Efficient requirements management crucial for a project's success
Non-existing or ineffective requirements management ranks among the main causes for a failure of software projects, as numerous studies verify. This in particular applies to major projects. Requirements management is a process which on the one hand is aligned with the systematic inquiry, organisation and documentation of requirements to a software system. On the other hand if defines how changes in requirements are integrated in existing requirements (change management). The effectiveness of requirements management can be significantly augemnted by using qualified ratios. In this context Function Points can make a valuable contribution.

The problem of changing requirements
In the early stages of a project the requirements to a software system are rarely complete, clear-cut and coherent. Thus it is quite usual that requirements change during the course of a project. In fact changes are unproblematic and to some degree even desirable because at last a product should be developed, in which all concerned stakeholders echo. Changes are not problematic until they are implemented without management control and thus are not included in project planning. Thus the objective of requirements management must be to impede and minimise non-planned enhancements (scope creep) or reductions to the originally defined functional range.

Monitoring changes of the functional range
The Function Points method is an adequate tool to be able to realise and accordingly assess changes at the functional range of a software system. As software functionality can be quantified according to clearly defined standards by the FPA, requirements management has an impartial measurement category whose changes can be monitored during the course of the project. The so-called functional value (= measure for the professionally supported functional range) of the software system is adequately adjusted whensoever new system functionalities are added or existing functions are changed or cancelled. Thus increases or decreases at the functional range can be observed easily. If the functional value is beyond certain tolerance limits compared to the initial value at the beginning of the project, this indicates that it is necessary to adjust the originally planned development effort and that the functional range intended for the concerned software-release should be reconsidered respectively.
The definite functional value of the provided software system can be opposed with the original planned value at the end of the project. Conclusions concerning the effectiveness of applied techniques for requirements enquiries and definition are possible by means of the variance level.

Assessment and prioritisation of change requests
As a change request's scope and its consequences for the project's time and budget planning can be quickly estimated with the aid of Function Points, the Function Points value is an important decision support for assessing and prioritising change requests. Thus the prioritisation of change requests is simplified.
The range of functions which finally had to be revised due to change requests during the course of the project, becomes transperent by Function Points Analysis. Thus it can be illustrated which potential savings could have been achieved by minimising changes during the project's life cycle.

Conclusions
Software functionality can be quantified and thus measured by the Function Point-Analysis. The measurability makes it easier for requirements management to efficiently control changes on the functional range of a software system during the course of the project. Thus the Function Point-Analysis is a valuable control tool for requirements management. Furthermore Function Points provide useful feedback for the identification of improvement possibilities during the devlopment process.

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