[OpenLayers-Users] question about OpenLayers.Format.GML.v2

[Bart van den Eijnden (OSGIS)]

Hey Tim,

a use case for us is for instance grouping of entities (e.g. water 
bodies), which can consist of points, polygons and lines. So we have a 
typename for points, one for polygons and one for lines. They are 
grouped as 1 WMS layer. When we want to display the attribute table of 
that layer, we need to display (features from) 3 typenames. And ofcourse 
it's a shame to use 3 separate WFS requests for that.

Also to search for objects, we sometimes need to go over 15 separate 
typenames using the same Filter.
If we want to display all the details of a certain feature, we also need 
to query a lot of typenames.

Indeed I intend to use the Protocol.WFS separate of a vector layer in 
this case. I can imagine this is not the most common use case and I 
understand your concern about first getting the basics solid.

I'll be looking into the whole Protocol.WFS stuff more next week (I 
started today), and hope I can come up with more testing and maybe some 
contributions.

Thanks for all this great work btw!

Best regards,
Bart

Tim Schaub wrote:
> Hey-
>
> bartvde at osgis.nl wrote:
>   
>> Hi list,
>>
>> the constructor of the new GML2 parser gets a featureType parameter.
>>
>> Does this mean that if a GML file contains multiple featureTypes, that I
>> have to call read multiple times, and append the results myself? Will this
>> be as efficient as doing the parsing in a single round?
>>     
>
> Yeah, this is because up until this point, vector formats have been used 
> to read/write collections of features, and I think of collections of 
> features as layers.
>
> I'd like to continue thinking that way (because I think it works).  But 
> I know there are people who are interested in making WFS requests for 
> multiple feature types (which I like to think of as layers).
>
> I really want to get WFS working for the most common cases.  And I want 
> it to be solid (with good support for transactions and filtered 
> queries).  I've made a boatload of changes in the topp/wfs sandbox - 
> including changes to the GML & Filter code.
>
> My spare energy will be focussed on getting this code (the WFS protocol 
> and related GML & Filter changes) in to the trunk.  Modifying the 
> existing GML code is a bit at odds with that.
>
> I also know that it will make sense to have the protocol be used in the 
> absence of a layer.  And of course we want to support our OGC protocol 
> power user(s).
>
> Bart, can you describe (perhaps again) where you want to make a single 
> request for multiple feature types.  I'm sure it is done all the time, I 
> just usually see a way that I think it simpler, so I'm curious to hear 
> more use cases.
>
> Tim
>
>
>   
>> Best regards,
>> Bart
>>
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>>     
>
>
>   


-- 
Bart van den Eijnden
OSGIS, Open Source GIS
bartvde at osgis.nl
http://www.osgis.nl