GeoServer : GSIP 84 - Control how layer groups are exposed in the WMS capabilities document
This page last changed on Jan 21, 2013 by jive.
Expand the layer group from being just a tool to create base maps to a tool to handle layer trees in the GetCapabilities document.
Choose one of: Under Discussion, In Progress, Completed, Rejected, Deferred
The WMS GetCapabilities contents section contains a tree of layers, which can be used for both brevity and organizational purposes.
Currently GeoServer has a root layer supporting all the possible CRSs, to avoid repeating them for each layer, and then an entry for each published layer.
The layer configuration has a "wms path" property to locate a layer in a particular position in the WMS tree structure, but unfortunately it is not quite usable:
The idea is simple: drop "wms path" and use layer groups as a tool to organize the layer tree in the WMS capabilities. This will work for one level hierarchies, but we envisage also extending the layer group to contain both layers and other layer groups in the short term, thus providing full control over the layer tree structure.
Limited to this proposal we are going to add a new field called groupMode to LayerGroupInfo controlling how the group is exposed to the outside world, with these four tentative values:
In case a layer is included in a any non single group it won't be listed anymore in the flat layer list, although it will still be possible to include the same layer in different layer groups.
The use case of having a layer in the flat list and also in groups does not seem significant, but it is allowed by the WMS spec: if we notice that this is important we can add an extra flag to the layer configuration forcing its presence in the flat list.
The Earth Observation tree is a special mode created to support the WMS EO requirements, in which a Earth Observation product needs to be exposed in its previous form as a layer, and then provide all its detailed contents as new layers that are children of said layers (and using a particular naming convention). When the root of the group is chosen the result is the preview layer, which is normally not the sum of all contained sub-layers.
When the Earth Observation tree mode is chosen, a new field "root layer" will be exposed in the configuration UI, allowing the administrator to choose the "preview" layer sitting in the root of the group.
LayerGroupInfo will have a new "renderingLayers()" method that returns the list of layers to be used to render the group, in particular:
This section should contain feedback provided by PSC members who may have a problem with the proposal.
If the mode is not set the layer group will behave in "single" mode, preserving backwards compatibility for people upgrading GeoServer.
Alessio Fabiani: +1
Chair: Chris Holmes: +1
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