config language

Greg Watson gwatson at lanl.gov
Tue May 20 09:57:08 CEST 2003


Hi Bob,

The config language does lend itself to XML, (and it was my first 
thought when Ron suggested a new languge) but I would recommend 
against it for a couple of reasons. The first is that the language 
needs to serve the dual purpose of specifying *and documenting* a 
particular configuration. XML is great for the former, but is almost 
impossible to read easily, particularly for people not used to 
working with it. Sure, you could then add something that converts the 
XML into a more readable document, but then what is a simple idea is 
now becoming very complicated. Secondly, and more importantly, is 
that it would mean that LB relies on the existence of an extremely 
complex external component, that is out of the control of the LB 
community (be it pyRXP, libXML, or whatever). Arguably this is 
already the case, since the configuration process uses python, but if 
we adopt a new configuration language then the parser can be included 
as part of the distribution - making it effectively self-contained. 
So in my view the limitations of using XML outweigh any advantages 
that might be obtained.

Regards,

Greg

At 9:24 AM -0400 20/5/03, Bob Drzyzgula wrote:
>On Tue, May 20, 2003 at 06:49:15AM -0600, ron minnich wrote:
>>
>>  On Tue, 20 May 2003, Mark Wilkinson wrote:
>>
>>  > Greg, what you've suggested looks to lend itself towards an XML type
>>  > markup.
>>
>>  Thanks for the suggestions and looking at the idea, but we're not going
>>  XML. Sorry, but we've got a real bias here against using text markup
>>  languages for other purposes.
>>
>>  Besides, Greg language is pretty, and the xml example is in my opionion
>>  kind of ugly ...
>>
>>  Other than that, however, sounds like you think Greg's idea is ok?
>>
>>  ron
>
>Ron,
>
>Given that you just bemoaned the work neccessary to build
>a C-based parser for a new language, one would think that
>you would be interested in a solution wherein the parser
>comes pretty much for free. With an XML-based config file,
>you can have a correct, validating parser implemented in
>an afternoon. With some thought put into defaults, the
>translation of the existing config files into XML could be
>automated with a small amount of effort, and config file
>editors that do not allow the creation of invalid config
>files could easily be constructed.
>
>PyRXP will vacuum up an XML document into a native Python
>data structure, and validate the document against a DTD
>if you have one: http://www.reportlab.com/xml/pyrxp.html
>It's fast, GPL'd, and brain-dead easy to use.
>
>--Bob
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