Behaviour Primitives - Special Abstract Machine Definition

Part 4: RSDL Formal Definition

4.5 Special Abstract Machine Definition

4.5.4 Behaviour Primitives

In this section we present the behaviour primitives of the SAM using the macros defined in the previous section as a basis.

We define the domain ACTION for single steps as follows.

ACTION =def ANYORDER ∪ T^ASK ∪ O^UTPUT ∪ C^REATE ∪ S^ET ∪ R^ESET

∪ S^KIP ∪ S^TOP ∪ D^ECISION ∪ V^AR ∪ F^UNCALL ∪ S^YSTEMVALUE ∪ T^IMERACTIVE

∪ C^HECKI^NPUT ∪ C^HECKC^ONTINUOUS

A static domain V^ALUEL^ABEL represents labels in L^ABEL at which an RSDL agent can write or read a value. These values can be accessed by a dynamic, controlled function currentValue.

VALUELABEL =def LABEL CONTINUELABEL =def LABEL

controlled currentValue: VALUELABEL × A^GENT → V^ALUE

The meaning of the evaluation of an action is defined with the macro EVAL. Note that the subdomains of ACTION are pairwise disjoint.

E^VAL(a: A^CTION) ≡

if a ∈ A^NYORDER then EVALANYORDER(a) endif if a ∈ T^ASKthen E^VALT^ASK(a) endif

if a ∈ O^UTPUT then EVALOUTPUT(a) endif if a ∈ C^REATE then EVALCREATE(a) endif if a ∈ S^ET then E^VALS^ET(a) endif if a ∈ R^ESET then EVALRESET(a) endif if a ∈ S^KIP then E^VALS^KIP(a) endif if a ∈ S^TOP then EVALSTOP(a) endif

if a ∈ D^ECISION then EVALDECISION(a) endif if a ∈ V^AR then E^VALV^AR(a) endif

if a ∈ F^UNCALL then EVALFUNCALL(a) endif

if a ∈ SYSTEMVALUE then EVALSYSTEMVALUE(a) endif if a ∈ T^IMERA^CTIVE then E^VALT^IMERA^CTIVE(a) endif if a ∈ C^HECKINPUT then EVALINPUT(a) endif

if a ∈ CHECKCONTINUOUS then EVALCONTINUOUS(a) endif

4.5.4.1 Evaluation in Any Order

Explanation

The any order primitive is used for expressing that some steps can be performed in any order.

Representation

A^NYO^RDER =def L^ABEL-set × C^ONTINUEL^ABEL controlled stillToVisit: AGENT → L^ABEL-set

Behaviour

The function stillToVisit keeps track of all labels that have not been visited. After having visited all labels, this function is reset to undefined for a next call of A^NYO^RDER. If there are still labels to be visited, one of those is chosen and becomes the next label.

EVALANYORDER(a: ANYORDER) ≡

if Self.stillToVisit = undefined then Self.stillToVisit:= a.s-LABEL-set elseif Self.stillToVisit = ∅ then

Self.label:= a.s-CONTINUELABEL Self.stillToVisit:= undefined else

choose l: l ∈ Self.stillToVisit Self.label:= l

Self.stillToVisit:= Self.stillToVisit \ { l }

4.5.4.2 Task

Explanation

The task primitive is used for expressing an assignment.

Representation

T^ASK =def V^ARIABLEN^AME × V^ALUEL^ABEL × C^ONTINUEL^ABEL Behaviour

EVALTASK(task: TASK) ≡

A^SSIGN(task.s-V^ARIABLEN^AME, currentValue(task.s-V^ALUEL^ABEL, Self), Self) Self.label:= task.s-C^ONTINUEL^ABEL

4.5.4.3 Output

Explanation

The output primitive is used for expressing a signal output.

