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| Re: multivalued attributes [message #45012 is a reply to message #44900] |
Sun, 04 May 2008 01:32  |
 Paul Elder
Messages: 849
Registered: July 2009 |
Senior Member |
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Felix:
JET (XPath, too) has problems with multi-valued attributes. XML doesn't
really have the concept (apart from the lame semantic used in types like
IDREF, were multiple values are separated by some special char in a single
attribute value).
I have though about have some way to annotate a model element with new
model elements (just as you can annotate a model element with a new
attribute via c:set). But, I haven't got around to doing it. If we play
thought experiments for a second, it would be something like the current
c:addElement (which only works if the underlying meta-model allows:
<%-- assuming $r some model element --%>
<c:addAnnotationElement select="$r" name="foo" var="foo"/>
<c:set select="$foo" name="name">foo 1</c:set>
<c:addAnnotationElement select="$r" name="foo" var="foo"/>
<c:set select="$foo" name="name">foo 2</c:set>
Then, you could do:
<c:iterate select="$r/foo" var="foo">
<c:get select="$foo/@name"/>
</c:iterate>
and expect results like:
foo 1
foo 2
I also have some ideas about making multivalued attributes addressable by
XPath. Again, I haven't had time yet, but it might work something like:
<c:get select="$r/@aMVAttr[1]"/>
<c:get select="$r/@aMVAttr[2]"/>
...
Anyone familiar with XPath in the XML context would assert that the first
expression is equivalent to $r/@aMVAttr, and the second would never return
a result. But, if multivalued attributes existed (as they do in EMF
models), then I think this would be a reasonable way to index them.
Anyhow, if I get around supporting that, then maybe we could have c:set
extended to do something like:
<c:set select="$r" name="aMVAttr" index="2">a value</c:set>
or maybe
<c:set select="$r" name="aMVAttr" index="atEnd">a value</c:set>
If you think this may be worthwhile, please submit a bugzilla enhancement.
I remember things better if they show up in bugzilla:-) Here's a
'shortcut' to submit one:
https://bugs.eclipse.org/bugs/enter_bug.cgi?product=M2T& version=unspecified&component=Jet&rep_platform=PC&am p;op_sys=Windows%20XP&priority=P3&bug_severity=enhan cement&bug_status=NEW&bug_file_loc=http%3A%2F%2F& ;short_desc=&comment=&commentprivacy=0&keywords= &dependson=&blocked=&maketemplate=Remember%20val ues%20as%20bookmarkable%20template&form_name=enter_bug&a mp;assigned_to=m2t.jet-inbox%40eclipse.org
Paul
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