[udig-devel] GML loading - over the top?

[Vince Darley]

Jody,

At 19:45 12/09/2007, Jody Garnett wrote:
>Your file however does not contain all the information needed; often 
>for a roadMember you will end up with a networkMember refered to by 
>an xlink:href='#xxxxxx' - and that ID is not used anywhere in the 
>file. What are you expecting us to do in this situtation?

I'm not sure really.  It could perhaps be that the reference is in a 
another .gml file (they typically send lots of chunks, ranging in 
size from a few k to a few megabytes) - we might have 60 or more GML 
files for an area with a population of 100000 people.

Some of these references would appear to be in different layers, for 
example this one:

                 <osgb:referenceToTopographicArea
                                 xlink:href='#osgb1000001795448371' />

The 'topographic' layers from OS are generally supplied separately as 
far as I am aware.  The layers we care most about are the topological 
ones: ITN and RRI, and the Address information.  These are needed for 
routing purposes.  Topographic layers are only needed to draw pretty 
maps (clearly useful, but not essential to us).

--

But, more generally, aren't there always going to be dangling 
references at the edges of any topologically sound data of, say, a 
road network.  This particular data contains not just geometries for 
visualisation of the roads, but also the connectivity information 
(this road has these 2 junctions at its ends, those junctions connect 
to these other roads, etc).  This means at the edges one will surely 
always have unknown references?

Do take all the above with a pinch of salt, since I've not really 
digested the GML spec nor OS's use of it.  (and I was hoping not to, 
really... ;-)

The freeware Snowflake GML viewer manages to load all this data and 
visualise it very nicely, however, so I can at least assure you the 
data is good!

cheers,

Vince.