Representation

OUTPUT =def SIGNAL × V^ALUELABEL* × T^OARGLABEL × C^ONTINUELABEL TOARGLABEL =def LABEL

Behaviour

EVALOUTPUT(o: OUTPUT) ≡

SIGNALOUTPUT(o.s-SIGNAL, < currentValue(v, Self) | v in o.s-VALUELABEL-seq >, value2agent(currentValue(o.s-T^OA^RGL^ABEL, Self)) )

Self.label:= o.s-C^ONTINUEL^ABEL Reference Sections

4.5.4.4 Create

Explanation

The create primitive is used for expressing dynamic creation of agent instances at system run time.

Note: There must be a lock that no two instances can be created at the same time (not shown here).

Representation

C^REATE =def C^REATEA^GENTD^EF × C^ONTINUEL^ABEL C^REATEA^GENTD^EF =def Agent-definition

Behaviour

EVALCREATE(c: CREATE) ≡

N^EWA^GENTI^NSTANCE(c.s-C^REATEA^GENTD^EF) Self.label:= c.s-C^ONTINUEL^ABEL

NEWAGENTINSTANCE(agentDesc: Agent-definition) ≡ choose a: a ∈ A^GENT ∧ a.ref = agentDesc

let n = |{ inst ∈ A^GENT: inst.owner = a }| in

if n < agentDesc.s-Number-of-instances.s-Maximum-number then a.offspring := Self // to avoid multiple creation in the same set C^REATEA^GENT(a, Self)

else Self.offspring:= nullAgent Reference Sections

4.5.4.5 Set

Explanation

The set primitive is used for expressing a timer set.

Representation

S^ET =def T^IMEL^ABEL × T^IMERN^AME × C^ONTINUEL^ABEL TIMELABEL =def VALUELABEL

TIMERNAME =def TIMER Behaviour

E^VALS^ET(s: S^ET) ≡

SETTIMER(s.s-TIMERNAME, value2time(currentValue(s.s-TIMELABEL, Self))) Self.label:= s.s-CONTINUELABEL

Reference Sections See also Section 4.5.1.5.

4.5.4.6 Reset

Explanation

The reset primitive is used for expressing a timer reset.

Representation

RESET =def TIMERNAME × C^ONTINUELABEL Behaviour

E^VALR^ESET(r: R^ESET) ≡

RESETTIMER(r.s-TIMERNAME) Self.label:= r.s-CONTINUELABEL Reference Sections

4.5.4.7 Skip

Explanation

The skip primitive is basically a no-op. It is used for instance to model joins.

Representation S^KIP =def L^ABEL Behaviour

E^VALS^KIP(s: S^KIP) ≡ Self.label:= s.s-L^ABEL

4.5.4.8 Stop

Explanation

The stop primitive is used for expressing the stop action.

Representation STOP =defstop Behaviour

E^VALS^TOP(s: S^TOP) ≡

Self.program:= undefined

4.5.4.9 Decision

Explanation

The decision primitive is used for expressing a control flow branching. If none of the alternatives applies, then the further behaviour is undefined.

Representation

D^ECISION =def V^ALUEL^ABEL × A^NSWER-set A^NSWER =def A^NSWERV^ALUE × A^NSWERC^ONTINUE ANSWERVALUE =def LABEL

ANSWERCONTINUE =def LABEL Behaviour

EVALDECISION(d: DECISION) ≡

let dval = currentValue(d.s-VALUELABEL, Self) in

let avalues = { currentValue(a.s-A^NSWERV^ALUE, Self) | a ∈ d.s-A^NSWER-set } in if dval ∈ avalues then

choose a: a ∈ d.s-ANSWER-set ∧ currentValue(a.s-ANSWERVALUE, Self) = dval Self.label:= a.s-A^NSWERC^ONTINUE

elseif undefined ∈ { a.s-A^NSWERVALUE | a ∈ d.s-A^NSWER-set } then choose a: a ∈ d.s-ANSWER-set ∧ a.s-ANSWERVALUE = undefined

Self.label:= a.s-A^NSWERC^ONTINUE else U^NDEFINEDB^EHAVIOUR

4.5.4.10 Evaluation of Variables

Explanation

The V^AR primitive is used for expressing the evaluation of a variable.

