Thanks for this. I think a wiki page comparing these various XML type formats with links to various examples eould be extremely usefull - for me at least!
I've had a go at creating this - probably entirely incorrect but perhaps you could correct / add to this? I've marked things with ??? where I am unsure about something or examples seem to be broken or where a simple change would improve the usefulness of the example considerably. http://trac.openlayers.org/wiki/XML I don't want to blunder in and mess up your wiki, but I think maybee a main 'features' or 'overview' page would be good linking from the documentation page - http://trac.openlayers.org/wiki/Documentation which could then link to things such as this XML page On 19/09/2007, Christopher Schmidt <[EMAIL PROTECTED]> wrote: > > On Wed, Sep 19, 2007 at 10:43:33AM +0100, mike wrote: > > Hi, > > > > Is there any documentation of the merits / purpose and intended future > > developments of the various XML layers such as GeoRSS, GML, KML etc? > > Well, the versions in 2.4 were very minimal: Primarily designed to get > people started. Specifically, KML had no polygon support, and was > readonly, GeoRSS was write only, etc. The resutl of this, however, was > that in 2.5 we got both of those fixed: GeoRSS is now a full Atom/RSS > GeoRSS Simple parser, KML supports all KML 2.1 Geometries, etc. > > I have no idea if our GML parser is *valid*, but it has always been the > most complete, I believe because its development was funded as part of > Cameron Shorter's OWS Testbed work. (I could be wrong on this.) > > > They seem to be very similar and almost interchangable, and I'm > > finding this a bit confusing. > > Some day in the distant future, when OpenLayers does everything you need > and new features are just a memory, all Vector Formats will have a > complete mapping of their formats into OpenLayers constructs as best as > the client is able. (This does mean that there are many things that they > will be missing -- For example, we will not be representing the altitude > of KML features in OpenLayers, so far as I can predict.) > > At the moment, they are as complete as people have wanted to make them, > and no more. In some casees (GML, via OGC, and soon I believe KML via > the OWS-5 work), specific Formats have gotten a boost due to outside > funding of development, thus they may be more complete. In other cases > (GeoJSON) the spec is relatively complete and simple in and of itself, > and the authors of the spec happen to be OpenLayers contributors. > > > For example, I'm using GeoRSS to draw markers, and KML to draw lines. > > However, this excellent GeoRSS Serialise example seems to be an edit / > > draw component for lines and polys: > > > http://dev.openlayers.org/sandbox/ahocevar/sldRenderer/examples/georss-serialize.html > > There's actually probably no reason that you *have* to use GeoRSS to > draw markers anymore: it could be done with just a little bit of styling > work on a vector layer. It's not trivial yet, because there is no > pressing business case telling me why I should do it, and presumably no > one else has had one either. > > > Equally, KML boasts support for styles, although this is not > > implemented yet, and if we are accepting the Google definition, then > > KML should support both markers and lines / polys. > > I'm assuming when you say "KML boasts support", you don't mean within > OpenLayers, but in general. If we accept that, we should also support > Photo Overlays and 3D. We can't do that :) However, mapping the full > set of KML data that *can* be represented into OpenLayers is the > eventual goal: just not neccesarily a high priority. > > > Is there a twiki page for this or a good resource I could refer to? > > I'm considering developing this further and I'd like to make sure I'm > > doing the right thing before I start... Also if anyone if actively > > developing in this area I'd be very interested to discuss and see if I > > can help. > > Not really. Docs are the weakest point on the project, but if you have > specific questions I'm glad to answer them, and you can turn them into a > wikipage. Also, I'm often on IRC, irc.freenode.net, #openlayers, as are > 40+ other extremely intelligent contributors to the project, many of > whom would be glad to help. > > > My other point is about combined layers - I'd like to create a layer in > the > > layerswitcher which shows markers and lines / polys (i.e. SVG I > assume). Is > > it possible to make a combined layer or wrap two layers into one in some > > > way? > > Several. But it's likely that you just want to use a Vector layer with > an externalGraphic: see the vector-features.html page for styling > examples. (The only time this wouldn't be true is if you were required > to support Safari 2.) > > Regards, > -- > Christopher Schmidt > MetaCarta
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