> To say that attribute
> "bar" is optional, we could write:
> <bar eg:node="attribute" eg:occurs="?"/>
That's clean, but it doesn't really buy you anything over using the
eg:attribute that you've imported from RNG.
<eg:attribute name="bar" eg:occurs="?"/>
assuming you've extended occurs to apply to RNG elements as well.
> The second option would lead to more complex stuff such as:
>
> <foo bar="occurs=?, type=xsd:integer"/>
Yuck!
I think attributes are the real challenge for an example-based syntax.
While I was designing TREX, I played with such syntaxes (based on my XSLT
experience with literal result elements), but I failed to find an approach
to handling attributes that I liked.
I think a bit more brainstorming is required. One possibility:
<foo optional:bar="xsd:integer" required:baz="xsd:integer"/>
where optional, required are bound to special Examplotron-defined namespace
URIs. Would only work for local attributes, but I suspect local attributes
are the 80% case.
Another is to use a syntax that is not legal XML:
<foo bar="xsd:integer"? />
You could have a simple little pretransform to turn that into something
that was legal XML before doing the XSLT transform into RNG.
> <foo eg:ref="foo-content"/>
Having an attribute on a literal element that refers to a definition for
the content is a nice idea, but I'm not sure whether the similarity with
the <eg:ref/> element that you will have imported from the RNG namespace is
a help or a hindrance.
James
