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ISO Standard for Functional Size Measurement


New ISO/IEC International Project Benchmarking Standard Approved

The first part of a 5-part framework for Benchmarking Information Technology was finalised in May 2011 in Paris and has been unanimously approved to become an ISO International standard - ISO/IEC 29155-1

The ISBSG can take credit, as an ISO/IEC:SC7 C Liaison member, for proposing the development of the standard, developing the first draft and providing on-going support for its development.  Former ISBSG president Pekka Forselius (Finland) oversaw the drafting of the text, along with former ISBSG Vice President Pam Morris (Australia) -  and ISBSG technical advisors: Carol Dekkers (USA) and ‘Jacky’ Takahashi (Japan).

Seventeen countries participated in the review of the interim drafts and the final approval vote.  This international collaborative process ensures the result is robust and the outcome is accepted across the IT industry. The ISBSG is already a recognised industry leader in setting standards for data collection. A number of software metrics related tool vendors have adopted the ISBSG data collection and reporting standard and have integrated the ISBSG data set in their tools.

Functional size measurement - what is it?

Organisations engaged in software engineering have struggled for years in search of acceptable quantitative methods for measuring process efficiency and effectiveness, and for managing software costs, for the systems they acquire, develop, enhance or maintain. One critical, and particularly elusive, aspect of this measurement requirement has been the need to determine software size. Numerous software sizing methods have been proposed in the past. These included numbers of source lines of program code and various measures derived from the technical characteristics of the software. These methods have limitations in that they can not be:

  • applied early in the software development process,
  • applied uniformly throughout the software's life time,
  • easily interpreted in business terms, or
  • meaningfully understood by users of the software.

The concept of Functional Size Measurement (FSM) overcomes these limitations by shifting the focus away from measuring how the software is implemented to measuring size in terms of the functions required by the user. The first method to develop this concept was Function Point Analysis developed in 1979 by A. Albrecht of IBM. Since the public release of Function Point Analysis, many sizing methods have been developed based on its concepts. Differing interpretations of the original concepts have resulted in inconsistencies amongst the various sizing methods. These inconsistencies lessened the ability and attractiveness of any of these methods to be a used as a standard method for the functional sizing of software.

Read more information on the ISO Standard for Functional Size Measurement

ISO 12207 and ISBSG Effort Phase map

The following table is provided as a guide for those organisations that use the ISO 12207 standard.

ISO 12207 Project Steps

(Steps in ISO 12207 – Software Engineering Lifecycle Processes)

ISBSG Effort Phase
1 Requirements Elicitation Specify
2 System Requirements Analysis Specify
3 System Architecture Design Specify
4 Software Requirements Analysis Specify
5 Software Design Design
6 Software Construct (Code & Unit Test) Build
7 Software Integration Build
8 Software Testing Test
9 System Integration Test
10 System Testing Test
11 Software Installation Implement
12 User Support Implement




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ISO Standard for Functional Size Measurement - ISO Standard for Functional Size Measurement | iso/iec 14143 | Functional Size Measurement
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