[mapserver-users] mapserver architecture for multi-websites o n several machines

[Hockaday, John]

Hi Claudia,

I was hoping that someone with more experience with this type of subject
would answer your question but it seems that they haven't so I will give you
the little knowledge that I have on the subject.  Hopefully, lots of people
will get annoyed with the errors in this e-mail that I am proposing and they
will correct me for your benefit.  I for one am very interested in the
outcomes of your project as I will have to look into something similar soon.

The Open GIS came up with a standard for accessing data across the web.  (I
think that the OpenIGS is called something different now but I'm not sure.)
One of the commands is something like getimage().  I believe that mapserver
version 3.5 has the ability to handle Open GIS capabilities.  I seem to
remember earlier versions having the getimage() command but I'm not sure
about that either.

You could use the getimage() command to each of your mapservers and they
should return an image.  You could then build these images on top of each
other, if they are transparent, to make a final map.  GD can do this if
mapserver doesn't already have a command to do it.  You may have to make
more that one call to each map server as the order of the layers may be
important to your final map.

I think that there is a similar OpenGIS command to get information about a
layer from a remote map server.  It may be something like getinfo().  This
is probably a more simpler command as it may only need information from one
mapserver.

I would *strongly* recommend that you use the OpenGIS standard as a lot of
work has gone into this standard and you will greatly benefit from their
detailed efforts.  I worked on a system of connecting to many map producing
servers a long time ago and it was full of problems therefore, we stopped
doing it.  Since then, the OpenGIS has addressed those problems in their
work.

Good luck and please keep this list aware of what you are doing.  I want to
build on your work if you don't mind me "borrowing" your intellectual
property and code.   ;--)

John

> -----Original Message-----
> From:	Claude Philipona [SMTP:claude.philipona at camptocamp.com]
> Sent:	Friday, July 13, 2001 8:38 PM
> To:	mapserver-users at lists.gis.umn.edu
> Subject:	[mapserver-users] mapserver architecture for multi-websites
> on several machines
> 
> We are starting a project using Mapserver (PHP/MapScript) for building a
> cartographic server which could be used by different client web-sites on
> different machines. The server will propose a large set of raster map from
> 1:25'000 to 1:1'000'000. The client web-sites will be able to use the
> central
> mapserver to interactivly geocode any kind of information (points, lines,
> surfaces) using an applet and to visualize and to navigate thru the
> obtained
> geocoded objects.
> 
> Each site using Mapserver is totally independent should be able to
> integrate the
> map directly (no frames).In this configuration we don't have a web borwser
> making
> direct request to MapServer, but rather the web server machines would have
> to
> make the cartogrphic request to the mapserver machine. This is a kind of
> wms.
> 
> My question: What is the best solution to implement this kind of
> architecture?
> Has anybody already done such thing?
> 
> My ideas were to use WDDX (Web Distributed Data Exchange,
> http://www.openwddx.org/faq/) to exchange the required parameters between
> the
> mapserver box (coordinates of the click, shapes ON,...) and the webserver
> boxes
> (url of the map image,...). So the Webserver (php enabled) would post a
> wddx file
> (containing the serailzed parameter) to the MapServerPHP-MapScript. After
> deserialization PHP/Mapscript will process the map request and return wddx
> file
> (containing the url of the images and other important parameter).
> 
> Is it the way to go to get good performance? Is there a better way to do
> it?
> 
> Other question: I was palnning to start this development using directly
> Mapserver
> 3.5, providing that the system will not enter in production before
> november. Is
> 3.5 stable enough? Any timesacle for the official release?
> 
> Claude Philipona