- From: Erik Wilde <dret@berkeley.edu>
- Date: Sun, 29 Jun 2008 11:11:01 -0700
- To: public-geolocation@w3c.org
- CC: straup@gmail.com
hello. > For the sake of argument, the default context could be assumed to be a > WSG84 URI and sorting out what anything else actually *means* is left to > individual developers. (Maybe of handful of known-knowns to deal with > situations where WSG84 is known-known to cause problems, too...) just for the record: while wgs84 is good enough as a context identifier for coordinates, it is not good enough for elevation. > At a minimum, that would allow people to identify what system is being > used for Plain Old Points (tm) and in the hand-waving future leave some > wiggle room for the kinds of things that Erik mentions and stuff no one > has imagined yet. i like the general idea. this would also allow contexts in which no lat/long information is given at all. for each context, there would have to be a definition which parts of a position (lat/log, elevation, uri, bearing, speed) can/must be present, and how they are defined. if it is done that way, there would have to be at least three context identifiers for wgs84 coordinates, though, because elevation should at least be supported for plain wg84, egm96, and barometric values. that looks kind of messy to me (the lat/log values mean the same, even though the context identifier is different). the alternative would be to have parameter-specific context identifiers, may one for lat/log, one for elevation, one for bearing/speed, and my hope would be that uris don't need context identifiers, they should be context-free (or should declare their own context inside of the uri scheme, if context is needed). and i would suggest to not define implicit defaults for context. in most standards, implicit defaults encourage implementers to implement things lazily (i.e., to ignore context parameters and then interpret values in the wrong way, if the context is set to a non-default value). so the position definition should say: if there is a lat/long values, there MUST be a lat/long context specified. if there is an elevation value, there MUST be an elevation context specified... and so forth... cheers, dret.
Received on Sunday, 29 June 2008 18:12:02 UTC