Learning Objectives

1
Learning Objectives

• You should be able to
• Describe the evolution of software process models
• Explain the features of each model, I.e., how
  each improves on the previous model
• Discuss the motivation for the CMM, e.g., its
  relationship to software engineering and quality
  improvement
• Compare immature and mature software
  organizations
• List and describe the 5 CMM maturity levels
• Discuss benefits and difficulties in implementing
  the CMM

2
ISM 5316

• Software Process Models and the CMM

3
Software Process Models

• Purpose of software process models
• determine order of stages
• What shall we do next?
• establish transition criteria from one stage to
  the next
• How long shall we continue to do it?
• Model vs. method
• Process vs. product

4
Problems with Software Development Processes

• Late, over-budget, chaotic, undisciplined
• Poor quality software products
• Best results due to individual heroic efforts,
  not mature process
• No consistent long-term productivity
• Difficult to repeat best results
• Larger, more complex projects need a shift from
  technical to management focus
• spent on software increases 12 per year
• Increasing demand for added functionality

5
Code-and-Fix Model

• Steps
• Write some code
• Fix problems in the code
• Think about requirements, design, testing, and
  maintenance later
• Code-driven

• Problems
• Increasingly poorly structured code
• Increasingly expensive to change and fix
• Poor match to users needs, thus increasing the
  need for changing and fixing

6
Stagewise/Waterfall Models
Feasibility
Functional Specifications
Analysis
Detailed Design Specs
Design
Construction
Implementation
Evaluation/ maintenance
7
Difficulties with Waterfall

• Document-driven
• Formal specs may be too much, inaccurate
• Doesnt accommodate
• Parallel or incremental development
• Changing requirements
• Interactive software
• 4GL tools

8
Evolutionary and Transform Models
I cant tell you what I want, but Ill know it
when I see it

• Prototyping
• Iterative development
• Expanding operational software incrementally
• Too much like CodeFix
• Lack of planning
• Lack of structure
• Transform Model
• more structured

Client
9
Spiral Model (Iterative)

• Risk-driven
• (versus document-driven or code-driven)
• Evolutionary and flexible
• Iterative enhancement
• Prototyping risk reduction
• Specifications not uniform, exhaustive, or formal
  less time
• Focuses early attention on reuse
• Incorporates software quality objectives

10
Steps in Each Cycle of Spiral Model

• Objectives
• Constraints
• Alternatives
• Risk identification
• Risk resolution and results
• Plan for next phase
• (Re)commitment

11
Object-Oriented Process Model

• Establish core requirements Conceptualization
• Proof of concept (risk)
• Develop a model of desired behavior Analysis
• develop common vocabulary
• Create an architecture Design
• policies for implementation
• Evolve the implementation Evolution
• refine architecture
• Manage postdelivery evolution Maintenance
• continued evolution based on new requirements

12
Object-Oriented Process
Analysis
Conceptualization
Design
Maintenance
Evolution
13
Current Life-cycle Phases

• Engineering
• Inception (idea)
• Elaboration (architecture)
• Production
• Construction (iterations - beta releases)
• Transition (products)

14
Capability Maturity Model (CMM)

• Helps organizations improve software processes
• Based on results of assessments of contractors,
  industry and govt feedback
• Software process assessment
• assess current capabilities
• highlight high-priority areas for improvement
• gain organizational support for improvement
• Based on Jurans Trilogy of quality improvement
• quality planning, control, improvement
• 5 maturity levels

15
Software Organization Maturity

• Immature
• processes improvised
• reactionary
• unrealistic estimates
• quality compromised to meet schedule
• no objective basis for evaluation
• inadequate review, testing, etc.

• Mature
• standard, documented processes
• known, used, and learned
• organization-wide ability to manage processes
• continuous process improvement
• clear roles and responsibilities
• managers monitor product quality and customer
  satisfaction
• realistic schedules and budgets based on
  historical data

16
CMM Definitions

• Software process
• Activities, methods, practices, and
  transformations used by people to develop and
  maintain software products
• Capability
• Range of expected results achieved by a software
  process
• Performance
• Actual results achieved by a software process
• Maturity
• Extent to which a software process is explicitly
  defined, managed, controlled, effective, and
  consistent

17
CMM Level 1 Initial

• Unstable, chaotic software processes
• Poor planning undermines good software
  engineering practices
• Process capability is unpredictable
• Performance depends on individual capabilities,
  not repeatable
• Procedures are abandoned in crises
• Lack understanding of importance of planning,
  design, reviews, testing

18
CMM Level 2 Repeatable

• Management vs. technical focus
• PM policies and procedures are established,
  PM standards are defined and enforced
• Planning is based on previous experiences
• time, cost estimation
• Effective processes are
• practiced, documented, enforced, trained,
  measured
• Objective Basic management controls

19
CMM Level 3 Defined

• Software processes, both project management and
  software engineering, are standardized and
  documented
• Organization-wide process definition and training
• Projects can tailor processes to their unique
  needs
• processes empower but dont constrain
• Well-defined, consistent processes, have
• readiness criteria, inputs, outputs
• performance standards, completion criteria,
  verification
• Software Engineering process group established
• Common organizational understanding of process
• activities, roles, responsibilities

20
CMM Level 4 Managed

• Quantitative measures of quality
• products and processes
• Organization-wide process database for analysis
  and as basis for measurement
• Narrow variation in process performance
• Risk assessment and management
• Predictable capability

21
CMM Level 5 Optimizing

• Organization-wide focus on continuous improvement
• incremental improvement
• improvement by adoption transfer of innovations
• Goal is defect prevention
• analyze defects to determine causes
• Lessons learned transferred to future projects
• Emulates statistical process control in
  manufacturing systems

22
Strengths and Limitations

• Descriptive, normative model of behavior
• Doesnt constrain unique organizational process
  needs
• Needs to be interpreted, implemented to fit the
  context
• organizations strategic objectives, culture,
  structure, systems
• Assumes other organizational change processes in
  place
• Takes 1 years to move from one level to the next
• Levels should not be skipped
• each provides the foundation for the next one

23
Difficulties in Improving Software Processes

• Lack of consensus between managers and developers
  about how to improve
• Focus on management vs. engineering
• management process harder to define
• Requires time - no quick fix
• Must be done one level at a time
• Requires culture change
• Requires organization-wide commitment
• Scarcity of skilled personnel

24
Benefits of CMM

• Visibility of software process to management
• Predictable performance
• time and cost estimation
• decreases differences in targeted/actual results
  and variability of results
• Better control over new technologies and
  applications
• More efficient communication
• concise, common, quantitative terms
• Disciplined change as a way of life