Representation

VAR =def VARIABLENAME × C^ONTINUELABEL Behaviour

The value of variableName in the state of the executing agent is determined by the function eval and stored at the current label for Self.

EVALVAR(var: VAR) ≡

currentValue(Self.label, Self) := eval(var.s-VARIABLENAME, Self.state) Self.label := var.s-C^ONTINUEL^ABEL

4.5.4.11 Evaluation of System Values

Explanation

The system value primitive is used to compute the predefined values of RSDL agents.

Representation

SYSTEMVALUE =def VALUEKIND × C^ONTINUELABEL

VALUEKIND =def { nowKind, selfKind, parentKind, offspringKind, senderKind } Behaviour

EVALSYSTEMVALUE(sv: SYSTEMVALUE) ≡ let k = sv.s-VALUEKIND in

if k = nowKind then

currentValue(Self.label, Self):= selector-R^SDLT^IME(now) elseif k = selfKind then

currentValue(Self.label, Self):= agent2value(Self) elseif k = parentKind then

currentValue(Self.label, Self):= agent2value(Self.parent) elseif k = offspringKind then

currentValue(Self.label, Self):= agent2value(Self.offspring) elseif k = senderKind then

currentValue(Self.label, Self):= agent2value(Self.sender) endif

endlet

Self.label:= sv.s-CONTINUELABEL

4.5.4.12 Evaluation of Predefined Functions and Literals

Explanation

The function call primitive is used for evaluating predefined functions and literals.

Representation

F^UNC^ALL =def F^UNCTIONN^AME × V^ALUEL^ABEL* × C^ONTINUEL^ABEL F^UNCTIONN^AME =def Name

Behaviour

E^VALF^UNC^ALL(f: F^UNC^ALL) ≡

currentValue(Self.label, Self) :=

compute(f.s-FUNCTIONNAME, < currentValue(l, Self) | l in f.s-VALUELABEL-seq > ) Self.label := f.s-CONTINUELABEL

Reference Sections See also Section 4.4.4.

4.5.4.13 Evaluation of Timer Active Expressions

Explanation

The timer active primitive is used for expressing the evaluation of timer active expressions.

Representation

TIMERACTIVE =def TIMER × C^ONTINUELABEL Behaviour

E^VALT^IMERA^CTIVE(t: T^IMERA^CTIVE) ≡

currentValue(Self.label, Self) := bool2value(Active(mk-T^IMERI^NST(Self, t.s-T^IMERN^AME))) Self.label := t.s-CONTINUELABEL

Reference Sections See also Section 4.5.1.5.

4.5.4.14 Input Primitives

Explanation

The input primitives are used to model the behaviour of RSDL agents being in a state, i.e. waiting for signals to arrive or for conditions to become true.

Representation

CHECKINPUT =def INPUTDESC-set × S^AVESIGNAL-set × C^ONTINUELABEL SAVESIGNAL =def SIGNAL

C^HECKC^ONTINUOUS =def C^ONTINUOUSS^IGNAL-set × C^ONTINUEL^ABEL Behaviour

E^VALI^NPUT(i: C^HECKI^NPUT) ≡

C^HECKI^NPUTS^IGNAL(i.s-I^NPUTD^ESC-set, i.s-S^AVES^IGNAL-set, i.s-C^ONTINUEL^ABEL) EVALCONTINUOUS(c: CHECKCONTINUOUS) ≡

DOCONTINUOUS(c.s-CONTINUOUSSIGNAL-set, c.s-CONTINUELABEL) Reference Sections

See also Section 4.5.3.1 and Section 4.5.3.2.

Im Dokument Formal Semantics for SDL (Seite 130-135)