It must also offer some means by which any input, correctly described in terms of this mechanics, can be used to generate an output which is an equally correct description of the output which the actual system would have given for the input concerned. It must furnish a throughput description mechanics capable of completely defining the first and last throughput states, and perhaps some of the intervening states. In his book The design of engineering systems (1962, p. 25) he stated:Ī functional model must thus achieve two aims in order to be of use. One of the first to define the function model in this field was the British engineer William Gosling. The need to identify and manipulate the properties of a system as a whole, which in complex engineering projects may greatly differ from the sum of the parts' properties, motivated various industries to apply the discipline. The emergence of the field of systems engineering can be traced back to Bell Telephone Laboratories in the 1940s. Gilbreth's tools quickly found their way into industrial engineering curricula. One of those methods was the flow process chart, introduced by Frank Gilbreth to members of American Society of Mechanical Engineers (ASME) in 1921 with the presentation, entitled “Process Charts-First Steps in Finding the One Best Way”. In the late 19th century the first diagrams appeared that pictured business activities, actions, processes, or operations, and in the first half of the 20th century the first structured methods for documenting business process activities emerged. The function model in the field of systems engineering and software engineering originates in the 1950s and 1960s, but the origin of functional modelling of organizational activity goes back to the late 19th century. The purposes of the function model are to describe the functions and processes, assist with discovery of information needs, help identify opportunities, and establish a basis for determining product and service costs.
Example of a function model of the process of "Maintain Reparable Spares" in IDEF0 notation.Ī function model, similar with the activity model or process model, is a graphical representation of an enterprise's function within a defined scope.
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