On 11/3/06, Frank Budinsky <[EMAIL PROTECTED]> wrote:
In the Tuscany Java implementation we expose CDATA as sequence entries
(like mixed text) with a special "CDATA" property (we handle comments in a
similar way). SDO doesn't define a special property for CDATA, so this is
an implementation-specific feature. I'm not sure, long term, what should
be the best (proper) way to do this.
Frank.
"Simon Laws" <[EMAIL PROTECTED]> wrote on 11/03/2006 09:41:25 AM:
> On 10/26/06, Simon Laws <[EMAIL PROTECTED]> wrote:
> >
> > This is primarily a C++ question but I guess could apply to Java also.
I'm
> > trying to read a document into C++ SDO that contains a CDATA section.
The
> > corresponding CDATA doesn't make its way into the resulting SDO. I put
the
> > C++ SDO implementation in the debugger and found the reason why:
> >
> > sax2parser.cpp
> >
> > void sdo_cdataBlock(void *ctx, const xmlChar *value, int len)
> > {
> > }
> >
> > So the callback exists, gets called with the correct data during the
> > parse, i.e. LibXML2 is doing the right thing, but the callback is
ignored.
> > Is there a good reason for this? I did a quick search of the C++ and
Java
> > specs and they don't appear to discuss CDATA specifically. Can someone
> > comment on whether the Java implementation handles CDATA successfully?
> >
> > Logically, from an SDO point of view, there is probably no need to
treat
> > CDATA specially as the SDO model dictates precisely the difference
between
> > data and structure. We may find that to make the XML DAS function work
we
> > have to know that a property potentially contains markup but I'd have
to
> > look closely at how the C++ SDO implementation of the XML DAS function
> > streams out SDOs to XML when requested to do so.
> >
> > If CDATA hasn't been omitted for a good reason I'll come up with a
> > proposal for C++ SDO.
> >
> > Regards
> >
> > Simon
>
>
>
> I didn't get any response to this. Here are my further thoughts..
>
> There are a number of options for representing CDATA in SDO, for example
>
> 1) Duplicate the CDATA string as is, including the "<![CDATA[" and "]]>"
> markers, to the appropriate property in the data object hiearchy
> 2) Duplicate the CDATA string excluding the "<![CDATA[" and "]]>"
markers
> and instigate a special flag to indicate that CDATA is present.
>
> CDATA is the specific concern of XML, i.e. the chracter entities that
CDATA
> protects an XML parser from are of no
> concern to SDO because SDO is not intended to be tied directly to XML.
So
> given the example options above we
> either expose the specifics of XML to the SDO core 2) or to the SDO user
1).
>
> Neither are particularly attractive.
>
> 1) appears to be the simplest approach to implement because it provides
a
> mechanism for the user to read, and
> create CDATA without having to provide much special support in SDO. 2)
is
> more involved particularly because
> CDATA can appear mixed in with other text strings and so a sequence may
need
> to be used to represent properties
> that have a mixture of text and CDATA marking those sequences entries
that
> are CDATA.
>
> 1) does require changes (at least in C++ SDO) because XML parsers tend
to be
> too helpful in this case for
> processing CDATA. XML parsers, libxml2 in particular, recognize the
> "<![CDATA[" and "]]>" sequence as a special
> indicator and throw it away returning just the text it includes. We
would
> have to reintroduce it and store it in
> the parameter value in question. The C++ SDO implementation uses a lot
of
> XML string handling before the parameter
> value is actually stored which URL encodes parts of the CDATA markers so
> this would have to be fixed. When writing out the CDATA strings any
string
> typed properties would have to be scanned for the markers so that the
> appropriate libxml2 functions can be called to get the CDATA sections in
the
> right place.
>
> I have a test implementation of 1). If this is the way we want to go I
would
> have to do more work to thread CDATA handling through the xml strings
that
> are used to set parameters. Happy to do this but would like to discuss
> first.
>
> Thoughts (particularly on what Java SDO does with CDATA)?
>
> Simon
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Ok, thanks for that Frank. It would be nice for us to do it in the same
way so even though it is not in the SDO spec the implementations are
similar. A question, how do you set a sequence entry to indicate that it
holds CDATA. Is this a flag that is exposed on the sequence API. I'm not
really familiar with the Java SDO code base. Can you give me a class name to
go look at?
Simon
