SNAP is the Software Non-functional Assessment Process.

While function points measure the functional requirements by sizing the data flow through a software application, SNAP measures the non-functional requirements. It is therefore complementary to FPA.

The SNAP model consists of four categories and fourteen sub-categories to measure the non-functional requirements. Non-functional requirement are mapped to the relevant sub-categories. Each sub-category is sized, and the size of a requirement is the sum of the sizes of its sub-categories.

The SNAP sizing process is very similar to the function point sizing process. Within the application boundary, non-functional requirements are associated with relevant categories and their sub-categories. Using a standardized set of basic criteria, each of the sub-categories is then sized according to its type and complexity; the size of such a requirement is the sum of the sizes of its sub-categories. These sizes are then totaled to give the measure of non-functional size of the software application.

Beta testing of the model shows that SNAP size has a strong correlation with the work effort required to develop the non-functional portion of the software application.

Software development evaluation, planning, management, and production control is enhanced when the size and effects of both functional and non-functional application size are considered. Here is where IFPUG holds a unique competitive advantage over other software sizing methods which do not account for non-functional software size.

There is an Excel SNAP Recording tool available, for free.

To download a copy of the tool, navigate to the IFPUG Online Store, Shop for the Top 100 Products, Search for the SNAP Counting Tool, and click on the Go button. There will be two products found:
  • SNAP Counting Tool V2.0.1, for Excel 2003;
  • SNAP Counting Tool V2.0.2, for Excel 2007/2010

Click on the link for the version you want and add it to your cart, then proceed to checkout.

Once you have completed your transaction, while still in the Member Services Area, hover your cursor over My IFPUG Info, Select My Transactions, click My Downloadable Products, and follow the downloading instructions on the page that opens.