The Simple Function Point method

The Simple Function Point method was designed by Roberto Meli in 2010 to be compliant with the ISO14143-1 standard and compatible with the International Function Points User Group (IFPUG) Function Point Analysis (FPA) method.

The original method (SiFP) was presented for the first time in a public conference in Rome (SMEF2011) The method was subsequently described in a manual produced by the Simple Function Point Association: the Simple Function Point Functional Size Measurement Method Reference Manual, available under the Creatives Commons Attribution-NoDerivatives 4.0 International Public License.

In 2019, the Simple Function Points Method was acquired by the IFPUG, to provide its user community with a simplified Function Point counting method, to make functional size measurement easier yet reliable in the early stages of software projects.

The SPM (Simple Function Point Practices Manual) was published by IFPUG in late 2021.

[2] However, IFPUG FPA had (and still has) a few shortcomings: To overcome at least some of these problems, the SFP method was defined to provide the following characteristics: The sought characteristics were achieved as follows: IFPUG FPA requires that [2] Of these activities, SFP requires only the first two, i.e., the identification of logical data files and transactions.

Activities 4) and 5) are the most time consuming, since they require that every data file and transaction is examined in detail: skipping these phases makes the SFP method both quicker and easier to apply than IFPUG FPA.

In practice, only the concepts of logical data file and transaction have to be known.

Finally, the weights assigned to data files and transactions make the size in SFP very close to the size expressed in Function Points, on average.

Similarly, transactions are named Elementary Process (EP).

Unlike in IFPUG FPA, there is no classification or weighting of the Base Functional Components (BFC as defined in ISO14143-1 standard).

Empirical studies have been carried out, aiming at In the original proposal of the SiFP method, a dataset from the ISBSG, including data from 768 projects, was used to evaluate the convertibility among UFP and SiFP measures.

Another study [5] also used an ISBSG dataset to evaluate the convertibility among UFP and SiFP measures.

This study used data from only 25 Web applications, so it is possible that the conversion rate is affected by the specific application type or by the relatively small size of the dataset.

In 2017, a study evaluated the convertibility between UFP and SiFP measures using seven different datasets.

In conclusion, available evidence shows that one SiFP is approximately equivalent to one UFP, but this equivalence depends on the data being considered, besides being true only on average.

Considering that the IFPUG SFP basic elements (EP, LF) are totally equivalent to the original SiFP elements (UGEP, UGDG), the previous results hold for the IFPUG SFP method as well.

IFPUG FPA is mainly used for estimating software development effort.

Therefore, any alternative method that aims at measuring the functional size of software should support effort estimation with the same level of accuracy as IFPUG FPA.

To perform this verification, an ISBSG dataset was analyzed, and models of effort vs. size were derived, using ordinary least squares regression, after log-log transformations.

It turned out that the two models yielded extremely similar estimation accuracy.

A following study analyzed a dataset containing data from 25 Web applications.

[6] Ordinary least squares regression was used to derive UFP-based and SiFP-based effort models.

Also in this case, no statistically significant estimation differences could be observed.

The introduction to Simple Function Points (SFP) from IFPUG.