Re: [xml-dev] Epischema Article on XML.com

["Imsieke, Gerrit, le-tex" <gerrit.imsieke@le-tex.de>]

Hi Felix,

I remember your presentation -- 2010 was the first XML Prague conference 
that I attended!

Whether it's better to write a complete schema for the constrained base 
vocabulary from scratch, to use other schema customization methods, or 
to use another layer (Schematron, epischema) is a pragmatic question.

If I need a highly restricted HTML schema, I'll probably write one from 
scratch, as you did.

If you think of an EPUB editing tool that wants to enforce certain 
constraints on the use of headings, the content must still be valid 
against XHTML 1.1 (for EPUB 2) or to a variant of (X)HTML5 (for EPUB 3) 
in the first place. But you don't want to look into either of the base 
schemas in order to find out which detailed models need tweaking. If 
there's a constraint layer that can be added on top of either base 
schema, you'd certainly prefer this.

Of course there are other customization methods than adding Schematron 
or epischema on top. But base schemas often don't provide redefinable 
content models at the desired granularity, or the schema language 
doesn't offer context-dependent (co-occurrence) constraints at all.

Gerrit


On 01.05.17 09:55, Felix Sasaki wrote:
> Hi Gerrit,
>
> I think this approach is very useful. I did something similar to have 
> a special purpose, XHTML based editing and publication workflow for 
> multilingual document creation, see
> http://archive.xmlprague.cz/2010/presentations/Felix_Sasaki_How_to_avoid_suffering_from_markup_A_project_report_about_the_virtue_of_hiding_XML.pdf
> and the paper at
> http://archive.xmlprague.cz/2010/files/XMLPrague_2010_Proceedings.pdf#page=123
>
> Using RELAX NG to constraint (X)HTML could fill a gap that there is in 
> the current Web content authoring technology stack.
>
> - Felix
>
>
> 2017-05-01 9:29 GMT+02:00 Imsieke, Gerrit, le-tex 
> <gerrit.imsieke@le-tex.de <mailto:gerrit.imsieke@le-tex.de>>:
>
>     Adding a second Relax NG schema in the way you'd add a Schematron
>     schema is an (in my view) nice approach to constraining a base schema.
>     It is orthogonal like Schematron: You don't need to know or modify
>     the building blocks that the base schema provides.
>     Unlike Schematron rules, the additional Relax NG schema may be used
>     by XML editors for content completion.
>     Those of you who listened to this year's XML Prague presentation
>     [1,2] about adding a Docbook-like grammar to TEI divs already know
>     the concept. In a recent article on XML.com [3], I've applied this
>     approach to HTML, using the HTML-first publishing workflow that Dave
>     Cramer described [4] as an example.
>     I've called this approach, that to my surprise (and admittedly
>     modest knowledge) was hitherto unheard of, "epischema" (epi = on top
>     of).
>     Please note that I'm not advocating against the use of Schematron;
>     on the contrary. It's just that there's an alternative way to
>     express a certain class of constraints (grammatical ones), and this
>     alternative provides specific, context-dependent content completion
>     suggestions as a side effect.
>     Looking forward to receiving your comments.
>
>     -Gerrit
>
>     [1]
>     http://archive.xmlprague.cz/2017/files/presentations/epischema/index.html
>     <http://archive.xmlprague.cz/2017/files/presentations/epischema/index.html>
>     [2]
>     https://youtu.be/BOHtdnQEokQ?list=PLQpqh98e9RgUcEmbXmI6RolisQaIRw9dm
>     <https://youtu.be/BOHtdnQEokQ?list=PLQpqh98e9RgUcEmbXmI6RolisQaIRw9dm>
>     [3] https://www.xml.com/articles/2017/04/29/epischemas/
>     <https://www.xml.com/articles/2017/04/29/epischemas/>
>     [4]
>     https://www.xml.com/articles/2017/02/20/beyond-xml-making-books-html/ <https://www.xml.com/articles/2017/02/20/beyond-xml-making-books-html/>
>
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Gerrit Imsieke
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