XML file formats .... was: Re: gEDA-user: Some footprints I tried to create

[Stuart Brorson <sdb@xxxxxxxxxx>]

> Sounds like a job for XML :-) .  Really, I don't see the big deal. If you 
> would like am XML format, write a parser that will take the current format 
> and generate XML to and from that. This could be located in the File->Export 
> / File->Import menu (or something like that). Now you get your XML and others 
> can keep what they currently use.

I don't want to go into great detail about the argument against XML
again.  I'll observe that we have this same debate about XML file
formats every two or three years.  I think it has to do with how long
it takes us to lose our institutional memory due to churn on the
mailing list.

Maybe I'll write an item for the FAQ about why we don't junk the file
format in favor of XML.  In short, the reasons against XML are:

*  We already have a fixed, well documented, ASCII file format
already.  It's over 8 years old, well used and well tested.

*  We already have a parser for our file format already.  Its
lightweight & thoroughly debugged.

*  There are lots of legacy designs using the file format out there
already.  People would scream if we switched file formats since their
old designs would become obsolete.  And supporting two file formats --
old and new -- would be a major PITA.

*  As somebody already observed, XML files are bloated pigs.  The gEDA
file format is light & well adapted to its purpose.

*  One purported benefit for XML files is that there are lots of
open-source parsers for them available, making integration into
libgeda trivial.  That's the theory, but in reality the job
of a parser is to parse the input, and then stick it into
datastructures suitable for use with the rest of gschem's code.  An
open-source parser does about 1/3 of the job we need (i.e. reading the
file & creating some kind of parse tree).  The rest of the job
involves putting the stuff in the parse tree into libgeda's data
structures.  That's lots of work.  Therefore, the purported advantage
of the freely-available XML parser is a chimera.  Yes, it may be of
interest for a new program written from the ground up, but not for an
existing program like gEDA.

*  Our developer time is better used on implementing new features like
backannotation.  Using developer time on porting our file format to
XML is a sideways move which doesn't provide the end user any more
utility, but soaks up valuable developer time.

*  The other benefit of XML is that it is more-or-less human
readable.  I'll grant that this is a valid assertion.  Our current
file format is not readable by a human who has never read the
documentation.  However, our current file format *is* ASCII, and is
completely documented, so an essential reason for readability -- the
ability to write scripts against the file -- is already taken care
of.  Also, a human can certainly read the file format once he has
taken the time to RTFM.  Human readability -- without knowing the file
format -- is a "nice to have" which isn't high on my priority list.


These are just my opinions, of course.

Finally, if you really, really want to play with gschem files in XML,
you can grab a pair of .sch <-> XML utilities I wrote 4 years ago
here:

http://www.brorson.com/gEDA/gschem/

If you really want XML schematic files, have fun with those little
utilities!

Stuart


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