Re: [Geoserver-devel] client for Geoserver and Utlities map

[<ch...@op...>]

> I am pretty new to geoserver and I am still reading all relevant
> documents (including OpenGIS docs since we are not map experts) to
> better understand the platform but first I want to congratulate you
> guys for this excellent software.
Thanks!  We love positive feedback.

> With a group of university students (java and other programming
> skills) we are thinking about using GeoServer to serve as a base for
> a GIS with an SVG for, in a first step, a read-only client.
> The target at first would be small utilities such as electricity or
> water companies, therefore we are talking about network map such as
> low voltage cable or water pipes. We believe this could benefit to a
> lot of small utilities that much of the time cannot afford to pay for
> big propriatory solutions.
Sounds great.

> We could not find an open-source solution for this specific area
> that's why we are thinking to use Geoserver as a base to read
> shapfile and/or connect to PostGIS/MySQL.
Cool.  MySQL is actually about 4 hours away from being available as a
datastore for GeoServer, I just need to find the time to make a few
fixes and package it up for people to start testing.  If you need it
let me know and I can probably put it up for you pretty quick.  The
code is all in geotools, it just needs to be compiled and made
available for download.

> GML and SVG
> We are also wondering whether we should transform the GML on the
> server side or on the client side (as it is currently in GeoClient).
> For the sake of speed I will intend to do that on the server side
> (but breaking as such the WFS).
> WFS seems more appropriate than WMS although the late one can deliver
> SVG but does not interact as such on the feature level.
Well we actually already have limited SVG support in the WMS, which I
guess sortof answers your question, we felt that WMS was the way to
deliver it initially.  But I think it's definitely up for debate if wms
or wfs should serve svg.  I feel that the WFS should not be broken, and
I think that svg can specify additional attributes (correct me if I"m
wrong, it's been awhile), so I think if the WFS returned svg it should
try to return feature attributes.  I'm not a huge fan of breaking the
WFS to not return attributes, though that said our current svg
implementation sort of breaks the WMS, as we have not yet implemented
styles for it.  So I would say you should extend the current SVG wms
support, which builds straight from GeoTools2 features (our internal
objects, this might be good motivation for me to put together a better
developers guide).  If you want to you could also add it as an output
format for the WFS, we did a bit of redesign to make that easier to do
(feel free to ask specifics, I'm just painting broad strokes now).

I'm not sure what you mean by WMS not interacting on the feature
level...
If you mean filtering capabilities, well the WMS _can_ actually do that,
but it's sort of round about.  The Styled Layer Description (SLD)
language (it's an ogc implementation spec) specifies how to draw the
features, and it can work with filters, coloring some a certain color,
returning some not at all, ect.  GeoServer supports SLD for it's
filters, but to be truly useful it would need to be a SLD-WMS, which
allows users to include their own SLD in their request.  GeoServer is
relatively close to implementing full SLD, I'd estimate 2-3 weeks of
work, if not less if you know what you're doing.

GeoServer also has a bit more of a hacky approach for filters with WMS,
we just added a FILTER element, used just like the WFS, to return the
features wanted.  But again, I'm not sure if by 'interacting on the
feature level' you mean filtering, or something else...

> Client
> Another point is that to my knowledge there is not yet a working
> version of an open source client with GeoServer. Our first objective
> is probably to develop one (most probably based on GeoClient) to work
> correctly with GeoServer.
That would be great, good clients are where GeoServer is really hurting.

> Here are a few questions before we make a wrong decision!:
> - Are you aware of any solutions in this area (of course open
> source!)?
None that are really that good and open source.  I've been contemplating
working on one, as there just aren't many good ones out there.  Ideally
there would be quite a few, in a number of different programming
languages, that different projects could customize to their needs.  The
best going right now is definitely moximedia's IMF, but unfortunately
it's not open source.  In the open source area there's geoclient, but
their developers have moved to community map builder:
http://mapbuilder.sourceforge.net/  They might have some better pieces
for you to build upon.  But if you have a decent sized group I might
recommend just writing your own, in whatever language you guys are most
comfortable with.  I don't keep very good track of client applications,
so there may be something out there that I don't know about.

Ok, just started a page on the wiki, with David's and Saul's info, if
people could please add to it that would be great.  Sometime soon I'll
try to test out more clients and clean up that page into something more
useful.

> - Is OpenGIS standard and Geoserver WFS server well suited for this
> kind of specific mapping application?
Echoing Saul, yes definitely.  The OGC specs can definitely handle your
needs, and doing things in a standards based way gives you a lot of
benefits, you'll be able to seamless combine your map data with other
wms and wfs servers, and others will be able to access your data from
their own clients.  And the OGC has done a lot of good thinking on how
best to handle these sorts of problems.


> - is hard to find on the usermap a live example using geoserver, any
> good reference?
This is the other place GeoServer is hurting.  You're really just asking
about all my todo's ;)  I'd like to set up a whole bunch of free data
on a solid GeoServer instance, but just haven't gotten to it.  A good
client app would also be key for that.  Hopefully in the next couple of
months I'll start something up.  But note that the usermap itself is a
live example of GeoServer.  The rendering is not yet geoserver, but the
inserts and querying of the users makes use of the WFS capabilities of
GeoServer.

> - Is there any team working on a client actively (I've seen request
> on Jira and some few suggestions for a WMS client, and Geoclient is
> not really developed anymore)? or should we start one from scratch?
If a desktop client suits your needs then you should definitely link up
with uDig.  If you're doing web mapping then getting in touch with the
community mapbuilder folks might be good, but I feel like they may have
moved on to other projects.  There might be some good pieces there.

> - I still do not understand very well how a datastore is working.
> Here is my understanding (only for database) : each FeatureType
> should have its own table in a database. This table has a FeatureID
> as primary key and a Geometry field. For the rest of the table it can
> be specific attributes for each FeatureType such as the size,
> topology or connectivity for electric cables. Am I correct?
Yes, exactly.
> How geoserver can use them (if even possible)?
Well GeoServer returns all attributes as properties of the GML returned
in a GetFeature request.  You can also do all sorts of filtering
against the attributes, both spatial and non-spatial.  See the OGC's
filter specification for more information, GeoServer fully supports
every filter there.

> Ok, I stop here, my email is already too long!
No worries, keep them coming, I'm more than happy to respond.

> But be sure that we
> are interested to participate to this project.
Great, I'd be really excited to get a good client and a good sample
application, and am more than happy to help you out in any way I can. 
I may even be able to help out with some of your client development
tasks, if it lines up with what I want to do.  What I really want is a
generic WFS transactional client, as I think a lot of cool projects
could be done with that.  For your project it could be things like
allowing companies to update the locations or properties of the pipes
or electric lines through your client interface.  And the great thing
about open standards is that they could also do it through a uDig
desktop client or any other WFS-T client.  Personally I'd like to be
able to make maps that users can annotate and add to as they please.

best regards,

Chris




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