Hi, I suppose those clients are all using either geotools, deegree of ogr internally but I am not sure. Somehow I feel that Geotools might suit OpenJUMP but I am not a developer but just a user.
Reading GML is not the biggest problem with WFS any longer. Some programs may not know what to do with some data types, like xs:short or xs:long. Some may forget to initialize the attribute table with all the attributes which included in the schema if the first record in the GML part does not contain all the attributes and so on but there are less and less pure parsing errors. Biggest troubles seem to be now with WFS 1.1.0 and GML3 and the axis order. There cannot be a single software in the world handling all the cases correctly. Nor a single person who can say how they really should behave. Axis order trouble reflects to building correct spatial filters, which seems to be difficult to do in such a way that all different WFS servers accepts them even with coordinate systems like UTM which do not suffer from the axis order mess. Even adding a bounding box into GML3 filter can lead to failure because there are ridicuosly many ways to do it. I feel that WFS 1.0.0 with GML2 was still a relatively simple and usable standard. Unfortunately nobody cares to correct the remaining troubles with it because there are versions 1.1.0 an 2.0.0 around and those are requirement for the Inspire datasets, for example. There must be new troubles to come with application schemas (instead of simple feature ones) and things like real GML3 curves etc. Some WFS servers can deliver data also in other formats than GML. It is allowed, but as you wrote, a really good alternative is missing. Shapefiles with geometry type limitation and short field names etc. are not at all ideal and I suppose that Geojson is not featurerich enough. -Jukka Rahkonen- Martin Davis wrote: > > If all those other platforms are able to handle WFS reasonably well, > that seems to take the wind out of my statement that GML is > too hard to > implement! Perhaps some of them are implementing a sane > subset of GML, > which would be easier to implement. I suspect there's an 80-20 > situation here, where most WFS servers are only serving up fairly > straightforward GML. (Seems like you still need to parse the schema, > though, which is hard to see how that could be made simple). > > It would be nice to look at the implementations, and follow whichever > one looks easiest for OJ as well. > > But in general I share your frustration about GML. It > originally seemed > like the answer to an open spatial format standard, but the > complexity > of it is a huge barrier to entry. (In my wilder moments I > daydream that > It would be nice if the open-source geospatial world got together to > define a new standard format which would be more practical to > implement.!) > > Martin > > On 8/18/2011 7:21 AM, Rahkonen Jukka wrote: > > Hi Martin, > > > > I just get frustrated every now and then with WFS and GML. > It is so simple to get for example the railways from WFS with > > > http://188.64.1.61/cgi-bin/tinyows?service=wfs&version=1.0.0&r equest=GetFeature&typename=lv:mml_railway > > > > I can see the GML on screen and it looks pretty > understandable with all the attributes and geometries. With > a pencil and cross-ruled paper I could even draw the > geometries. Then I save the result on disk and believe that > everything is OK and I have received a nive set of geospatial > data. But actually there are not very many free GIS software > being able to open and show the data that was saved on a > disk. Schema is missing (nobody told it should have been > loaded as well, and the link to schema inside GML does not > help you much when on the field off-line), gml cannot be > parsed and so on. What have we done to deserve these > standards? Not to mention the advanced axis order frustration > with WMS 1.3.0, WFS 1.1.0, WCS 1.1 and GML3. > > > > Situation with open source WFS clients is actually rather > good now, finally. OpenJUMP does not work any more (or it may > with deegree servers but not with others) but Kosmo GIS, > gvSIG, QGis and iGeoDesktop are usable as well as uDig and > OpenLayers. And for me it is not so big trouble to convert > GML from disk into other formats with OGR. However, I would > like to teach others to do it in some extremely simple way > and not through additional downloads and command line > workarounds. Nowadays people tend to give in or escape > immediately when they see an open command window. > > > > -Jukka Rahkonen- > > > > Martin Davis wrote: > > > >> Jukka, > >> > >> I may be mis-understanding your post, but the difficulty > with reading > >> GML2 from WFS is the same as reading arbitrary GML2: GML > >> schemas can be > >> very complex, and thus it's very difficult to develop a > >> general-purpose > >> GML2 Reader. > >> > >> That is the reason that JUMP implemented the simplified GML2 > >> readers for > >> JUMPGML and using a GML template file - to avoid having to > >> parse and map > >> general GML2 schemas. > >> > >> Obviously it is possible to parse general GML2 - GeoTools > has a GML2 > >> Reader, for instance. This might be a better direction to go in to > >> bring full GML2 capability to JUMP. > >> > >> Martin > >> > >> On 8/18/2011 1:31 AM, Rahkonen Jukka wrote: > >>> Hi, > >>> > >>> OpenJUMP has a native reader for GML2 but it requires a > >> schema file in the native JUMP format. > >>> On the other hand, WFS 1.0.0 server is sending data as GML. > >> If you want to get some, use the following link, show the > >> source code on a browser and save file on disk > >> http://188.64.1.61/cgi-bin/tinyows?service=wfs&version=1.0.0&r > > equest=GetFeature&typename=lv:mml_railway > >>> The data comes without schema but it can be read from WFS > >> with another request: > >> http://188.64.1.61/cgi-bin/tinyows?service=wfs&version=1.0.0&r > > equest=DescribeFeatureType&typeName=lv:mml_railway > >>> Now I wonder if it could be possible to make OpenJUMP to > >> understand also the WFS schema in addition to the native JUMP > >> schema file so it could parse the GML that comes from WFS? I > >> have tested that SkyJUMP can convert GML into shapefiles with > >> the included iGOR utility but I wonder if GML could be read > >> more directly. > >>> -Jukka Rahkonen- > >>> > >> -------------------------------------------------------------- > >> ---------------- > >>> Get a FREE DOWNLOAD! and learn more about uberSVN rich system, > >>> user administration capabilities and model configuration. 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