The Function Block Diagram (FBD) is a graphical language for programmable logic controller design, that can describe the function between input variables and output variables. A function is described as a set of elementary blocks. Input and output variables are connected to blocks by connection lines.

Functional Analysis and Allocation is a top-down process of translating system-level requirements into detailed functional and performance design criteria. The result of the process is a defined Functional Architecture with allocated system requirements that are traceable to each system function.

The functional analysis is the integration of assessment results into a clinical case conceptualization about a client’s problems and all variables functionally related to those problems.