Lecture 8 - Design Modeling Techniques

UML Component Diagram

- Class diagram with stereotype <<component>> - Way to identify larger entities - Components are connected by interfaces - Similar in style and concept to architecture diagram

Finite State Machines

- Models system in terms of states, and transitions between those states - Depicted as state transition diagrams: each state is bubble, each transition is labeled arc from one state to another

viewpoints

- different coordinated models, each capturing a subset of the design decisions - views can contain overlapping and related design decision - can be inconsistent if 2 design decisions cannot simultaneously be true

What to Model?

1. What system aspects should be modeled 2. At what level of detail 3. With how much rigor or formality Cost/benefit decisions: The benefits of creating and maintaining software system models must exceed the cost of doing so Need to make lots of smaller designs = We call the subset-model a 'view' and the concern (or criteria) a 'viewpoint'

UML Static Diagrams

Depict static structure Class, Component, Deployment, Interaction overview, Object Package

UML Class Diagram

Depicts static structure of a system Describes classes in OO sense

UML - Associatons

Does not distinguish attributes and relationships, both are properties of a class

UML Interaction Diagrams: Communication

Emphasizes objects and their relationships

UML Interaction Diagrams: Sequence

Emphasizes ordering of events using a lifeline

Traditional Modeling Techniques

Entity-relationship modeling Finite state machines Data flow diagrams

ERM - Attributes

Intrinsic properties; do not depend on each other, they are descriptive

ERM - Relationships

Mutual properties, such as the membership of a person of some organization

Actor

Represents a person or role that will use your system

UML Use Case Diagram

Represents possible ways user will interact with a system Shows high-level activities organized by goal Decompose activities so that there is no redundancy or overlap of activities Included - use case is called every time a basic path is run Extend - the behavior of another use case

UML Dynamic Diagrams

Show what happens during execution Activity, Communication, Composite structure, Sequence, State machine, Timing, Use case

UML State Machine Diagram

Usually allows for local variables of states Has external inputs and outputs Allows for hierarchical states

Entity-Relationship Modeling

entity: distinguishable object of some type entity type: category of entities attribute value: piece of information describing an entity attribute: category of attribute values relationship: association between two or more entities

Relationship Between Objects: Whole-Part

has aggregation of parts into a whole ex/ dog has legs

Relationship Between Objects: Member-of

has relationship between a set and its members (not transitive) ex/ team has players

Relationship Between Objects: Specialization-generalization

is-a expressed in hierarchy ex/ dog is an animal