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Re: Attribute markings - a question

From: Steven Pemberton <steven.pemberton@cwi.nl>
Date: Wed, 13 Oct 2021 09:16:32 +0000
Message-Id: <1634115744656.4206433601.512338433@cwi.nl>
To: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, public-ixml@w3.org
Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>
It may be just early in the morning and the coffee hasn't yet kicked in, but I don't see the problem.

I checked in my implementation, making the grammar unambiguous in the process:

	S : @able, baker, @charlie.
	able: string.
	baker: string.
	charlie: string.
	string: ["abc"]*, ".".


	<S able='aaa.' charlie='ccc.'>

Which was what I was expecting.

So assuming I'm not missing something obvious, I suspect that you need to reread the serialisation section of the spec:

A nonterminal attribute is serialised by outputting the name of the node as an attribute, and serialising all non-hidden terminal descendants of the node (regardless of marking of intermediate nonterminals), in order, as the value of the attribute.
which I think covers what you are asking for.

The other side of this coin is:

A nonterminal element is serialised by outputting the name of the node as an XML tag, serialising all exposed attribute descendants, and then serialising all non-attribute children in order. An attribute is exposed if it is an attribute child, or an exposed attribute of a hidden element child (note this is recursive).


On Wednesday 13 October 2021 04:19:52 (+02:00), C. M. Sperberg-McQueen wrote:

> Consider the grammar
> S : @able, baker, @charlie.
> able: string.
> baker: string.
> charlie: string.
> string: ~[]*.
> Is this grammar OK? (Yes, it’s hopelessly ambiguous, but that’s beside the point.)
> If we ignored the annotations, a raw parse tree for this grammar might look like this:
> <S>
> <able mark=“@"><string>aaa</string></able>
> <baker><string>aaa</string></able>
> <charlie mark=“@"><string>ccc</string></able>
> </S>
> Note that ‘string’ is implicitly marked serializable (^).
> When a nonterminal marked to be serialized as an element appears as a child of a nonterminal marked to be serialized as an attribute (as ’string’ here appears as a child of @able and @charlie), is the rule
> - Raise an error because the grammar cannot be serialized that way?
> - Omit the content of ’string’ from the value of @able and @charlie by analogy with what happens when we calculate the text node children of an element?
> - Ignore the marking on ’string’ on the grounds that we have already been told that @able is an attribute. Since elements cannot appear within attributes, the implicid ^ marking on ’string’ is ignored.
> The grammar for ixml offers two examples that seem relevant: in a raw parse tree, @name will dominate nodes labeled namestart and namefollower, which are explicitly marked non-serializable (-). @dstring and @sstring similarly dominate nodes labeled dchar and schar, which are implicitly marked ^. The attributes @from and @to directly dominate nodes labeled ‘character’ (marked -) and indirectly dominate nodes labeled ‘dchar’ and ’schar’ (implicitly ^).
> In the spirit of making things as simple as possible for the grammar authors, I suppose the right rule is “when constructing the value of an attribute, treat nonterminals marked ^ and - the same: recur through them” (the last possibility mentioned above).
> I apologize if this has been discussed before - I have the guilty sensation that it has been, and that I did not retain the answer.
> Michael
Received on Wednesday, 13 October 2021 09:16:52 UTC

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