The basic building blocks of IDEF3 process flow diagram descriptions are Units of Behavior (Operational Activities), junctions, links, referents, and decompositions.
A Unit Of Behavior, or operational activity, is a distinguishable packet of information about an event, decision, act, or process. You describe operational activities with elaboration documents or child diagrams (decompositions).
Elaboration documents
An elaboration document identifies the facts and constraints for an operational activity and gives it a textual description. Every operational activity has an elaboration document associated with it. The elaboration consists of a description of the operational activity in terms of its set of participating objects and their relations.
Numbering of operational activities
If you have automatic numbering turned on (Tools, Preferences, Number), operational activities are automatically numbered as you draw them, according to the rules of IDEF3. You can also manually number an operational activity by opening the operational activity definition dialog box, and typing a number in the Number property on the Symbol tab.
Operational activities created on a child diagram are also automatically numbered. They are given the number of the parent diagram plus a number of their own added after a decimal point.
Referents
Referents allow the analyst to symbolize one of a number of tasks required in the analysis process. Referents are an easy way to express ideas or concepts in lieu of junction types, dashed arrows, or constraint language statements. Referents represent objects or information critical to the completion of a scenario or Process Flow diagram.
Referents allow you to specify the following in the model:
▪Span multiple pages or loop back in a diagram layout (Go To),
▪Refer to a previously defined Operational Activity without duplication of its definition. This indicates that another instance of this Operational Activity occurs at a specific point in the process (without loop back) (Operational Activity),
▪Emphasize the participation of particular objects or relations in a Operational Activity (Object),
▪Tie in specific examples of referenced data or objects (for example, screen layouts) (Elaboration),
▪Associate special constraint sets to junctions; that is, associate an elaboration with a junction to describe additional facts, constraints, or decision logic which limit how that junction works (Junction), and
▪Form references or links between the OV-6a diagram and OV-6b diagrams (Scenario and OSTN).
Links
Links represent relationships (constraints) that exist between Operational Activities.
There are three types of links:
Link
Description
Precedence
Represent simple temporal precedence between the instance of one Operational Activity and another Operational Activity.
Relational
(Also called user-defined links) highlight the existence of a user-defined relationship between two or more Operational Activities.
Object flow
Highlight the participation of an object in two Operational Activity instances and also imply precedence.
Relational and object flow links are used to convey more information than simple temporal precedence between the participating Operational Activities. The special constraints on relational and object flow links are recorded in a link specification document. This specification document is similar to a Operational Activity elaboration.
When you define a link, System Architect creates a link elaboration that specifies what objects are shared between the preceding and the successive Operational Activity in the process description.
Junctions
Junctions describe the flow logic of the process depicted in an OV-6a diagram. In OV-6a, a junction is a point where a Process Flow path branches into multiple paths (Fan-Out), or multiple Process Flow paths merge into one (Fan-In).
A dot will appear in the junction box to indicate it is a fan-in or fan out junction. A dot on the left indicates a fan-in and a dot on the right indicates a fan out.
Junctions may have And, OR, or XOR logic and can be Synchronous or Asynchronous
AND Logic indicates that all proceeding Operational Activities must start (from a fan out) or all prior Operational Activities must complete (into a fan-in)
OR Logic indicates that one or more of the Operational Activities must complete or start depending on if the junction is a fan-in or fan out.
XOR Logic indicates that one and only one of the proceeding or prior processes will start or complete depending on junction type.
Asynchronous fan-in junctions represent junctions where there are no timing constraints placed on the incoming process completions coming into the junction. Synchronous fan-in junctions represent junctions where the incoming processes must complete simultaneously (synchronously) before the Operational Activity following the junction can be activated.