[postgis-users] GML vs SVG {-5.2}

[Paul Ramsey]

They are thinking "aha, GIS data transport is standardizing on GML, so 
if I work out a nifty transformation tool based on XSLT, I can transform 
data from any source at all into attractive SVG".  This is what Galdos 
(www.galdos.com) makes their living doing (among other things).

GML is a "Geographic" markup language, it is specifically designed for 
encoding GIS style data. It has no information about stylings or 
display, just about content. SVG is about display, color, style. Think 
of GML as being XML and SVG being more like HTML, as an analogy.

Sean Montague wrote:

> This is where I am getting confused.  I read in places that people
> are using xslt to display GML as SVG.  Are these people not reading
> the data from a database?  Storing the data as GML and displaying it
> as SVG.  Which if this is a case, then to read directly from a
> database like postgreSQL and PostGIS, GML is a wasted step if the
> ultimate format is SVG.  What I'd really like is a caparison of GML
> vs SVG, if it is appropriate.  SVG is very powerful and I know it
> well.  I've written apps that query a MySQL database and have
> customized some tools.   I'm just trying to figure out if I should
> learn GML.  Is there something about GML that is an advantage over
> SVG?  Thanks.
> 
> 
>>>> pramsey at refractions.net 04/07/04 10:08AM >>>
> 
> Sean Montague wrote:
> 
>> I have made many a map with SVG, but I'm new to PostGIS.  So new in
>>  fact that I haven't even installed it yet.  I've been using MySQL,
>>  but have come to the conclusion that postgreSQL is the way to go. 
>> So, for those of you familiar with both SVG and GML, can you
>> explain the relationship between the two, it seems they are not
>> mutually exclusive, and why wouldn't I write directly to SVG if a
>> map ends up in SVG anyway?  I'm trying to sort through all this to
>> determine the direction I should go in.  Thanks.
> 
> 
> If you are determined to write out SVG then certainly GML gives you 
> nothing in terms of advantage. If you are building a more generic 
> infrastructure, then a WFS (web feature server that serves GML) on
> top of your database can provide a nice generic API to your
> underlying data.
> 


-- 
       __
      /
      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
      | Phone: (250) 885-0632
      \_