Software Design

Software Design

A process of defining the architecture components interfaces and other characteristics of a system or component and planning for a software solution

Software Architectural Design

Describing software's top-level structure and organization and identifying the various components also called top-level design

Software Detailed Design

Describing each component sufficiently to allow for its construction and specific behavior

Abstraction

A design principle that focuses on essential characteristics while hiding unnecessary details

Coupling

The degree of interdependence between software modules - low coupling is preferred

Cohesion

The degree to which elements within a module belong together - high cohesion is preferred

Decomposition

Breaking down a complex system into smaller more manageable components

Modularization

Organizing software into separate independent modules

Encapsulation

Hiding internal details of a component and exposing only necessary interfaces also called information hiding

Separation of Interface and Implementation

Keeping the interface definition separate from its implementation details

SWEBOK

Software Engineering Body of Knowledge - ISO/IEC TR 19759:2005 standard specifying guide to generally accepted software engineering knowledge

Programming Paradigm

A style or way of programming that defines how to structure and write code

Procedural Programming

Programming paradigm based on procedure calls with step-by-step instructions also called imperative programming - top-down approach

Logical Programming

Programming paradigm based on mathematical logic with facts and rules - declarative approach rather than imperative

Functional Programming

Programming paradigm treating computation as evaluation of mathematical functions avoiding changing state and mutable data

Object-Oriented Programming

Programming paradigm based on objects that encapsulate state and behavior with features like encapsulation inheritance abstraction and polymorphism

Sequence Construct

Programming construct where statements execute one after another in order

Selection Construct

Programming construct that provides choice between alternatives based on conditions like if-then-else

Repetition Construct

Programming construct that causes statements to execute repeatedly until end condition is met like loops

Software Process

A set of related activities that leads to production of a software system

Software Specification

Fundamental activity defining what services are required and constraints on operation

Software Development

Fundamental activity of designing and programming the software

Software Validation

Fundamental activity of checking software meets customer requirements

Software Evolution

Fundamental activity of modifying software to meet changing customer and market needs

Sequential Life Cycle Model

Linear systematic approach to software development progressing through communication planning modeling construction and deployment - also called Waterfall Model

Waterfall Model

Sequential life cycle model with distinct phases flowing downward like a waterfall

Incremental Life Cycle Model

Development broken into mini projects with partial systems successively built - highest priority requirements tackled first

Evolutionary Life Cycle

Combination of iterative and incremental models allowing system to evolve

Spiral Model

Combination of iterative model and SDLC model with execution in cyclic process - focuses on risk analysis

V-Model

SDLC model where execution happens sequentially in V-shape - also known as Verification and Validation model with testing phase for each development stage

Big Bang Model

Simplest model requiring little planning lots of programming and lots of funds - suitable for small projects

Agile Model

Software development approach based on iterative development - swift and versatile

Scrum

Agile framework focused on managing tasks in team-based development with sprints and daily standups

Extreme Programming XP

Agile framework for higher quality software and quality of life - specific engineering practices like pair programming and test-driven development

RAD Model

Rapid Application Development - process based on prototyping without specific planning - less attention to planning more to development

Use Case Modeling

Interaction modeling approach to model interactions between system and external agents

Sequence Diagram

Interaction modeling to show interactions between system components over time

Class Diagram

Structural model showing classes in system and associations between them in object-oriented design

Data Flow Diagram DFD

Graphical representation of flow of data in business information system showing processes data stores flows and external entities

Process in DFD

Receives input data and produces output with different content or form - named with verb followed by singular noun

Data Flow in DFD

Path for data to move from one part of information system to another - can be single element or data structure

Data Store in DFD

Represents data at rest - situation when system must retain data for later use by processes

External Entity in DFD

Person department or outside organization that provides data to system or receives outputs - also called terminators

Context Diagram

Highest level DFD containing only one process representing entire system - Level 0

Level 0 DFD

Context diagram showing system as single process with external entities and major data flows

Level 1 DFD

Explosion of context diagram showing major processes of system - also called Diagram 0

