In general, a function is an operational process performed by an API. This chapter focusses on the technical functions, while the chapter Domain specific functions describes the functional functions. On the highest level functions (in SIVI AFS) are divided into two main categories: functional and technical. These categories are divided into clusters (for example message). But the combination of a category and a cluster still does not define a function. In order to define a function it is necessary to assign an operation (for example new or retrieve) and a variant (for example list) to this combination of category and cluster. Extra information on this topic is available here.