Software Process

Chapter 2 -Process Models

adapted from the book of Dr. Roger S. Pressman

Overview

·         The roadmap to building high quality software products is software process.

·         Software processes are adapted to meet the needs of software engineers and managers as they undertake the development of a software product.

·         A software process provides a framework for managing activities that can very easily get out of control.

·         Modern software processes must be agile, demanding only those activities, controls, and work products appropriate for team or product.

·         Different types of projects require different software processes.

·         The software engineer's work products (programs, documentation, data) are produced as consequences of the activities defined by the software process.

·         The best indicators of how well a software process has worked are the quality, timeliness, and long-term viability of the resulting software product.

Software Process

·         Framework for the activities, actions, and tasks required to build high quality software

·         Defines approach taken as software is engineered

·         Adapted by creative, knowledgeable software engineers so that it is appropriate for the products they build and the demands of the marketplace  

Generic Process Framework

·         Communication

·         Planning

·         Modeling

·         Construction

·         Deployment

Umbrella Activities (applied throughout process)

·         Software project tracking and control

·         Risk management

·         Software quality assurance

·         Formal technical reviews

·         Measurement

·         Software configuration management

·         Reusability management

·         Work product preparation and production

Process Flow

·         Describes how each of the five framework activities, actions, and tasks are organized with respect to sequence and time

·         Linear process flow executes each of the framework activities in order beginning with communication and ending with deployment

·         Iterative process flow executes the activities in a circular manner creating a more complete version of the software with each circuit or iteration

·         Parallel process flow executes one on more activities in parallel with other activities

Task Sets

·         Each software engineering action associated with a framework activity can be represented by different task sets

·         Small one person projects do not require task sets that are as large and detailed as complex projects team oriented project task sets

·         Task sets are adapted to meet the specific needs of a software project and the project team characteristics

Process Patterns

·         Templates or methods for describing project solutions within the context of software processes

·         Software teams can combine patterns to construct processes that best meet the needs of specific projects

Process Pattern Template

·         Meaningful pattern name

·         Forces (environment in which the pattern is encountered and indicators that make problems visible and affect their solution)

·         Type

o   Stage patterns (define problems with a framework activity for the process)

o   Task patterns (define problems associated with engineering action or work task relevant to successful software engineering practice)

o   Phase patterns (define the sequence or flow of framework activities that occur within a process)

·         Initial context (describes conditions that must be present prior to using pattern)

o   What organizational or team activities have taken place?

o   What is the entry state for the process?

o   What software engineering or project information already exists?

·         Solution (describes how to implement pattern correctly)

·         Resulting context (describes conditions that result when pattern has been implemented successfully)

o   What organization or team activities must have occurred?

o   What is the exit state for the process?

o   What software engineering information of project information has been developed?

·         Related patterns (links to patterns directly related to this one)

·         Known uses/examples (instances in which pattern is applicable)

Process Assessment and Improvement

·         Standard CMMI Assessment Method for Process Improvement (SCAMPI) provides a five step process assessment model that incorporates five phases (initiating, diagnosing, establishing, acting, learning)

·         CMM-Based Appraisal for Internal Process Improvement (CBAIPI) provides diagnostic technique for assessing the relative maturity of a software organization

·         SPICE (ISO/IE15504) standard defines a set of requirements for process assessment

·         ISO 9001:2000 for Software defines requirements for a quality management system that will produce higher quality products and improve customer satisfaction

Prescriptive Process Models

·         Originally proposed to bring order to the chaos of software development

·         They brought to software engineering work and provide reasonable guidance to software teams

·         They have not provided a definitive answer to the problems of software development in an ever changing computing environment

Software Process Models

·         Waterfall Model (classic life cycle - old fashioned but reasonable approach when requirements are well understood)

·         Incremental Models (deliver software in small but usable pieces, each piece builds on pieces already delivered)

·         Evolutionary Models

• Prototyping Model (good first step when customer has a legitimate need, but is clueless about the details, developer needs to resist pressure to extend a rough prototype into a production product)
• Spiral Model (couples iterative nature of prototyping with the controlled and systematic aspects of the Waterfall Model)

·         Concurrent Development Model (concurrent engineering - allows software teams to represent the iterative and concurrent element of any process model)

Specialized Process Models

• Component-Based Development (spiral model variation in which applications are built from prepackaged software components called classes)
• Formal Methods Model (rigorous mathematical notation used to specify, design, and verify computer-based systems)
• Aspect-Oriented Software Development (aspect-oriented programming - provides a process for defining, specifying, designing, and constructing software aspects like user interfaces, security, and memory management that impact many parts of the system being developed)

Unified Process

·         Use-case driven, architecture centric, iterative, and incremental software process

·         Attempts to draw on best features of traditional software process models and implements many features of agile software development

·         Phases

o   Inception phase (customer communication and planning)

o   Elaboration phase (communication and modeling)

o   Construction phase

o   Transition phase (customer delivery and feedback)

o   Production phase (software monitoring and support)

Personal Software Process (PSP)

·         Emphasizes personal measurement  of both work products and the quality of the work products

·         Stresses importance of indentifying errors early and to understand the types of errors likely to be made

·         Framework activities

o   Planning (size and resource estimates based on requirements)

o   High-level design (external specifications developed for components and component level design is created)

o   High-level design review (formal verification methods used to uncover design errors, metrics maintained for important tasks)

o   Development (component level design refined, code is generated, reviewed, compiled, and tested, metric maintained for important tasks and work results)

o   Postmortem (effectiveness of processes is determined using measures and metrics collected, results of analysis should provide guidance for modifying the process to improve its effectiveness)

Team Software Process

·         Objectives

o   Build self-directed teams that plan and track their work, establish goals, and own their processes and plans

o   Show managers how to coach and motivate their teams and maintain peak performance

o   Accelerate software process improvement by making CCM Level 5 behavior normal and expected

o   Provide improvement guidance to high-maturity organizations

o   Facilitate university teaching of industrial team skills

·         Scripts for Project Activities

o   Project launch

o   High Level Design

o   Implementation

o   Integration and system testing

o   Postmortem

Process Technology Tools

·         Used to adapt process models to be used by software project team

·         Allow organizations to build automated models of common process framework, task sets, and umbrella activities

·         These automated models can be used to determine workflow and examine alternative process structures

·         Tools can be used to allocate, monitor, and even control all software engineering tasks defined as part of the process model