Functional modeling considers business as function or in other words “a black box”. In functional model function has no temporary sequence but only an entry point and a point of an exit. Functional modeling helps to consider a business model from the point of view of effectiveness, i.e. when modeling we recognize what we have on an entrance, and what we wish to receive at the exit. You can find out more about this subject here https://www.bpmonline.com/l/bpm/definitions/process-modeling.
For example, the company develops some CRM for the business. In case of application of functional approach to modeling already chosen environment for work prompts what to begin with. An entry point we get the entering interest of the client or a lead, an exit point is desirable result which is purchase and receiving the loyal client, receiving the regular customer, receiving most information on the potential client, etc.
Thus, in functional modelling the entry point and desirable result, and the sequence of actions are initially known and are subject to development. At the same time use of functional models as “black boxes” allows to detail each stage as required. And all work when modeling is aimed at finding an optimal solution for achievement of the goal.
You can also use functional models for demonstration of the ideas and versions of decisions. It is also very convenient, in the course of demonstration you can move from the general to details, as it is required to divide and decompose functions.
For example, in the business modelling system function is called process though it isn’t absolutely right. Nevertheless the description of functions and process approach – a little different things. And it is considered that functional modeling is optimum realized in a notation of IDEFO.