Re: TeX in \xmlsetentity and DTDs in DOCTYPEs

[Kate F <kate@elide.org>]

On 18 January 2016 at 21:16, Hans Hagen <pragma@wxs.nl> wrote:
> On 1/18/2016 9:49 PM, Kate F wrote:
>>
>> On 18 January 2016 at 19:13, Hans Hagen <pragma@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@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 "&lt;option&gt;-i&lt;option/&gt;"
>>>>
>>>> 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.
>
>
> well, i've learned not to trust all these docs on the web too much and
> applications can do what they want (and thereby even influence standards)
>
> xml pocket reference:
>
> - parsed entity: replacement text that can be referenced
>
>   internal: literal string to be injected (then the example
>             shows only text and entities
>
> in your example you use a (decimal) character entity ... the link you give
> says that you cannot use & and % as part of the entities value so that would
> mean your example is wrong
>

Indeed I did not mean that somebody's presentation slides are normative.

This is normative for XML 1.0:
https://www.w3.org/TR/1998/REC-xml-19980210#wf-entities

Which has the following productions:

    extParsedEnt ::= TextDecl? content
    content ::= (element | CharData | Reference | CDSect | PI | Comment)*

So you can see that both elements (by "element") and entity references
(by "Reference") are permitted in the grammar. The latter includes:

    Reference ::= EntityRef | CharRef
    EntityRef::='&' Name ';'

Per this, all my examples are correct.

O'Reilly XML in a Nutshell has an example:
http://docstore.mik.ua/orelly/xml/xmlnut/ch03_04.htm


> of course we can consider an option to parse the entity as xml
>
> (we can consider < as a trigger for parsing thereby kin dof automatically
> adapting)
>

I do not think this is a good idea - per the XML spec, these entities
should always be taken as well-formed fragments of XML. So treating
them otherwise would be incorrect.

Thanks,

-- 
Kate
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