ISO/IEC 24570:2005

INTERNATIONAL ISO/IEC
STANDARD 24570
First edition
2005-02-15

Software engineering — NESMA
functional size measurement method
version 2.1 — Definitions and counting
guidelines for the application of Function
Point Analysis
Ingénierie du logiciel — Méthode de mesure de la taille fonctionnelle
NESMA, version 2.1 — Définitions et manuel des pratiques de
comptage pour l'application de l'analyse des points fonctionnels




Reference number
ISO/IEC 24570:2005(E)
©
ISO/IEC 2005

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ISO/IEC 24570:2005(E)
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ISO/IEC 24570:2005(E)
Contents Page
Foreword. v
Introduction . vi
1 Scope. 1
2 Overview . 1
2.1 Objective of this International Standard. 1
2.2 Focus of this International Standard. 1
2.3 Organization of this International Standard . 2
3 Introduction to FPA. 3
3.1 Brief description of FPA . 3
3.2 Use of FPA: application function point count versus project function point count . 4
3.3 The types of function point counts . 5
3.4 Function point counts during a project . 5
3.5 Scope of the count and boundary of the application to be counted . 5
3.6 Users . 5
3.7 Functions and function types. 6
3.8 The complexity of a function . 6
3.9 The valuing of function types . 7
3.10 The function point count. 7
4 Guidelines to carry out an FPA. 7
4.1 Step-by-step plan for carrying out an FPA. 8
4.2 Types of function point counts and their accuracy. 8
4.3 The role of the quality of the specifications. 10
4.4 FPA during a project. 11
4.5 Determining the application function point count. 11
4.6 Determining the project function point count. 13
4.7 FPA in specific situations. 16
4.8 Illustration: FPA and the system life cycle . 20
5 General counting guidelines. 25
5.1 Counting from a logical perspective. 25
5.2 Applying the rules . 25
5.3 Built functionality, not requested functionality . 25
5.4 Double counting. 25
5.5 Production of re-usable code . 26
5.6 Re-use of existing code. 26
5.7 Screens and reports. 26
5.8 Input and output records. 26
5.9 Security and authorization . 26
5.10 Operating systems and utilities. 26
5.11 Report generators and query facilities . 27
5.12 Graphs. 27
5.13 Help facilities . 27
5.14 Error messages and other messages .27
5.15 Menu structures . 28
5.16 List functions. 28
5.17 Browse and scroll functions. 28
5.18 Cleaning functions. 28
5.19 Completeness check on the function point count. 29
5.20 FPA tables. 29
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ISO/IEC 24570:2005(E)
5.21 Deriving logical files (data functions) from a normalized data model .30
5.22 Shared use of data .34
6 Internal Logical files.35
6.1 Definition of an internal logical file.35
6.2 Counting internal logical files .36
6.3 Determining the complexity of internal logical files .37
7 External Interface Files .38
7.1 Definition of an external interface file .38
7.2 Counting external interface files.38
7.3 Determining the complexity of external interface files.40
8 External inputs.40
8.1 Definition of an external input.41
8.2 Counting external inputs .42
8.3 Determining the complexity of external inputs .44
9 External Outputs.45
9.1 Definition of an external output .45
9.2 Counting external outputs.47
9.3 Determining the complexity of external outputs.50
10 External inquiries .51
10.1 Definition of an external inquiry.51
10.2 Counting external inquiries.52
10.3 Determining the complexity of external inquiries .53
11 Practical Situations and their solutions.54
11.1 Standard authorization functions .55
11.2 Specific authorization functions.55
11.3 Report generator and query facility.56
11.4 Help functions.56
11.5 Error messages.57
11.6 Menu structures.57
11.7 FPA tables .58
11.8 Denormalization.59
11.9 Counting logical files (data functions).61
11.10 Combined external inputs .65
11.11 Counting a transaction file .66
11.12 Reports on different media.67
11.13 Daily and weekly processing.69
11.14 Conversion.69
11.15 External outputs with summary information.70
11.16 The number of data elements on a report.72
11.17 Combined external outputs.72
11.18 Combination effects with functions .77
11.19 Querying with several search keys.79
11.20 Screens with list function.81
11.21 Browse and scroll functions .82
11.22 Selection screens and changing data with a search key .85
11.23 Direct and delayed processing .89
11.24 Case study of a customer application.91
Annex A (normative) The most important features and tables for valuing function types .95
Annex B (normative) Function point analysis glossary.101
Annex C (informative) Application of function point analysis including general system
characteristics .106
Annex D (informative) General system characteristics.113

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ISO/IEC 24570:2005(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees established
by the respective organization to deal with particular fields of technical activity. ISO and IEC technical
committees collaborate in fields of mutual interest. Other international organizations, governmental and non-
governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO
and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 24570 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 7, Software and system engineering.

