Copyright © 2014 Open Geospatial Consortium
29 The following is an example invocation of the nearest neighbour stored query that returns
the nearest objects of type “Mountain”: http:www.opengeospatial.orgserver?service=WFSversion=2.0request=GetFeature
storedQuery_Id=urn:cw:def:query:OGC- WFS::NearestNeighbours:ByLocationTypeNamelocationTypeName=mountainlat=45
.288278lon=-66.062351srsName=urn:ogc:def:crs:EPSG::4326count=10
8.5.2.4 Parameter discussion
All parameters are mandatory.
8.5.3 Bounding-box search
8.5.3.1 Introduction
A bounding-box BBOX search finds objects within a coordinate rectangle. It applies to all feature types listed in the request.
8.5.3.2 XML encoding
The BBOX operator was used for this capability, for example:
ogc:BBOX ogc:PropertyNameiso19112:positionogc:PropertyName
gml:Envelope srsName=urn:ogc:def:crs:EPSG::4326 gml:lowerCorner44.8755955883576 -
66.8650672925836gml:lowerCorner gml:upperCorner45.6188750089766 -
65.3198488862554gml:upperCorner gml:Envelope
ogc:BBOX
8.5.3.3 KVP encoding
The following table defines the KVP encoding for the BBox operator:
Parameter Name Expected Type
LowerCorner longitude Number
LowerCorner latitude Number
UpperCorner longitude Number
UpperCorner latitude Number
crs URI optional URI
30
Copyright © 2014 Open Geospatial Consortium
8.5.3.4 Parameter discussion
This encoding allows N coordinates for each corner listed in the order of the optional crsuri. If the crsuri is not specified then the 2-D coordinates shall be specified using
decimal degrees and WGS84
Copyright © 2014 Open Geospatial Consortium
31
9 Architecture Enhancements
Based on the feedback from OWS-9, the basic architecture underlying the Virtual Global Gazetteer shall be improved and where necessary developed.
9.1 Cascading WFS accessing NGA and USGS Gazetteer
As in OWS-9, the Virtual Global Gazetteer has been implemented as a cascading WFS WFS-C. The WFS-C basically behaves towards a client like a standard WFS. Instead
of holding data itself, it cascades the client request to two or more subsequent WFS, which provide the actual data requested.
The major benefit of this approach is integrated access to distributed feature data sets, without the need for a client to explicitly know the underlying service endpoints and
capabilities.
9.2 Architecture
The architecture of the Virtual Global Gazetteer is illustrated in figure 1 below:
Figure 2 - Virtual Global Gazetteer Architecture
On the client side the Virtual Global Gazetteer behaves like any WFS 2.0 service, as specified in OGC 09-025r1.
On the server side the Virtual Global Gazetteer behaves like a WFS client accessing the USGS and NGA gazetteers by cascading the original request to the underlying services.
