[e-lang] XML support in E

[Kevin Reid]

On Oct 26, 2009, at 13:08, Thomas Leonard wrote:

> Could someone give some simple examples showing how to read and write
> XML using E?
>
> The XMLQuasiParser looks reasonable, but says it is deprecated in  
> favour
> of using Terms. I can build Terms manually, but I can't see how to  
> turn
> serialised XML into a Term, or a Term into serialised XML.
>
> I found this, but it doesn't say which methods to call:
>
> http://www.erights.org/data/terml/embeddings.html
>
> There's also Term.updoc in the source, which shows how to convert a  
> sml
> DOM to a term, but not the other way around. Also, sml doesn't support
> all of XML, e.g.
>
> ? sml`<foo/>`
> # problem: Failed: syntax error: expected '>' but got '/' at 4

There is no E-styled XML library built into E; this is certainly  
something which ought to be addressed.

Such a library should of course use immutable trees (vs. e.g. DOM  
which is mutable) and have quasiliteral/pattern support for users.


E-on-JavaScript's Updoc-to-HTML component is an example of XML  
manipulation in E: it uses the Java DOM libraries (and, when a real E  
XML library exists, should be converted to use it).
   http://wiki.erights.org/wiki/E-on-JavaScript


There are two different approaches which could be used for an E XML  
library: one is to use the Term-tree objects, and merely write an  
xml__quasiParser which allows one to use the XML-in-TermL embedding,  
as well as facilities for reading/writing XML documents. The other is  
to have a distinct object type for XML tree nodes; this has the  
advantage that its methods can be optimized for the needs of XML  
applications, and its __printOn would show XML rather than TermL.

Parsing and printing could be handled for starters by using Java's  
builtin XML facilities; I'm not sure exactly how much could be reused  
vs. reimplented.

Questions:

   * Would you be interested in working on the project of an XML library
     for E?

   * If I were to work on it, would you use it and give feedback?

-- 
Kevin Reid                                  <http://switchb.org/kpreid/>