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ISO/IEC 24570:2005(E)
Introduction
Version 1.0 (November 1990)
The NESMA Board set up a counting guidelines committee devoted to the standardization of counting
guidelines/definitions in September of 1989. The committee's task was and (still) is to draw up and maintain a
NESMA FPA manual.
Version 1.1 (May 1991)
Version 1.1 is a reprint of version 1.0. Except for the improvement of some minor errors, the two versions are
the same.
Addendum (May 1994)
The manual Definitions And Counting Guidelines For The Application Of Function Point Analysis satisfies a
great need and has become a standard in the Netherlands within a short time.
In May of 1991 the Board of the NESMA set up the work group "FPA Case Study" and gave it the task of
developing a case study that would present the application of FPA and counting guidelines within a context.
While developing the case study, the work group felt that a number of definitions of counting guidelines
needed to be more precise:
• The derivation of logical files from a data model in third normal-form (the so-called denormalization
rules)
• A more concrete definition of the concept of FPA table
• Uniform treatment of selection screens
• Dealing with combination effects of functions
The Counting Guidelines Committee established additional counting guidelines for these topics after extensive
discussion took place both within the committee itself and within the work group FPA Case Study.
You will find the additional counting guidelines necessary and/or helpful when working out the case. In view of
the issue date of the case (mid 1994), the NESMA Board decided to issue these additional counting guidelines
as an Addendum to version 1.1 of the Counting Guidelines Manual.
Version 2.0 (April 1996)
This new version of the manual Definitions And Counting Guidelines For The Application Of Function Point
Analysis incorporates the following improvements:
• The guidelines recorded in the addendum have now been integrated into the manual
• A large number of points in the guidelines have been further clarified
• The results of extensive consultation with the IFPUG have been processed
• The manual's accessibility has been increased further as a result of editorial improvements
• Many examples and illustrations have been added
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ISO/IEC 24570:2005(E)
The committee is of the opinion that the changes made are chiefly an elaboration and further illustration of the
guidelines drawn up earlier. In modifying the manual, the committee has worked in such a way that the
changes made have as little effect as possible on the results of a function point analysis. Appendix D goes
further into this.
The guidelines published in this manual have been applied to a rather large case study with the title, FPA Case
Study "Hotel" For The Application of Function Point Analysis. Applying the guidelines in practice is explained in
this document in detail.
The publication of this version takes precedence over versions 1.0 and 1.1, as well as the Addendum.
English translation of version 2.0 (November 1997)
This English version of the manual is an accurate translation of the Dutch version
Version 2.1 Unadjusted (February 2002)
This version has been developed for the manual to be an ISO recognized standard. The main adaptation is the
exclusion of the General System Characteristics. This exclusion conforms to the ISO standard 14143-1
Functional Size Measurement.
Reason for this International Standard
The NESMA was set up in the spring of 1989. (At that time it was called the NEFPUG.) During its first meeting
in June, it carried out a study among its participants in order to survey which subjects they were interested in.
The standardization of counting guidelines/definitions was high on the list. In reaction to this, the NESMA
Board decided to set up a committee devoted to this topic. This committee set itself the task of putting together
1
a International Standard for the theoretical application and the practical use of function point analysis (FPA) .
Over the years a number of "dialects" have arisen for FPA. These dialects complicate the goal of determining
the number of function points and make it almost impossible for organizations to compare results. One
insufficiently acknowledged reason for this is that different interpretations of the "Albrecht" method have arisen.
This International Standard hopes to provide clarity by formulating standards for the definitions and counting
guidelines that pertain to FPA.
Intended audience
This International Standard is meant for everyone who performs function point counts; i.e., both for people who
count according to the NESMA rules and for those who use the IFPUG rules. For those using the IFPUG rules,
the NESMA International Standard can be a valuable supplement to the IFPUG International Standard if the
differences stated on the website “WWW.NESMA.ORG” are taken into account. The NESMA International
Standard, after all, contains many hints, guidelines, and examples that can be of value to every FPA counter. It
is assumed that the reader has some knowledge of FPA. Nevertheless, we have also attempted to produce as
complete a International Standard as possible that includes sufficient introductory material and explanation for
the new FPA user. For both the maintenance of the IFPUG International Standard and the NESMA
International Standard there is a co-operation between the IFPUG CPC and the NESMA CPC.
Departure points of this International Standard
The NESMA FPA method is in principle applicable to all Functional domains.
The following documentation has served as the foundation for this International Standard:
• IBM CIS & A Guideline 313, AD/M Productivity Measurement and Estimate Validation, November 1,
1984.

