Software Construction: System Behavior and Diagrams

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Questions and Answers

What do actors in SSD represent?

Internal system components

Domain objects in the system

Entities that interact with the system from outside (correct)

System events generators

What is the purpose of Operation Contracts in SSD?

To define system behavior in terms of state changes (correct)

To represent system events in sequence

To model domain objects

To describe system operations without context

What is represented by a dashed line in SSD?

Lifeline (correct)

System Boundary

Actor

Event

What do pre-conditions in Operation Contracts describe?

Assumptions about system state before operation execution Signup and view all the answers

What is the primary focus of SSD?

Events that cross the system boundary Signup and view all the answers

What do post-conditions in Operation Contracts describe?

State of system after operation execution Signup and view all the answers

What is the role of Operation Contracts in SSD?

To define system behavior Signup and view all the answers

How are systems treated in SSD?

As a black box Signup and view all the answers

What is system behavior?

A description of what a system does, without explaining how it does it Signup and view all the answers

What does a system sequence diagram illustrate?

The events that external actors generate, their order, and inter-system events Signup and view all the answers

What is the main difference between standard sequence diagrams and system sequence diagrams?

Standard sequence diagrams show the progression of events over a certain amount of time, while system sequence diagrams present sequences for specific use cases Signup and view all the answers

What is the purpose of a system sequence diagram?

To illustrate input and output events related to the system under discussion Signup and view all the answers

What does an object in a system sequence diagram represent?

A class, or object, in UML Signup and view all the answers

What is the relationship between SSDs and use case diagrams?

SSDs are part of the Use-Case Model, which represents a user's interaction with the system Signup and view all the answers

What notation style is used in system sequence diagrams?

UML Signup and view all the answers

What is the main purpose of a use case diagram?

To represent a user's interaction with the system Signup and view all the answers

Study Notes

System Behavior

System behavior describes what a system does, without explaining how it does it.
A system sequence diagram (SSD) is a fast and easily created artifact that illustrates input and output events related to the systems under discussion.

System Sequence Diagrams (SSDs)

A SSD is a picture that shows, for a particular scenario of a use case, the events that external actors generate, their order, and inter-system events.
SSDs are a type of sequence diagram in UML, following the Unified Modeling Language style and notation.
SSDs show sequences for specific use cases, unlike standard sequence diagrams that show progression of events over time.

SSD vs. Sequence and Use Case Diagrams

Standard sequence diagrams show progression of events over time.
Use case diagrams represent a user's interaction with the system.
SSDs are part of the Use-Case Model, visualizing interactions implied in the use cases.

SSD Notations

Objects are represented by a box shape with an underlined title, modeling the system as a black box.
Actors are represented by stick figures, showing entities that interact with the system.
Events are represented by dashed lines (lifelines), showing system events generated by actors.

SSD Example

SSD treats all systems as a black box, emphasizing events that cross the system boundary from actors to systems.

Operation Contracts

Contracts for operations help define system behavior, describing the outcome of executing a system operation in terms of state changes to domain objects.
Contracts describe detailed system behavior in terms of state changes to objects in the Domain Model, after a system operation has executed.

Operation Contracts Components

Pre-conditions are conditions that the state of the system must satisfy before the execution of the operation.
Post-conditions are conditions that the system state has to satisfy after the execution of the operation.

Operation Contracts Schema

Operation: name of operation (parameters)
Cross Reference: the Use Cases in which the OC occurs
Preconditions: notable assumptions about the state of the system or objects in DM before execution
Postconditions: state of objects in DM after execution of operation

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Description

This quiz covers system behavior, system sequence diagrams, and operation contracts in software construction. It's part of week 11 of the SWE202 course.