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AW: ISSUE-66 (Semantics of actions): Operational semantics of actions as covered by PRD? [PRD ]

From: Adrian Paschke <adrian.paschke@biotec.tu-dresden.de>
Date: Tue, 24 Jun 2008 16:34:55 +0200
To: "'Rule Interchange Format Working Group WG'" <public-rif-wg@w3.org>
Message-Id: <20080624143447.24F0670000E0@mailserver.biotec.tu-dresden.de>

>- What should is the intended semantics of the actions covered by PRD?

A set theoretic definition on the state and the state which follows from the action.

(I would prefer a writing "w \ {f}" instead of "w-f" to denote the set difference)


>- If (when) PRD covers some kind of Modify action, how should the intended >semantics differ from Retract+Assert?

Then semantics of modify could be given in terms of the semantics of retract and assert which are combined in an atomic (complex) action

>- Any kind of Execute action is, by definition, opaque: how should its >semantics be specified, esp. wrt possible side effects on the state of >facts wrt which the semantics of a PR system is specified in PRD?

The current definition of the semantics of Execute is not clear.

>From the text:

"Given an expression f and a set of ground instances w, Eval(f, w) denotes the set of ground formulae that results of evaluating f in the context of w. The expression, f, is evaluated as a black-box: any side-effect of the evaluation, on w or otherwise, depends only on the specification of the semantics of f."

∀ w ⊆ P(W), w + EXECUTE(f) →RIF-PRD w' = Eval(f, w);

Shouldn't we say

∀ w ⊆ P(W), w + EXECUTE(f) →RIF-PRD w = Eval(f, w);

That is the evaluation should preserve the original set of ground instances, i.e. without side effects. Or, if Execute has side effects and only denotes new ground instances, then it should be 

∀ w ⊆ P(W), w + EXECUTE(f) →RIF-PRD w' = w  ∪ Eval(f, w);


Another question (from the my eMail about syntax) is about the use of External instead of Execute (maybe distinguished by an attribute). A typical example is e.g. a println built-in which can be used in the body of a rule (External?) or the head of a rule (Execute?).


- Adrian


-----Ursprüngliche Nachricht-----
Von: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org] Im Auftrag von Rule Interchange Format Working Group Issue Tracker
Gesendet: Freitag, 20. Juni 2008 18:08
An: public-rif-wg@w3.org
Betreff: ISSUE-66 (Semantics of actions): Operational semantics of actions as covered by PRD? [PRD ]



ISSUE-66 (Semantics of actions): Operational semantics of actions as covered by PRD? [PRD ]

http://www.w3.org/2005/rules/wg/track/issues/

Raised by: Christian de Sainte Marie
On product: PRD 

- What should is the intended semantics of the actions covered by PRD?
- What when the intended action is the creation or the deletion of an individual (object): is that part of the semantics of Assert/Retract? How?
- If (when) PRD covers some kind of Modify action, how should the intended semantics differ from Retract+Assert?
- Any kind of Execute action is, by definition, opaque: how should its semantics be specified, esp. wrt possible side effects on the state of facts wrt which the semantics of a PR system is specified in PRD?
- etc...
Received on Tuesday, 24 June 2008 14:35:41 GMT

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