[mapserver-users] XML mapfile?

Wed May 22 20:08:45 EDT 2002

I haven't made much contribution to this list but I feel that I want to say
something now.  I thnk that XML is a very good direction to go for the
following reasons:

1. As Vic mentions the XML document instance can be parsed against a DTD to
find out it if is valid and well formed.  This saves editing problems. 

2. There are many editing tools that would make editing the XML document
very easy and some actually properly parse the XML documents against a DTD!
;--)

3. I would go one step further and suggest that an XSD or (even easier to
develop) RELAXNG be developed instead of a DTD to for the map file.  Either
of these two formats allow content checking during the parsing process.
Something that DTDs aren't very good at doing.  

For instance, the RELAXNG or XSD can be used to check content during the
parsing process:

	a) the STATUS can be a selection from "on", "default" etc.

	b) the COLOR can be three numbers separated by spaces

	c) the UNITS can be a selection ftom "kilometers", "miles", "feet",
etc

4. As Vic mentions the XSD or RELAXNG is almost self documenting, especially
if there are a lot of comments throughout the XSD or RELAXNG document.

5. The OpenGIS consortium is using XML for the WMS, WMC, WFS etc.  If these
use DTD, XSD or RELAXNG then mapserver could adopt these for the map file
and most of the work would be done.

I fully support using the XML technologies for mapserver.  They have made my
life much easier.

John

> -----Original Message-----
> From:	Ryan, Adam [SMTP:ARyan at co.linn.or.us]
> Sent:	Thursday, 23 May 2002 07:11
> To:	mapserver-users at lists.gis.umn.edu
> Subject:	RE: [mapserver-users] XML mapfile?
> 
> 
> Don't know about xml mapfiles but I use small xml documents to populate
> drop
> down boxes depending on what map file the template is using.  I have to
> maintain more files but they're small and simple and it's an easy way to
> get
> at external data.
> 
> Adam Ryan
> Linn County GIS
> 
> -----Original Message-----
> From: Steve Lime [mailto:steve.lime at dnr.state.mn.us]
> Sent: Wednesday, May 22, 2002 11:32 AM
> To: morissette at dmsolutions.ca; gis_consultant at hotmail.com
> Cc: mapserver-users at lists.gis.umn.edu
> Subject: Re: [mapserver-users] XML mapfile?
> 
> 
> Ok, you're a whiner. <g>
> 
> This is being looked into. There are other competing priorities at the
> moment so it's down
> the list a bit right now. My plan would be to support both native and
> XML-based configuration
> in the short term until some of the performance issues could be dealt
> with. One could actually
> make MapServer read XML with just a few tweaks of the lexer, and since
> you wouldn't validate
> at that point anyway...
> 
> I'd like to see the conversation continue, perhaps off list with a
> smaller group. Some practical
> demonstrations of the benefits of an XML-based config file might also
> help those of us not 
> experienced with XML see the light.
> 
> Steve
> 
> Stephen Lime
> Data & Applications Manager
> 
> Minnesota DNR
> 500 Lafayette Road
> St. Paul, MN 55155
> 651-297-2937
> 
> >>> "C F" <gis_consultant at hotmail.com> 05/22/02 10:51AM >>>
> I hear you on the performance concerns.  However, I think we could get
> 
> around that by serializing the XML DOM object into a file (that's how
> ArcIMS 
> does it.... which probably hurts my case more than anything).  Then the
> only 
> time the XML file would be parsed is in the first request after a
> change to 
> it is made (done by using file's timestamps).  Who knows, it might even
> be 
> fast than the current implementation.  I don't really know if that's
> true as 
> I have not actually used serialized DOM files in my own apps... but it
> makes 
> sense to me that it could possibly alleviate your performance
> concerns.
> Now, assuming that performance wasn't an issue, I still hear concerns
> about 
> simplicity.  In raw text-edit mode, there's nothing that can be done
> about 
> that.  I consider it a very minor difference... but that's just a
> matter of 
> taste and there will never be a consensus on that.  All I can say about
> that 
> is that XML would make it tremendously easier for people to write
> mapfile 
> generation/editing tools.... also for people writing tools to batch
> update 
> their mapfiles, etc.  In other words, with maybe the very minor
> exception of 
> manual text editing, it would make them much easier to handle.... again
> a 
> maybe matter of taste :)
> MapScript is a solution... but may not be a solution for everyone if
> they 
> want to build a more of a single, cross-platform solution with minimum
> 
> modification and customization to the servers involved.  Also, the fact
> that 
> we'd gain access to this important mapfile information without the need
> for 
> "programming" would be nice.  I envision this would be set up in much
> the 
> same way it is now, only with XSLT templates replacing the current form
> of 
> templates.
> 
> Well those are my thoughts.... but I haven't really received any
> positive 
> feedback since my original post so it looks I'm all alone :)  People
> seem to 
> be comfortable with the current format.  Or maybe I'm just looking at
> it for 
> use in different uses than it has traditionally been used for.  I think
> 
> everybody that's worked on it has done an *awesome* job.  I think the 
> product is great, just call me a whiner if you'd like :)  Paul Ramsey's
> idea 
> of out we could have it both ways is something I might do for myself
> anyway. 
>   If there is ever enough interest in it maybe that's somewhere I can 
> contribute to the project.
> 
> 
> 
> >From: Daniel Morissette <morissette at dmsolutions.ca>
> >To: C F <gis_consultant at hotmail.com>
> >CC: mapserver-users at lists.gis.umn.edu 
> >Subject: Re: [mapserver-users] XML mapfile?
> >Date: Wed, 22 May 2002 08:19:31 -0400
> >
> >I think that Steve has been considering a switch to XML eventually,
> but
> >I don't think there is any formal plan.
> >
> >I agree that XML might give more flexibility to the user by allowing
> him
> >to read the mapfile from external tools, but it would be at the cost
> of
> >performance (i.e. speed) when parsing the mapfile for every request.
> >Combine this loss of performance with the fact that XML would be
> harder
> >to edit manually than the current format, and you know where I stand
> >personally.
> >
> >I'm not saying that if we were redesigning from scratch I wouldn't
> >consider XML (we use it a lot in other apps), but since we've already
> >got a very good (fast and simple) mapfile format then I won't be the
> one
> >initiating a switch to XML mapfiles.
> >
> >Note that MapScript already gives you access to almost every piece of
> >information from the mapfile, so when the CGI cannot do what you need
> >then the logic path is to switch to MapScript, and then sky is the
> >limit.
> >
> >My 0.02$
> >--
> >------------------------------------------------------------
> >  Daniel Morissette               morissette at dmsolutions.ca 
> >  DM Solutions Group              http://www.dmsolutions.ca/ 
> >------------------------------------------------------------
> >   Don't put for tomorrow what you can do today, because if
> >       you enjoy it today you can do it again tomorrow.
> 
> 
> 
> 
> 
> 
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