- From: Michael Rys <mrys@microsoft.com>
- Date: Thu, 12 Feb 2004 01:19:28 -0800
- To: "Michael Kay" <mhk@mhk.me.uk>, <public-qt-comments@w3.org>
- Message-ID: <EB0A327048144442AFB15FCE18DC96C702053705@RED-MSG-31.redmond.corp.microsoft.com>
Michael Kay is correct. Currently validate provides copy-semantics, thus the new elements are parentless. And this copy semantics is needed because otherwise we start violating the content models of ancestor elements. The update issue is an issue, but node that update only needs to revalidate the newly inserted nodes and just check for the validity of the existing nodes (which does not need to generate new nodes). So I would consider this proposed change to be semantically problematic and don't think it will work. Best regards Michael _____ From: public-qt-comments-request@w3.org [mailto:public-qt-comments-request@w3.org] On Behalf Of Michael Kay Sent: Wednesday, February 11, 2004 5:01 PM To: public-qt-comments@w3.org Subject: RE: [XQuery] IBM-XQ-011: Validation and identity I agree there are usability problems here. But I don't see how two nodes with different attributes can have the same identity, and making nodes mutable at this stage seems too ghastly a prospect to contemplate. I think the current semantics for validate are that the result of validating an element is a parentless element. Michael Kay -----Original Message----- From: public-qt-comments-request@w3.org [mailto:public-qt-comments-request@w3.org] On Behalf Of Don Chamberlin Sent: 11 February 2004 23:52 To: public-qt-comments@w3.org Subject: [XQuery] IBM-XQ-011: Validation and identity (IBM-XQ-011) Section 3.14 (Validate Expression) states that validating a node destroys its identity. I believe that this issue needs more thought. The reason for giving a new identity to a validated node is that some of its contents may change (for example, default attributes may appear). But consider the following: (a) The validated note has the same parent as the original node, right? Doesn't this mean that the content of the parent node has changed? If the parent node can retain its identity, why can't the validated node retain its identity? (b) The working group expects to define update operators that can change the state of a node while preserving its identity. But presumably the updated node will need to be revalidated for type-safety. If validation destroys node identity, how can updates preserve node identity? This seems to violate our XQuery Requirement (3.2.5) that XQuery must be defined in a way that does not preclude the later introduction of update operators. (c) Requiring validation to generate new node identities also raises questions about Requirement (3.4.13) that queries must be able to preserve the identity of items in the Data Model. (d) Requiring validation to generate new node identities also may place an unnecessary burden on implementations that perform incremental validation on the data model rather than serializing it and revalidating the whole tree from scratch. (e) Suppose $n is bound to an element node. Is "$n is validate{$n}" true? Is "$n/.. is validate{$n}/.." true? If the answers are not the same, why not? --Don Chamberlin
Received on Thursday, 12 February 2004 04:19:41 UTC