Softgoals are goals that are hard to express, but tend to be global qualities of a software system.
In order to reduce the number to a manageable quantity, structuring is a valuable approach.
The SNAP model consists of four categories and fourteen sub-categories to measure the non-functional requirements.
Within the application boundary, non-functional requirements are associated with relevant categories and their sub-categories.
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.
[1] Mylopoulos, Chung, and Yu: “From Object-oriented to Goal-oriented Requirements Analysis" Communications of the ACM, January 1999 [CACM.f.doc [1] [2] Götz, Rolf; Scharnweber, Heiko: "IVENA: Integriertes Vorgehen zur Erhebung nichtfunktionaler Anforderungen".