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Re: [tlaplus] How does TLC know which action is the Init action?



Got it. Thanks.

On Mon, 23 Oct 2023 at 10:07, Hillel Wayne <hwayne@xxxxxxxxx> wrote:

Yup, that's fine, as long as the conjunction of the two predicates fully specifies all variables. So you might do something like

Spec == MachineInit /\ WorldInit /\ [][Next]_vars

Or

Spec == Init /\ DebugInit /\ [][Next]_vars

H

On 10/23/2023 12:03 PM, jayaprabhakar k wrote:
Does that mean, if I have the Spec defined as something like,

Spec == Predicate1 /\ [][Next]_vars /\ WF_vars(Next) /\ Predicate2 
Is it still valid? (Because /\ is commutative)

What are the requirements for a valid init step? For example, any predicate with no unprimed variable. Is that required and is it sufficient? 

Similarly, what if there are two predicates that follow the same requirements, would it be a valid TLA+ spec?

Thanks,
JP


On Mon, 23 Oct 2023 at 02:45, Stephan Merz <stephan.merz@xxxxxxxxx> wrote:
TLC parses the temporal formula, Init is a state predicate and Next is the [1] action that appears within the sub formula [][A]_v.

Stephan

[1] Although in TLA+ it is OK to write specifications that contain more complex formulas, such as [][A]_v /\ [][B]_w, TLC only accepts temporal formulas that contain a single sub-formula of that form.


On 23 Oct 2023, at 11:09, jayaprabhakar k <jayaprabhakar@xxxxxxxxx> wrote:

In TLC we can specify the behavioral spec as a temporal formula spec, and that is typically defined as

Spec === Init /\ [][Next]_vars /\ WF_vars(Next)

In this case,
  • How does TLC know Init is the init function? And more specifically, how does it know Init must happen before any Next operation occurs?
  • Is it by the order in which they are defined or by convention like if the name is Init etc?

Thanks,
JP
 

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