Level 2 DFD

Further decomposition of Level 1 processes showing more detailed sub-processes

Balancing DFD

Ensuring inputs and outputs are conserved between levels of DFDs during decomposition

Top-Down Decomposition

Technique to show more detail in lower-level DFDs - also called leveling

Logical DFD

Describes flow of data to perform business functions - what system does

Physical DFD

Describes implementation of logical data flow - how system does it

HIPO Diagram

Hierarchical Input Process Output - represents hierarchy of modules in software system

IPO Diagram

Input Process Output - depicts flow of control and data in a module

Data Dictionary

Centralized collection of information about data - metadata repository with rigorous definitions

Metadata

Data about data - information describing data characteristics

Data Dictionary Contents

Information about data flows data structures data elements data stores and data processing

Algebraic Notation in Data Dictionary

Equal sign means is composed of - Plus sign means and - Braces for repetitive elements - Brackets for either or - Parentheses for optional

Data Structure

Made up of smaller structures and elements described using algebraic notation

Data Element

Smallest unit of data that has meaning - base or derived

Base Element

Data element initially keyed into system

Derived Element

Data element created by process usually from calculation or decision-making

Structural Record

Group of related data elements like customer name address and telephone

Software Tool

Program that automates labor in management design coding testing inspection or maintenance of programs

Preprocessor

Software tool performing preliminary work on draft program before complete testing

Program Analyzer

Tool that modifies or monitors operation of program to collect information about operating characteristics

Test Data Generator

Tool that analyzes program and produces files of data needed to test program logic

Structured Programming

Developing programs in certain style with standard constructs for easier understanding and maintenance

Top-Down Development

Designing coding and testing by building modules from general level to specialized detailed level

Chief Programmer Team

Team with skilled chief programmer backup programmer and programming librarian

Standard

Published document ensuring reliability of materials products methods or services - establishes requirements specifications and guidelines

ISO

International Organization for Standardization - world's largest developer of international standards

ISO 9001

Standard for quality management systems - can be applied to any organization

Quality Management

What organization does to ensure products satisfy customer quality requirements and comply with regulations

Generic Standard

Standard that can be applied to any organization regardless of size product or sector

Management System

What organization does to manage processes so products meet objectives like customer satisfaction and regulatory compliance

ISO 9000-3

Guideline on how to use ISO 9001 for software development

ISO/IEC/IEEE 12207

International standard for software life cycle processes defining all processes for developing and maintaining software

IEEE 1074

Standard for developing software project life cycle process

Design Constraint

Restriction on design of system or development process that must be fulfilled to meet technical business or contractual obligations

Sources of Design Constraints

Restriction of design options - Conditions on development process - Regulations and imposed standards

Business Constraint

Limits decisions about people processes costs and schedules

Technical Constraint

Limits decisions about technology used in software system

FDA

Food and Drug Administration - regulatory body imposing standards on medical products

FCC

Federal Communications Commission - regulatory body for communications

DOD

Department of Defense - imposes standards on defense systems

UL

Underwriters Laboratory - safety certification organization

Confidentiality

Professional responsibility to respect confidentiality of employers or clients

Competence

Professional responsibility not to misrepresent level of competence or accept work outside competence

Intellectual Property Rights

Professional responsibility to protect patents copyright and IP of employers and clients

Computer Misuse

Professional responsibility not to use technical skills to misuse others computers

ACM IEEE Code of Ethics

Software Engineering Code of Ethics and Professional Practice - standard for teaching and practicing software engineering

Software Engineering Activities

Software specification development validation and evolution

Version Control

Tool for managing changes to source code over time

Building Software

Tools for compiling and creating executable programs

Automated Testing

Tools for automatically testing software for bugs and issues

Deployment Tools

Tools for releasing and installing software in production environments

Monitoring Tools

Tools for tracking software performance and issues in production

Integration Tools

Tools for combining different software components and systems

Context Level Diagram Rules

Must fit on one page - Process name should be system name - Gets number 0

DFD Numbering Convention

Use unique reference numbers - hierarchy of 1 2 3 then 1.1 1.2 1.3 then 1.1.1 1.1.2