classes

An association class may be useful in the Domain Model if:

· An attribute is related to an association

· Instances of the association class have a life-time dependency on the association

· There is a many-to-many association between two concepts, and information associated with the association itself.

UML signifies an association using a dashed line:

ServiceContract and its attributes are related to the association between a Store and an AuthorizationService, and lifetime of service contract depends on the relationship

Aggregation and Composition

· Aggregation is a kind of an association used to model whole-part

relationships between things

· The whole is called the composite

· UML shows aggregation with a hollow or filled diamond at the composite end of the relationship:

Composite Aggregation – Filled Diamond

· Composite aggregation (composition) means that the part only belongs to one composite object

· e.g. hand is composition relationship to a finger

· UML: filled diamond – composite solely owns the part:

· If multiplicity end is exactly one, the part may not exist separate from composite.

· If multiplicity end is 0 .. 1, the part may exist separate from composite.

Shared Aggregation – Hollow Diamond

· Shared aggregation means that the multiplicity at the composite end may be more than 1.

· The part may be in many composite instances

Show aggregation when:

· The lifetime of the part is bound within the lifetime of the composite

· There is a logical whole-part physical or logical assembly

· Some properties of the composite propagate to the parts

· Operations applied to the composite propagate to the parts

Aggregation in POS Domain Model

· SalesLineItems are part of a composite Sale

· ProductCatalog is an aggregate of ProductSpecifications

Time Intervals

• Collection of time interval related information needs to maintained
• Associate data with applicable time interval
• e.g. ProductSpecifications and ProductPrices

Association Role Names

· Each end of an association is a role with properties

· e.g.

name

multiplicity

Qualified Associations

· A qualifier may be used in an association

· It distinguishes the set of objects at the far end of the association based on a qualifier value

· An association with a qualifier is a qualified association.

· e.g. ProductSpecifications may be distinguished in a ProductCatalog by their itemID

Reflexive Associations

Concept may have association to itself – reflexive association

Ordered elements

• e.g. SalesLineItems must be maintained in order entered

Using Packages to Organize the Domain Model

• UML package is shown as a tabbed folder

• Ownership and references
• An element is owned by a package within which it is defined, but may be referenced by other packages
• The element name is qualified by the package name using the pathname format

• Ownership and dependencies
• Models may be shown with dependencies

How to Partition a Domain Model into Packages

Place elements together that:

• Are in the same subject area
• Are in a class hierarchy together
• Participate in the same use cases
• Are strongly associated

POS Domain Model

Core/Misc Package

• Core/Misc package useful to own widely shared concepts or those without an obvious home

Products

Chapter 28 – Adding new SSDs and Contracts

Additional SSDs and contracts for current iteration

Chapter 29 – Modeling Behavior in Statechart Diagrams

UML includes statechart diagrams to illustrate the events and states of things

Events, States, and Transitions

• An event is a significant or noteworthy occurrence
• A state is the condition of an object at a moment in time
• A transition is a relationship between two states that indicates when an event occurs

Statechart Diagrams

· UML notation:

• Arrows – transitions
• States – rounded rectangles

· Include initial pseudo-state

· Statechart diagram shows lifecycle of an object

· Statechart diagram applied to – classes, use cases

Use Case Statechart Diagram

• Useful application – describe the legal sequence of external system events that are recognized and handled by system in context of use case.
• e.g. simplified version of Process Sale use case

Classes that Benefit from Statechart diagrams

State-independent and state-dependent objects

• State-independent – responds same way to event
• State-dependent – responds differently depending on state

Common state-dependent Classes

• Use cases
• Stateful sessions (server-side software)
• Systems
• Windows
• Controllers
• Transactions
• Devices
• Role mutators