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ACall-and-Continue TS referent attached to a transition arc between states indicates thatthe object must initiate a transition through the states of the referenced TransitionSchematic before the state transition is allowed (see referent discussion in objectschematics subsection).If the referent type is “GO-TO” and it refers to a UOB, the next happening in theprocess is an occurrence of the referenced UOB. This type of referent is often used todocument loops in a process. If the referent type is “GO-TO” and it refers to a Junction,the next happening in the process is an occurrence of the UOB(s) following thereferenced junction. Go-to referents are always Call-and-Continue type referents.Call-and-Wait Referents:If the referent type is “UOB” or “SCENARIO,” it may have an outgoing precedencelink.
Call-and-wait “GO-TO” referents are not permitted.If the referent type is “UOB,” the label must be a UOB label; this means that anotherinstance of a previously-defined UOB occurs at a specific point in the process (withoutloopback).
If this is attached to a transition arc in an object schematic, an activation of49the referenced UOB must be initiated and completed before the state transition is allowed(see referent discussion in object schematics subsection). If this referent type is attachedto an object state in an object schematic, it indicates that the referenced UOB sustains theobject in the state throughout its duration. Further, using a Call-and-Wait referent addsthe constraint that the succeeding object state(s) may not be realized prior to completingthe process represented by the UOB. Similar semantics apply for Scenario-type referentsattached to object states.
See the subsection entitled, “Referents Attached to ObjectStates,” for more detail.If the referent type is “SCENARIO,” the label must be a Scenario label. If thereferent type “SCENARIO” is used in a process schematic, the next happening in theprocess flow is an occurrence of an activation of the referenced Scenario. That is, alldecompositions of the named Scenario would be activated and completed before the nexthappening in the process flow. If a Scenario-type referent is attached to a transition arc inan object schematic, an activation of the referenced Scenario must complete before thestate transition is allowed (see referent discussion in object schematics subsection).If the referent type is “TS,” the label must be a Transition Schematic label. If thisreferent type is used in a process schematic, it must be attached to a UOB with a simpleconnecting link (i.e., no precedence links). This use indicates that the completion of theattached UOB is conditioned on an object transitioning through the referenced TransitionSchematic.
If this referent type is used in an object schematic, it must be attached tosome point on a transition arc between states (i.e., it may not be attached to an object orobject state). A Call-and-Wait TS referent attached to a transition arc between statesindicates that the object must transition through the states of the referenced TransitionSchematic before the state transition is allowed (see referent discussion in objectschematics section below).Using Referents in IDEF3 Process SchematicsIn this section, the use of referents in process schematics is discussed. The use ofreferents in object schematics will be discussed in a later section after introducing thebasic state transition schematics.
This presentation strategy is intended to facilitatediscussion about how to integrate the process-centered and object-centered views of aprocess.Figure 3-35 is a process schematic depicting the requirements planning process. Thereferent in Figure 3-35 (a) indicates that a Transition Schematic (with TransitionSchematic number 1) must be traversed before the Prioritize Needs UOB can initiate inan activation of the process.
This construct reflects the notion that a Statement of Need(SON) traverses through a number of states that must be realized sometime duringmission area analysis. Figure 3-35 (b) demonstrates the use of a Go-To referent to showthe possibility of looping back to the Perform Mission Area Analysis UOB. The junction50referent in Figure 3-35 (c) indicates that the processing after the UOB Explore Concept istransferred to the junction J4 in decomposition 2.1. Referents may also be used toindicate that the situation represented by a UOB box in some other location is to beduplicated at some point. This use of a referent is illustrated in Figure 3-35(d). In theexample, an instance of a process path traversing through the Define Concept UOB isfollowed by the duplication of the processing that occurs in the UOB Perform AlternativeTrade-offs (with UOB number 15 and which is found in decomposition 9.1).(b)(a)GO-TO/PerformMission AreaAnalysisTS/Statementof Need(SON)1/11PerformMission AreaAnalysis1(c)PrioritizeNeeds2ExploreConceptsO3J1GO-TO/XORJ4/2.1(d)DefineConcepts4UOB/PerformAlternativeTrade-offs9.1.15/9.1Figure 3-35Process Schematic with Go-To ReferentsObject SchematicsThis subsection describes how to express detailed object-centered processinformation; that is, information about how objects of various kinds are transformed intoother kinds of things through a process, or how objects of a given kind change statesthrough a process.
Thus, for example, a drive train, a chassis, and an auto body might becombined into a car. Again, in a given heating process, a quantity of water might changestates from frozen, to cold, to warm, to hot, to boiling. An object-centered representationshould, therefore, capture both various kinds of things, as well as kinds of things invarious states.Objects and Object StatesAn object of a certain kind, like a chassis, will be represented simply by a circlecontaining an appropriate label, as illustrated in Figure 3-36. These will be known askind symbols.51AutoBodyChassisFigure 3-36Kind SymbolsA certain kind of object being in a certain state will be represented by a circle witha label that captures the kind itself and a corresponding state, representing thereby thetype, or class, of objects that are in that state (within a given process).
For example,frozen water will be indicated by the label “Water:frozen”, cold water by “Water:cold”,and so on. These new constructs are called object-state symbols, and are illustrated inFigure 3-37.Water:FrozenWater:ColdWater:HotWater:WarmFigure 3-37Object-state SymbolsThe construction of complex representations built from kind symbols and object statesymbols are known as object schematics. The remainder of this section is devoted to thesyntax and semantics of these constructs.
For a lengthy and detailed discussion of thebackground to these constructs and to ontology modeling in general, see the IDEF5Method Report (KBSI 1994).3.3.2Transition SchematicsThe first and most basic construct is the basic state transition schematic (or simply,transition schematic, for short) shown in Figure 3-38.ABFigure 3-38Basic State Transition SchematicIntuitively, a basic transition schematic signifies a certain pattern of events, a certain typeof situation that can occur, namely, a situation in which there is an object a in a givenstate A followed by an object b in state B.
Typically the object a is, over a certain time52Water:Boilingmodified, transformed, or consumed to yield b. More often than not, a and b will be thesame object, such as a quantity of water that transitions from a solid to a liquid state, or agiven car body changing from an unpainted to a painted state. However, this is notalways so; for instance, an incineration process might involve a state transition in which apiece of wood is consumed, yielding a pile of ashes. Hence, for the sake of generality, thedefault semantics of a basic transition schematic is the weaker of the two readings.Should one wish to express the stronger reading explicitly in which one and the sameobject undergoes the state transition, one can use a double headed arrow, as shown inFigure 3-39.5ABFigure 3-39Basic State Transition Schematic with a Strong Transition LinkJust as the transition from A to B typically involves the same object, it is also typicallythe case that the object in state A ceases to be in A prior to its transition to B.
Thus, aquantity of water transitions from solid to liquid; a car body transitions from unpainted topainted; and so on. However, this needn’t always be the case. For example, a room with(at least) one person in it might transition to a room with (at least) ten. That is, a roomwith at least ten people in it is also a room with at least one person in it.In general, then, the semantics of a basic state transition schematic is that, in anoccurrence of the indicated transition, there is first an object a in state A, andsubsequently an object b that comes to be in state B; that is, it is required that a be in stateA before b comes to be in state B.
It is permitted, though perhaps not typical, that theobject in state A be distinct from the object that comes to be in state B; and it is permitted,though perhaps not typical, that a remain in state A after b comes to be in state B.It is important to note that, despite having roughly the same appearance, the semanticsof a solid-tipped arrow in an object schematic is different than the semantics of an arrowin a process schematic.
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