[NTG-context] TeX in \xmlsetentity and DTDs in DOCTYPEs

Kate F kate at elide.org
Mon Jan 18 21:49:34 CET 2016


On 18 January 2016 at 19:13, Hans Hagen <pragma at wxs.nl> wrote:
> On 1/18/2016 5:22 PM, Kate F wrote:
>>
>> On 18 January 2016 at 13:30, Thomas A. Schmitz
>> <thomas.schmitz at uni-bonn.de> wrote:
>>>
>>> On 01/17/2016 07:24 PM, Hans Hagen wrote:
>>>>
>>>>
>>>> it should work in the in beta now
>>>
>>>
>>>
>>> Hi Hans,
>>>
>>> now I have a problem :-) What should take precedence if an entity is both
>>> defined in the dtd and as a \xmltexentity? The way I see it, the latter:
>>> e.g., in the DTD, I might declare something for use in a browser but
>>> require
>>> a different solution when typesetting with ConTeXt. The latest and
>>> greatest
>>> now takes my DTD definitions instead of the \xmltexentities, which did
>>> not
>>> happen before. Is that an unwanted side effect or the new default?
>>>
>>
>> Ah, there's a bug:
>>
>>      <!ENTITY i.opt "<option>-i</option>">
>>
>> This should produce an <option> node in the DOM tree, just as if you'd
>> typed that out where the entity is used. Currently ConTeXt takes that
>> as literal text, as if you'd typed "<option>-i<option/>"
>>
>> Often I wish XML weren't so complex...
>
>
> are you sure? i've never seen that
>
> Hans

Yep!

These are called "internal parsed entities". "Parsed" requires that
any tags *inside* the entity must be balanced, unlike in SGML
entities.

Sorry I can't find a clear explanation in the XML spec; it's a pretty
confusing document.
But here's some random person's slide illustrating an example:
http://images.slideplayer.com/23/6622270/slides/slide_47.jpg

libxml2 deals with these correctly, which is what I've been using
(xsltproc and friends) for my documents which use them. I generally
trust libxml2 to get things right.

I use these entities to centralise often-repeated fragments between
documents, kind of like how you might use a primitive macro in TeX.

So for example in one external DTD I have some general things:

    <!ENTITY macro.arg  "<replaceable>macro</replaceable>">
    <!ENTITY equal.lit      "<literal>=</literal>">

And then in one specific document's internal entities, something which
uses them:

        <!ENTITY D2.opt
"<option>-D</option>&macro.arg;&equal.lit;<replaceable>defn</replaceable>">

Then if I change my mind about how I want to mark up "=", for example,
I only have one place to change it. This makes life with XML a little
bit less painful.

-- 
Kate


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