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Annex 1 Constructive Cost Model (CoCoMo)  

  Constructive Cost Model (CoCoMo)

  • 1 Identification/Definition of the Method
  • 2 Brief Characteristic of the Method
  • 3 Appraisal of the Method
  • 4 Application of the Method in the V-Model
  • 5 Interfaces
  • 6 Further Information
  • 7 Literature
  • 1 Identification/Definition of the Method

    /Boehm, 1981/

    2 Brief Characteristic of the Method

    CoCoMo (Constructive Cost Model) was developed by Barry W. Boehm; it is a combination of parametric estimation equation and weighting method. Based on the estimated instructions (Delivered Source Instructions DSI), the effort is calculated by taking into consideration both the attempted quality and the productivity factors.

    CoCoMo is based on the traditional top-down programming and concentrates on the number of instructions. It is comprised of three levels:

    1. Basic CoCoMo
      By means of parametric estimation equations (differentiated according to the different system types) the development effort and the development duration are calculated on the basis of the estimated DSI.

      The breakdown to phases is realized in percentages. In this connection it is differentiated according to system types (organic-batch, semidetached-on-line, embedded-real-time) and project sizes (small, intermediate, medium, large, very large).

    2. Intermediate CoCoMo
      The estimation equations are now taking into consideration (apart from DSI) 15 influence factors; these are product attributes (like software reliability, size of the database, complexity), computer attributes (like computing time restriction, main memory restriction), personnel attributes (like programming and application experience, knowledge of the programming language), and project attributes (like software development environment, pressure of development time). The degree of influence can be classified as very low, low, normal, high, very high, extra high; the multipliers can be read from the available tables.
    3. Detailed CoCoMo
      In this case the breakdown to phases is not realized in percentages but by means of influence factors allocated to the phases. At the same time, it is differentiated according to the three levels of the product hierarchy (module, subsystem, system); product-related influence factors are now taken into consideration in the corresponding estimation equations.

    3 Appraisal of the Method

    Criteria for the Application of Method CoCoMo

    Strong and Weak Points of the Method and possible Remedial Measures

    4 Application of the Method in the V-Model

    5 Interfaces

    - not applicable -

    6 Further Information

    Further Developments/Versions

    CoCoMo has already been modified in several ways. Various versions exist with regard to, e. g.

    Related Methods

    In literature (mostly generated prior to CoCoMo) a great number of parametric equations like "effort = a * (KDSI) b" exist for effort estimation-similar to the Basic CoCoMo and with exactly the same disadvantage of being inaccurate. To name only a few authors in this connection: Nelson (1978), Freburger-Basili (1979), Herd (1977), Frederic (1974), Phister (1979), Jones (1977), Halstead (1977), Schneider (1977). The equation factors have a very wide band width (a: between 0,7 and 5,3; b: between 0,98 and 1,83) and Basic CoCoMo-just like these methods-cannot be realized alone.

    7 Literature

    /Boehm, 1981/ Original Literature
    /Noth, 1986/ Definition and Introduction into FPM, Appraisal, Further Developments,
    and Application Proposals (pp. 89-105, p. 118)
    /Reifer, 1989/ Description of Method ASSERT-R as compared to other Estimation Methods
    /Sneed, 1987/ Explanation of the CoCoMo Method as compared to FPM
    and Component Analysis Method (pp. 73-74, p. 174, pp. 177-179,
    pp. 183-186, pp. 193-195, pp. 199-201)

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