What is a functional model?

A functional model is a structured representation of the functions, behaviors, activities or processes of the system or product you want to design or enhance. It describes the functions and processes, assists with the discovery of requirements, and establishes a basis for determining manufacturing and service costs.

This model may comprise functions, transformations, activities, actions, tasks, and other components. The design analysts develop this model and create a data flow diagram. This modeling activity is referred to as creating a functional decomposition. If appropriate, you can use mathematical techniques or simulations to describe the relationships between components of the model and how they interact.

You represent components with building blocks in the diagrams and create trace links between the blocks to indicate how they relate to one another. After you identify components and their relationships, you can assign requirements to them. Functions satisfy the functional requirements of the product; each function may satisfy more than one functional requirement.

You normally express a function as a verb and an object, for example, maintain clearance or transport material.

A functional model is independent of a particular discipline such as software development or mechanical design. It supports the collaboration and defines what the product must do. Simultaneously, you can create a set of abstract solution models (logical models) that are organized into a subsystem decomposition and contain discipline-specific abstract solution elements. These two models evolve together and can generate technical constraints or additional or more detailed requirements.

The link between a function and a logical element can be represented as a realized by relationship or an allocated to relationship, indicating the function is allocated to a specific solution element.