Guide to Choosing a Functional Size Method

There are currently four FSM Methods approved by the International Organisation for Standardisation (ISO). SCOPE currently records IFPUG Functional Size, but it planned to incorporate COSMIC FSM in future versions:

ISO has recently published a guide to choosing the method most appropriate for your needs (ISO/IEC 14143: Part 6) . Key points needed to be considered are the following:

How hard is it to measure Functional Size?

Functional Size measurement requires specialised training of 2 to 3 days duration. After training, it typically takes several months of using the technique, measuring in a variety of situations to become proficient. International accreditation usually requires the measurer to have a skill level of at least 2 years experience in using the technique. Most organisations train a select group of software developers for the measurement role. It is similar to other specialist activities e.g. Database Design, it takes a person skilled in business analysis and attention to detail to make a good Functional Size Measurement Specialist.

How do we effectively manage the Functional Size Results?

Whilst Functional sizing can be performed by recording the results in a spreadsheet, experience shows that this approach has proved to be very high risk which are mitigated by using a specialist FSM tool such as SCOPE Project Sizing Software®. Problems we have experienced with clients using spreadsheets are as follows: