Hi TAGers,
I am deep in the review process for the proposed changes to Darwin Core, trying to do due diligence. Some of the change requests are challenging to summarize to determine if there is consensus, in spite of, or because of the discussions. One of the requests on which I’d like some TAG help before proposing a solution is the request for the inclusion of the terms from the geo: namespace (xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#").
Support in tdwg-content for this request comes from multiple independent sources. There has been a long history of discussion (http://lists.tdwg.org/pipermail/tdwg-tag/2010-August/000050.html), beginning in anticipation of the 2010 TDWG BioBlitz. The proposal has gone through the minimum 30-day public review and discussion on the forum tdwg-content@lists.tdwg.org:
http://lists.tdwg.org/pipermail/tdwg-content/2011-July/002581.html
There seems to be general support for the additions, however, after reviewing the discussions and the references. I have the following observations/concerns:
1) The discussions presented geo:lat and geo:lng as W3C standards. This is not actually the case. These terms were created by the W3C Semantic Web Interest Group in 2003. The documentation for these terms (http://www.w3.org/2003/01/geo/) states:
"This document was created as an informal collaboration within W3C's Semantic Web Interest Group. This work is not currently on the W3C recommendation track for standardization, and has not been subject to the associated review process, quality assurance, etc. If there is interest amongst the W3C membership in standards work on a location/mapping RDF vocabulary, this current work may inform any more formal efforts to follow."
These terms do seem to have widespread usage in the semantic web. Should we be concerned that they are not part of a standard?
2) geo:lat and geo:lng are not semantically equivalent to the existing Darwin Core terms decimalLatitude and decimalLongitude, which have been a part of the Darwin Core since it 2003 (or before, if we ignore the missing Datum term in earlier versions). The addition of the geo: terms as a third set of geolocation terms for Darwin Core raised concerns about confusion. I share this concern. An option would be to adopt these terms and deprecate dwc:decimalLatitude, dwc:Longitude, and dwc:geodeticDatum. Data that would have occupied these terms would go instead to dwc:verbatimLatitude dwc:verbatimLongitude, and dwc:verbatimSRS. I see a couple of problems with this. First, most of the time the data in the decimal coordinate fields are not the verbatim originals, so this would be a misuse of the Darwin Core terms. Second, this change would make it more difficult for data consumer’s to use existing georeferences. Here’s how. Right now the verbatim fields are meant to hold the original coordinate information, which means they have a wide variety of content - everything from UTMs to custom-encoded coordinates, in any conceivable format. Meanwhile, the data in the decimal coordinates fields can be much more readily transformed into the desired standardized spatial reference system afforded by the geo: terms, because the values are at least standardized on decimal degrees and only a datum transformation has to be done on them.
Do we abandon the dwc: terms decimalLatitude, decimalLongitude, and geodeticDatum? Do we abandon them now? Do we build the simplest possible tools necessary for anyone to do the transformations so that these terms are no longer needed? If so, do we wait until those tools exist?
3) Additional concern was expressed that the term geo:alt should also be added. No one has made a formal request for this. However, if the other geo: terms were adopted, it might be silly not to adopt this one as well. Doing so would raise a host of issues similar to those raised for lat and lng.
I don’t have a good solution. The best short-term one, in my opinion, is to leave Darwin Core as it is, and to recommend that if applications (or aggregators) want to share “cleansed” point-based georeferences, that they do so with the geo: tags, the values for which they derive through transformations to WGS84 of the DwC decimal coordinates and geodeticDatum.
Options:
1) Accept the proposal, adding geo:lat, geo:lng, and geo:alt to the list of recommended terms for DwC.
2) Reject the proposal pending further directed research into a comprehensive solution that considers all geospatial terms in Darwin Core (including footprintWKT, for example).
3) Reject the proposal for now, reopening the public discussion with these concerns.
Others?