In the OGC Mass Market Geo Working Group meeting yesterday, I presented the preliminary findings of the group brainstorming about the future of KML in the OWS-5 testbed. Most of what was discussed isn’t ready for prime time, so I’ll wait to talk about for a few months, but one critical point that everyone should understand is that KML is, always has been, and will continue to be about mapping/geospatial visualization. Don’t use KML as a data storage or archival format. That’s what GML is for. Yes, KML has some geographic coordinates in there, but KML’s ability to act like a GIS format–attaching other data properties to the geography, typing them, and putting metadata on it all–is weak.
The right way to think about the geographic information “workflow” is to have a spatial database that serves up data to the Web via the Web Feature Service (WFS) API in some flavor of GML. Soon, OGC will specify how that WFS should serve up KML using the existing WFS API plus some extra information to describe the transformation–probably using SLD. The authoritative data will still reside in the spatial database. The KML will just represent one cartographic view of the data at a particular point in time.
September 20th, 2007 at 6:42 am
Raj,
I fully agree with this vision. Just one thing leaves me a little wondering.
When you say:
data + sld = map
well, that does sound a lot like WMS to me.
WFS should be something that returns raw data, not pretty pictures (even thought those pictures are in vector format, with html popup and whatnot).
In fact, in the current GeoServer 1.6.0beta3, you can connect to another WFS server (WFS cascading), use that as your data source, specify an SLD, and call the WMS to either get a classic PNG output, or a KML output that you’ll look into GE.
Just my 2 cents
September 20th, 2007 at 10:00 pm
Andrea, I (and OGC) agree with you, and I should have been clearer on this.
The data + SLD = map concept is implemented as an extension to WMS, and is described in this document on the SLD page: “OpenGIS® Styled Layer Descriptor Profile of the Web Map Service Implementation Specification” version 1.1.0
September 30th, 2007 at 1:57 am
[...] : imaginé pour diffuser de l’information géographique (et rien de plus, comme le rappelle Raj Singh), il intègre aussi étroitement la notion d’interropérabilité [...]
October 18th, 2007 at 8:09 am
[...] Ce petit exemple, permet de ce lancer dans la construction de fichiers KML et ainsi enrichir en information de toutes sortes de cartes dans le vaste “bac à sable” que peut être Google Maps ou Earth. De nombreux scientifiques, les géographes principalement, utilisent déjà ce format. J’ai découvert aussi ce site qui présente Google Earth et le KML pour les enseignants du secondaire. Le KML n’est pas le seul format XML dans le domaine des “géo-formats/2D/3D” : il y a le WMS, WFS et GML venant du monde de la géographie, les formats pour “services web” : AtomPub, GeoRSS et le KML/Z (avec d’autres limites cependant). [...]