Re: [lmi] an xml schema for (single|multiple)_cell_document file XML format

[Vadim Zeitlin]

On Mon, 27 Feb 2012 15:34:30 +0000 Greg Chicares <address@hidden> wrote:

GC> On 2010-08-09 16:28Z, Vadim Zeitlin wrote:
GC> > On Sun, 08 Aug 2010 16:28:55 +0000 Greg Chicares <address@hidden> wrote:
GC> > 
GC> > GC> On 2007-12-27 12:43Z, Evgeniy Tarassov wrote:
GC> > GC> > 
GC> > GC> > The newer version of XML Schema files for cns/ill files could be 
downloaded
GC> > GC> > from lmi project download area at savannah:
GC> > GC> > | 
http://download.savannah.nongnu.org/releases/lmi/cell_document.tar.bz2
GC> > GC> 
GC> > GC> If we were doing this all over today, would XML Schema still be a 
good choice,
GC> > GC> or is something else like RELAX NG or Schematron clearly better now?
GC> > 
GC> >  I'm not aware of any dramatic changes in the XML validation area since 
the
GC> > last 3 years so I'd be tempted to say no, i.e. that XML Schema still
GC> > remains a decent choice because even though RELAX NG has its advantages
GC> > over it (notably relative simplicity) it's still less standard/supported 
by
GC> > various tools than it. As for Schematron, I believe it's mostly used in
GC> > addition to either XML Schema or RELAX NG and not solely on its own 
anyhow.
GC> > 
GC> >  I could look more into recent developments in this area but, frankly, I
GC> > doubt that we're going to find any earth shattering revelations. IMHO it
GC> > would make sense to stick with XML Schema even if subjectively I like 
RELAX
GC> > NG "compact syntax" (http://en.wikipedia.org/wiki/RELAX_NG#Compact_syntax)
GC> > a lot.
GC> 
GC> I wonder whether we should reconsider that, and perhaps use RELAX NG
GC> instead.

 I've briefly looked at this again and I found that the difference in
degree of support in the various tools between XML Schema and RELAX NG has,
if anything, become even greater in the last couple of years. However RELAX
NG is still considered to be a better choice for XML validation (only) and
so this could be explained by the fact that there is simply not much else
to do with it, while XML Schema is used for many things (data bindings;
serialization; code generation; ...) other than validation because it's, in
fact, better suited for them than for validation.

 I also found Trang (http://www.thaiopensource.com/relaxng/trang.html)
which can be used to translate RELAX NG to XML Schema and apparently quite
a few people use it successfully with XML Schema tools by writing the
schema in RELAX NG and then just converting it to XML Schema automatically.
So the following strategy seems safe enough: use RELAX NG for the schema
but ensure (by running Trang on it periodically) that it can be converted
to XML Schema if needed. Like this we get the benefit of nicer input
language without being locked into using it for ever.

 BTW, I also found mentions of some problems with RELAX NG validation in
libxml2 (and hence xmllint). They were relatively old so perhaps things
have improved since then but, just in case it can be useful, there is also
a tool specifically for validating with RELAX NG at the same site called
Jing (http://www.thaiopensource.com/relaxng/jing.html) that could be used
too.


GC> For now, only '.cns' and '.ill' files need be covered. Obsolete historical
GC> versions needn't be supported; we'd want schema support only for current
GC> and future versions.

 We can try to produce a RELAX NG schema for them to see how it goes.
Should we?
VZ