[Freegis-list] GML

[Allan Doyle]

Lakshman Gollamudi wrote:
> 
> Hi All,
> I am a newbie to GIS. I have been looking into GML and am evaluating a
> possibility to use GML-SVG for displaying maps. This is purely a study and I
> intend to come out with an understanding of what is the best way to render
> maps on a browser.
> The scneario of my exercise would be something like this:
> A user can come to the website and ask for a map. I need to pick the
> appropriate map from the set which is essentially in GML format, convert it
> to SVG on the fly and then push the SVG to the browser. For now, I am not
> including any user interaction on the map like selectig a point etc.
> I have the following questions:
> 1. Why do we need a WFS? I have not been able to understand the concept of
> WFS. Can I not use a simple webserver?

A Webserver would let you get predefined chunks of GML. I.e. you are
still in a file-based world. A WFS lets you input a query (Get me the
features whose occupancy property is greater than 3 within this polygon)
and get back GML. If you also implement transactions in the WFS you can
upload individual features or groups of them, or delete or modify
existing ones.

> 2. Do I have to buy a tool that converts GML to SVG on the fly?

That depends on what you want to do. At this point, GML to SVG seems to
be implemented via either building a SAX or DOM based GML reader that
then emits SVG, or by building XSLT style sheets. You can find some of
the latter at www.gmlcentral.com/tiger

> Please pardon me if the questions are very trivial.

No, this is new stuff, there are bound to be many questions until enough
information exists for people to look at.

> Regards
> Lakshman
> 

	Allan

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Allan Doyle                         http://www.intl-interfaces.com
adoyle at intl-interfaces.com