Representing Systems II

Seventh Meeting

Class - Associations

Relationships between objects Example:

“on top of” windows is A “on top of” window B

“part of” a drop-down menu ‘is part of’ a window. Other names: aggregation or containment

Class - Multiplicity How many instances of each

of the classes are involved in the relationship.

one-to-one relationship One Status bar “is part of”

One Window one-to-many relationship

Many Drop-down menus “is part of” One Window

many-to-many relationship Many Windows ‘is on top

of’ Many Windows

Building Object Oriented Model

Building object model Identify the classes of objects which make up the system. Define the relationships between the classes. Specify the attributes for the classes.Defining system behavior (Dynamic model) Identify the messages which need to pass between the objects. Assign operations to the different classes.Reference model Defines a collection of standard object classes which can each perform certain

well-defined tasks.

Event Flow Diagram

Specify the flow of messages between objects in response to particular events.

This clarifies which objects are involved in a specific scenario and the part played by each object.

Specification and Description Language

SDL is used to represent real-time systems

SDL systems communicate by passing discrete messages between each other.

Represent distributed parallel systems, system can perform

independent actions simultaneously or concurrently.

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Parallel System

SDL Process SDL Uses processes to describe

the behavior of a system. A process Receives signals while in a ‘state‘ Uses values stored in data variables

to influence its behavior. Stores input signals in a FIFO queue Can be defined to represent non-

deterministic behavior. Process Diagram

A process is represented diagrammatically

The structure of a system is described using system diagrams and block diagrams

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