- From: Wilson, Kirk D <Kirk.Wilson@ca.com>
- Date: Thu, 26 Jul 2007 10:22:23 -0400
- To: "Lynn, James \(HP Software\)" <james.lynn@hp.com>, "Smith, Virginia \(HP Software\)" <virginia.smith@hp.com>, <public-sml@w3.org>
- Message-ID: <F9576E62032243419E097FED5F0E75F303275EF4@USILMS12.ca.com>
Here's what I have in mind as a potential problem: Assume there is a reference element E which is defined as acyclic. E contains element A (just a property like Name) and the reference scheme. The reference scheme points to an element S. S defines E.A as a key and provides a key reference back to E based on A. Does this structure violate the acyclicity requirement of E? If so, I don't think the text is clear that it is not allowed. On the other hand, if it doesn't violate the requirement, why isn't this a cyclic reference? (Does this make sense?) If this does not make, then my underlying question is, how come key references aren't subject to similar constraints as SML references (esp. acyclicity)? And deeper: what is the scope of the word "reference"? If just SML references, then are key references "references" or not? I think you bring up another good issue: How polymorphic is acyclicity? Yes, polymorphology might have to be an option. Kirk Wilson, Ph.D. Research Staff Member CA Labs 603 823-7146 ________________________________ From: Lynn, James (HP Software) [mailto:james.lynn@hp.com] Sent: Thursday, July 26, 2007 8:31 AM To: Wilson, Kirk D; Smith, Virginia (HP Software); public-sml@w3.org Subject: RE: [w3c sml] Bugzilla Issue: 4639 - Cyclic SML models Kirk, Section 3.3 defines acyclic in terms of edges of a graph which are instances of some type which is derived from sml:refType. I think we might make this a bit more clear, perhaps as part of our effort to separate the Normative from the Non-normative in the spec. One point that is not very clear is whether acyclicity is determinied by exact match, i.e. references of type R, or whether the criterion should include R and all derived types of R. I think a use case could be given for either way, perhpas indicating a need for a "strict" attribut. Jim James Lynn HP Software 610 277 1896 ________________________________ From: public-sml-request@w3.org [mailto:public-sml-request@w3.org] On Behalf Of Wilson, Kirk D Sent: Wednesday, July 25, 2007 7:05 PM To: Smith, Virginia (HP Software); public-sml@w3.org Subject: RE: [w3c sml] Bugzilla Issue: 4639 - Cyclic SML models I have a question on references. What is the scope of 'reference' in this context? Does it include key references or just (SML) reference schemes? Could a cycle be constructed by having a key reference cycle back to an element that is an acyclic SML reference? Kirk Wilson, Ph.D. Research Staff Member CA Labs 603 823-7146 ________________________________ From: public-sml-request@w3.org [mailto:public-sml-request@w3.org] On Behalf Of Smith, Virginia (HP Software) Sent: Wednesday, July 25, 2007 6:22 PM To: public-sml@w3.org Subject: RE: [w3c sml] Bugzilla Issue: 4639 - Cyclic SML models To answer the 2 questions, I posed in the original email - I've spoken to an engineer at HP who worked on an SML validator project last year. He does not see any technical problems in implementing cycles based on elements instead of (or in addition to) cycles based on documents. This verifies Valentina's comment. -- ginny --------------------- Virginia Smith HP Software / BTO R&D 916-785-9940 8000 Foothills Blvd | Roseville | CA 95747 www.hp.com/software ________________________________ From: public-sml-request@w3.org [mailto:public-sml-request@w3.org] On Behalf Of Valentina Popescu Sent: Tuesday, June 26, 2007 12:36 AM To: Smith, Virginia (HP Software) Cc: public-sml@w3.org; public-sml-request@w3.org Subject: Re: Bugzilla Issue: 4639 - Cyclic SML models There is an SML validator implementation in the COSMOS open source project http://www.eclipse.org/cosmos/ <http://www.eclipse.org/cosmos/> and I am leading this team. We did not have any issue with supporting cycles at the element level as opposed to ( or complementing ) document cycles as described by the current specification. Our validator is using a file based SML repository implementation. To be honest, I think that what is missing here are the set of usecases we want to enable with this function. Thank you, Valentina Popescu IBM Toronto Labs Phone: (905)413-2412 (tie-line 969) Fax: (905) 413-4850 "Smith, Virginia (HP Software)" <virginia.smith@hp.com> Sent by: public-sml-request@w3.org 06/25/2007 05:45 PM To <public-sml@w3.org> cc Subject Bugzilla Issue: 4639 - Cyclic SML models This email is to start a discussion on document-based cycles vs. element-based cycles in SML. http://www.w3.org/Bugs/Public/show_bug.cgi?id=4639 In the current SML spec, there is a mismatch in that references are defined as pointing to elements and model cycles are defined based on documents. Since the concept is question (references) are based on elements, it makes sense to me that SML model cycles should be defined based on elements. I see 2 scenarios that pose a problem when testing for cycles according to the current spec. 1) Since a reference can point to an element defined in the same document as the reference, a cycle could exist within a single document but not appear as a cycle in a document-based graph. (false negative) 2) Let's say Document A contains a reference to element X in Document B and Document B contains a reference to element Y in Document A and elements X and Y are not related in any way. This is not really a cycle (of element references) but will appear as a cycle in a document-based graph. (false positive) I think we need to answer the following question: - Are there implementation-related reasons to support document-based graphs but not element-based graphs? (An SML validator implementation must be realistically achievable.) Does anyone have experience with implementing an SML validator (or know someone with relevant experience)? -- ginny ------------------------------------------- Virginia Smith HP Software / BTO R&D 916-785-9940 8000 Foothills Blvd | Roseville | CA 95747 www.hp.com/software
Received on Thursday, 26 July 2007 14:22:29 UTC