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A Spiral Model of Software Development and Enhancement. Barry Boehm Computer, May 1988 text pp34-45. Software Process Model.

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A Spiral Model of Software Development and Enhancement

Barry Boehm

Computer, May 1988

text pp34-45

Software Process Model

  • “The primary functions of a software process model are to determine the order of the stages involved in software development and evolution and to establish the transition criteria for progressing from one stage to the next.”

Who discovered the waterfall model?

  • A. Royce in 1970

  • B. Boehm in 1988

  • C. Fred Waterfall in 1950

  • D. It always existed, someone just named it in 1966

  • E. Every other discipline knew about it long ago


  • Use a life-cycle development model to manage software development

    • The stages become milestones to mark progress


  • How do you decide whether a stage is complete?

    • A. The manager says it is complete

    • B. The team is ready to go on to the next stage

    • C. The team votes on whether it is complete

TRW’s Ada Process Model for Incremental Development of Large Software Systems

Walker Royce

12th ICSE 1990

text pp46-55

Interesting Approach

  • Incremental development

  • Used Ada as spec language as well as implementation

  • Using stubs and drivers to execute partially implemented systems

Software Process

“Software Processes

are software, too”

Leon Osterweil (1987)

software process


  • A process model is a description of the significant aspects of the tasks that are accomplished during the development of software, including the artifacts produced, the agents involved in the activities, and the relationships between these entities.

Rules for PM diagrams

  • Every process must use one or more artifacts and must produce one or more artifacts.

  • There must be an artifact between two consecutive processes.

Testing Fragment

  • The test designer builds test cases using the source code and the documents. The output is a set of tests

  • The test team does testing using the tests from the test designer and the source code producing a test report

Example Fragment

Example - testing

  • shows who is responsible for what tasks

  • shows what information is necessary for a task

  • shows what is produced by a task

  • shows sequences and dependencies of tasks

PM Notations

  • Many possible notations

    • functional diagrams

    • state diagrams

    • petri models

    • textual descriptions

    • “programming languages”

PM - petri net




build t c

test team



test report

Entities in Process Models

  • Activities/Tasks

  • Information

    • Artifacts (Products)

    • Knowledge

  • Agents

    • People, Positions, Roles

  • Constraints

Control Decisions

  • Some PM show control in terms of decisions

Example Fragment with Decision

L3aS20 Group Task

  • Create a process model for a cooking-dinner task.

  • Work in groups of 2-4 only.

  • Turn in at beginning of 2nd hour.

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