Kurt, could you expand on what you think might be the advantages of a
format such as your example ?
(<?xml version="1.0"
encoding="UTF-8"?>,"foo",5^positiveInteger,<bar><bat/></bar>,<!--
foo -->)
I'm not at all opposed to multiple new serialization formats, although
I'm inclined to think getting *one* more with any decent adoption is a
ambitious goal, let alone 2.
Your example with RNG is interesting, but I don't think its quite a
parallel. With RNG the non-xml form is intended to be authored by
humans, with a design goal of simple human editable representations.
In this case, so far none of the design goals (or use cases) I've come
up with yet involve humans authoring the data.
In your example, what is the design intention for a non-xml format ?
In my mind, there is one example where non-xml format for sequences
would be very useful but I'm not satisfied with how it would actually
work in practice.
that is, I believe the most common actual production of XDM data
happens to be either plain text, or a single XML item (element,
document).
In both of those cases it would be really nice if the serialization
happened to be the 'standard' serialization for those without any kind
of wrapping at all,
(no ( ) or no <xdm:wrapper> .. etc)
That way if you just happened to produce a single XDM Item of type
element or text there'd be no extra baggage.
I think that would be really cool. But the only way I've thought of
to achieve that is to use a sequence delimited format with no start and
end markers.
My opinion is that if I'm going to have to parse "(" and "," I'd rather
be parsing "<wrapper> ... </wrapper>" at least I wouldn't
have to write a new (if even simple) parser and can simply read it as
XML. For example I would like to provide a 'sample implementation' of
the serialize and parser written in pure XQuery as an additional way of
describing the format besides prose.
But perhaps your thinking of a use case or design goal I have neglected.
David A. Lee
dlee@calldei.com
http://www.calldei.com
http://www.xmlsh.org
812-482-5224
Kurt Cagle wrote:
6fa681b10909201617h657b33bdk109e6b542e34be4a@mail.gmail.com"
type="cite">I'm not unaware of most of the implications of this
format, but I still think it's one that's worth thinking on.
For purposes of discussion, suppose that you arbitrarily split sequence
serialization from single-item serialization into non-XML formats
because I believe they are actually qualitatively different problems.
Referring only to the sequence serialization side of the problem here,
I think the question is whether XML sequence serialization and parsing
has to in fact be consumable by an XML parser. As I see it, you either
end up specifying some arbitrary set of privileged xml sequence tags:
<?xml version="1.0" encoding="UTF-8"?>
<xml:sequence xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xml:item value="foo" type="xs:string"/>
<xml:item value="5" type="xs:positiveInteger"/>
<xml:item
type="document"><bar><bat/></bar></xml:item>
<xml:item type="comment">foo</xml:item>
</xml:sequence>
or you work with a direct serialization as described earlier, possibly
with RDF encodings for type:
(<?xml version="1.0"
encoding="UTF-8"?>,"foo",5^positiveInteger,<bar><bat/></bar>,<!--
foo -->)
Non-native-xml items, such as binary classes invoked through extensions
in XQuery or XSLT, would be a more complex proposition, but otherwise I
don't really see where you'd have that much trouble with the notation.
It would require a modification of any XDM aware application to handle
the latter, but I don't necessarily see that as being that major an
issue at this stage.
I could see this approach mirroring the approach that RNG utilizes -
providing two equivalent representations, one in XML, the other as a
compact notation. The serializer in this case would work the way it
always does - you would describe the sequence serialization method and
possibly content type, and make a distinction between xsx - xml
serialization - and xsc - compact notion serialization.
Kurt Cagle
Managing Editor
http://xmlToday.org
On Sun, Sep 20, 2009 at 2:29 PM, Michael Kay
<mike@saxonica.com> wrote:
I'm going to ask what may be an obvious question, but
wouldn't it make sense for a serialization of a sequence to correspond
on the output to the serialization on the input? That is to say, if you
had a structure:
("foo",5,<bar><bat/></bar>,<!-- foo -->)
The main
disadvantage of such a format is that it uses non-XML markup
(parentheses and commas) which makes it difficult to parse using tools
that are specialized to handling XML markup, for example XSLT and
XQuery.
Also, it
doesn't solve the problem of retaining type annotations, for example
the difference between the integer 5 and the positiveInteger 5.
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