1
   The abbreviation FPA is used for the term Function Point Analysis.
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ISO/IEC 24570:2005(E)
This is an internal IBM publication. The method described in it is usually referred to as Albrecht '84.
Future versions
When changes and supplements to this International Standard prove necessary in the future, an entire new
version will be produced

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INTERNATIONAL STANDARD ISO/IEC 24570:2005(E)

Software engineering — NESMA functional size measurement
methode version 2.1 — Definitions and counting guidelines for
the application of Function Point Analysis
1 Scope
This International Standard:
a) specifies a method to measure the functional size of software,
b) gives guidelines on how to determine the components of functional size of software,
c) specifies how to calculate the functional size as a result of the method, and
d) gives guidelines for the application of the method.
2 Overview
This clause provides an overview to the International Standard "Definitions and counting guidelines for the
application of function point analysis". The following questions are answered: What is its aim (subclause 2.1)?
What is its focus (subclause 2.2)? How is it laid out (subclause 2.3)?
2.1 Objective of this International Standard
The International Standard attempts to provide a theoretical framework by presenting definitions and standard
guidelines. It also tries to illustrate the counting guidelines as concretely as possible by using several practical
situations.
2.2 Focus of this International Standard
The International Standard focuses on how the functional size of an application is determined. The
International Standard does not go into any of the aspects that play a role when project budgeting is drawn up
on the basis of this functional size; e.g., productivity standards and productivity attributes. This particular topic
has been described in the manual “Budgeting on the basis of logical design using function point analysis”, also
by the NESMA.
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ISO/IEC 24570:2005(E)
Figure 1 indicates what this International Standard will and will not cover.
Determining / evaluating the costs of a project

Determining the size of an application

Function types Productivity attributes
Internal logical files People
Skills
Methods
External interface files
Techniques
Resources / Tools
External inputs
System environment
Project management
External outputs
User organization
Starting situation
External inquiries
Project type
⇓
function point count

= scope
Figure 1 — Scope of the International Standard
2.3 Organization of this International Standard
The terms and concepts used in the International Standard are explained in Clause 2 and defined in Annex B.
Clause 3 provides an introduction to FPA and in which the functional aspect of FPA is emphasized. It will also
spell out briefly what FPA is and explains the terms that form the basis for the concept of FPA. Matters such
as distinguishing between an application function point count and a project function point count are examined,
just as are other various types of function point counts, the role of FPA during a project, users, and function
point count.
Clause 4 provides you with an overview of the position of FPA in a project and with the types of function point
counts that can be carried out during the life cycle of an application. In other words, the chapter will explain
when points can be counted and what information is needed minimally in order to count. The chapter will also
give a step-by-step plan for carrying out a function point analysis and indicates how projects, applications, and
packages should be counted. Each of these requires their approach.
Clause 5 states general counting guidelines for a function point count.
Clauses 6, 7, 8, 9 and 10 give successively the definitions and guidelines used to identify function types and to
determine the complexity of function types for internal logical files, external interface files, external inputs,
external outputs, and external inquiries. The guidelines are broken down per function type for identifying the
function type concerned, for determining the number of data element types, and for determining the number of
record types or referenced logical files.
Clause 11 provides several practical situations and their solutions. The counting guidelines are not repeated
explicitly here, but reference is made to the relevant guideline(s) or section(s) on which a solution is based.
Annex A is meant to be a short summary of the guidelines and contains the most important features of each
function type, as well as the tables for valuing the function types.
Annex B contains the definitions of the terms that this International Standard uses.
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ISO/IEC 24570:2005(E)
For backward compatibility with previous adjusted function point counts, Annex C describes the application of
FPA with the general system characteristics that lead to a value adjustment factor with which the adjusted
function point count can be determined from the function point count.
Annex D describe
...