Software Engineering 2 - Lecture 1

Software Design

Encompasses the set of principles, concepts, and practices that lead to the development of a high quality system or product.

Principles, concepts, and practices

Software Design encompasses the set of _______, _______, and _______ that lead to the development of a high quality system or product.

Design principles

This establish an overriding philosophy that guides the designer as the work is performed.

Design concepts

This must be understood before the mechanics of design practice are applied.

Change continuously

Software design practices ________ as new methods, better analysis, and broader understanding evolve.

Data/Class design
Architectural design
Interface design
Component-level design

Software Engineering Design:

Data/Class design

Transforms analysis classes into implementation classes and data structures.

Architectural design

Defines relationships among the major software structural elements.

Interface design

Defines how software elements, hardware elements, and end-users communicate.

Component-level design

Transforms structural elements into procedural descriptions of software components.

Design; explicit requirements; implicit requirements

The _____ must implement all of the_________ contained in the analysis model, and it must accommodate all of the ________ desired by the customer.

Readable; understandable

The design should be a _______, ________ guide for those who generate code and for those who test and subsequently support the software.

Complete picture of the software

This should be provided in a design, addressing the data, functional, and behavioral domains from an implementation perspective.

Architectural styles or patterns
Well designed components
Evolutionary fashion

A design should exhibit an architecture (a) created using recognizable _________, (b) composed of _______ (c) implemented in an _________.

Modular

A design should be ______.

Distinct representations

A design should contain _______ of data, architecture, interfaces, and components.

Recognizable data patterns

A design should lead to data structures that are drawn from ________.

Functionally independent components

A design should contain_________.

Reduce the complexity of connection

A design should lead to interfaces that ___________ between components and the external environment.

Repeatable method

A design should be derived using a ________ that is driven by software requirements analysis.

Meaningful notation

A design should be represented using ________

Heuristics and notions

Each new software design methodology introduces unique ______

Mechanism
Notation
Heuristics
Guidelines

Common Design Characteristics:

Mechanism

This is for translating the requirements model into a design representation.

Notation

This is for representing functional components and their interfaces.

Heuristics

This is for refinement and partitioning.

Guidelines

This is for quality assessment.

Abstraction
Architecture
Design Patterns
Separation of concerns
Modularity
Information Hiding
Functional independence
Stepwise Refinement
Refactoring
Design Classes

Design Concepts:

Abstraction

This is a named collection of data describing data object, procedural name sequence of instructions with specific and limited function.

Architecture

The overall structure or organization of software components, ways components interact, and structure of data used by components.

Design Patterns

This describe a design structure that solves a well-defined design problem within a specific context.

Separation of concerns

Any complex problem can be more easily handled if it is subdivided into pieces.

Modularity

Compartmentalization of data and function.

Information Hiding

Controlled interfaces which define and enforces access to component procedural detail and any local data structure used by the component.

Functional independence

Single-minded (high cohesion) components with aversion to excessive interaction with other components (low coupling).

Stepwise Refinement

Incremental elaboration of detail for all abstractions.

Refactoring

A reorganization technique that simplifies the design without changing functionality.

Design Classes

Provide design detail that will enable analysis classes to be implemented.

Complete
Primitiveness
High cohesion
Low coupling

Design Class Characteristics

Complete

This includes all necessary attributes and methods and sufficient (contains only those methods needed to achieve class intent).

Primitiveness

Each class method focuses on providing one service.

High cohesion

Small, focused, single-minded classes.

Low coupling

Class collaboration kept to minimum.

Data model

Data objects and database architectures.

Data object

Can be an external entity, a thing, an event, a place, a role, an organizational unit, or a structure.

Data objects

Contain a set of attributes that act as an quality, characteristic, or descriptor of the object.

Interface

Is a set of operations that describes the externally observable behavior of a class and provides access to its public operations.

User interface (UI)
External interfaces to other systems
Internal interfaces between various design components

Important elements of interface design:

UI or User Experience (UX

Is a major engineering action to ensure the creation on usable software products.

Internal and external interface

These should incorporate both error checking and appropriate security features.

Deployment Design Elements

Indicates how software functionality and subsystems will be allocated within the physical computing environment.

Descriptor form deployment diagrams

Show the computing environment but does not indicate configuration details.

Instance form deployment diagrams

Identify specific hardware configurations and are developed in the latter stages of design.