The first step in drawing an OV-5 Activity Model is creating the context or A-0 diagram. This diagram depicts the context of a model whose node number is A-n, n being greater than or equal to zero. You create OV-5 context diagrams to describe the system you are modeling in its most complete and abbreviated form.
By IDEF specifications, the context, or A-0, diagram contains one Operational Activity symbol, describing your model’s top-level function (with statements of purpose and viewpoint), and Input, Control, Output, and Mechanism (ICOM) arrows describing the system’s inputs, controls, outputs, and mechanisms.
The OV-5 context diagram has two symbols available:
▪a symbol representing the model (a simple rectangle)
The model symbol is automatically added to the diagram when it is created, if you denote it as a context diagram.
▪a symbol for drawing the operational activity on the diagram (a rectangle with “M” in it).
To create a context diagram
1 First you should have an idea of the model that this IDEF0 Context diagram will represent. You may create a model before hand, or create one as you start the IDEF0 diagram.
2 Ensure that the IDEF0 diagram set is enabled.
To verify IDEF0 diagram capabilities, click Tools > Customize Method Support > Encyclopedia Configuration.
To enable IDEF0 diagrams, click IDEF0 diagram, click OK, and then reopen the encyclopedia.
3 Click Tools > File > New Diagram > OV-5 Activity Model, and type the name of the diagram.
4 Click OK.
5 In the OV-5 Activity Model window, select the Context Diagram checkbox. The number of activities on the diagram is automatically limited to 1.
6 In the Model Name field, type the name of a new model or click the Choices button; then drag an existing model name to the box.
If you type the name of a new model, you can click Define to define the model. You can also do this later. The model should contain information regarding its purpose, scope and viewpoint.
7 Click OK.
A new diagram is created containing a symbol representing the model in its lower‑left corner. The diagram displays one unnamed activity and the IDEF0 Model Name.
Example
The following image shows an example of a context diagram.
Next
From this diagram you can create child, or decomposition, diagrams to develop more detailed views of the function. IDEF0 child diagrams depict several sub-functions to describe the parent function.
