Actually, my decision to take up Semantic Google Maps was mostly a function of the fact that it was truly a dead project, unlike SL. :) Also playing a small part was the fact that the Google Maps code was conceptually simpler for me to understand than OpenLayers.

I don't think it would ever make sense to merge SGM and SL, for the simple reason that Google Maps is not open source, and thus, I think, has to be quarantined away from the truly open-source stuff (am I missing something here? I thought that was one of the main reasons for creating Semantic Layers in the first place).

That's great that you're working on the technology, and that the OpenLayers people might be helping you. So I guess the problem is that the earth is a sphere instead of a square? :) I do think that the future of Semantic MediaWiki lies with OpenLayers and other open-source solutions, as opposed to proprietary technologies - the proprietary stuff might be easier to deal with in the short term, but in the long run there are good pragmatic reasons not to want to deal with API keys, permissions, and license agreements. So I'm looking forward to the day when everyone has switched to Semantic Layers, and along with that the day when the technology is as easy to set up as Google Maps currently is.


On Tue, Jul 8, 2008 at 11:24 PM, Matt Williamson <> wrote:

Semantic Layers and I are still around, and I've done some initial work on integrating OSM with Semantic Layers.

The only problem is that OSM uses a "Spherical Mercator" projection--similar to Google Maps--but so far I've built the extension around the use-case of only using one projection, and usually with the "lonlat" (aka EPSG:4326) projection in mind. It can certainly work with other projections, but when you start mixing different projections, things stop working together properly. Also, unless you can translate between latitude/longitude coordinates and the target projection with its units (basically converting lat/lon to meters in OSM's case), you can't use SMW's Geographic coordinate data type (or even two "number"s that store a lat and lon, for that matter) to plot things on the map. Now, OpenLayers *should* be able to do this, I believe (it does it successfully for Google Map imagery), but I haven't gotten it to work yet.

Suffice it to say, I'm sure it can be done, and I intend to do it--it's just tricky.

And Yaron: Sorry, I imagine your willingness to take up Semantic Google Maps is largely due to my sluggishness in delivering the promised integration with Semantic Forms :-) sorry, I am still planning to do that!

I don't know if it's possible, but perhaps we should consider merging these extensions somehow? I would imagine many of the features you will want to add to SGM are things I've already at least started in SL, so it would seem unfortunate to duplicate effort. Ideally, we'd be able to modularize the rendering system, and just pick which one you want to use...but the APIs and perhaps capabilities are so different that may not be feasible.

By the way, I actually had some folks from MetaCarta (the creators/sponsors of OpenLayers) contact me about developing SL into something they can leverage/distribute, but they haven't gotten me the firm requirements yet (guess I need to bug them again), but that could be exciting. It might involve licensing problems, though, as they want something BSD...which I think I could do, if I removed the remaining SMW-derived code, but I'm not sure.


On Jul 7, 2008, at 2:31 PM, Yaron Koren wrote:

I definitely know about the OpenStreetMap project (and, as a side note, I'm looking forward to meeting some of their developers at Wikimania next week), but I think that application is better suited for Semantic Layers, which is the extension based on OpenLayers. Matt Williamson, the developer of Semantic Layers, has said he's interested in adding OpenStreetMap information to SL (I believe it can just be implemented as a separate layer), but I don't know what the status of that is.


On Mon, Jul 7, 2008 at 3:57 PM, Dan Brickley <> wrote:
Yaron Koren wrote:

After almost a year of inactivity for the project, I've taken over the Semantic Google Maps extension.

I encourage everyone who already uses this extension to upgrade to the latest version, and everyone else to take a look at it.

Great that it's actively maintained again! :)

Can I encourage you to think about adding support also for OpenStreetMap? They're a great project, very active community and with similar goals (open data) to SMW...




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