OwsNotes / !DataServicesProposal

= Service Proposals =

== Implementing a CSML-API service ==

A minimal CSML API must be able to do the following with a CSMLDataset
 1. Serve the CSMLFeatureCollection element.
 1. Expose the CSML affordances associated one of its CSMLFeatures.
 1. Serve the output of CSML affordances as a CSMLDataset + associated
    data files.  This will be called a CSMLBundle.

Optionally it would also be useful to:
 1. Serve parts of the CSMLFeatureCollection for efficient querying of 
    properties such as grid axes and units.

OwsNotes/OgcServicesReview discusses how the different OGC services could be used to
expose CSML affordances.  Based on that page and the premises above we could
implement a CSML-API service as a combination of WFS and WPS services:

=== A Basic WFS service ===

This would serve CSMLFeatureCollections.  Querying parts of the
CSMLFeatureCollection structure would be suppored using XLINK property
queries.  A nice additional feature would be to allow delivery of
features as JSON for easier AJAX client integration.

=== A WPS-affordance service (WPSa) ===

CSML affordances would be implemented as WPS processes.  Each process
would produce a CSMLBundle output.  We would need to decide whether
affordance operations block until complete or whether the WPS store
function must be implemented.  WPS-store adds more flexibility and
better response but requires cache control.

== Implementing visualisation services ==

We want to:
 1. Plot geospatial data as lat/lon horizontal slices.
 1. Overlay one feature upon another.
 1. Produce both "quick-look" and "publication-quality" images.

Work on the IPCC DDC provides a good prototype for what is possible.
We could again implement a pair of OGC services.

=== A WMS service ===

The IPCC DDC already serves CSML GridSeries features through a WMS.
More work is required to make this code more generic (in particular
mapping the WMS and CSML data models).  Other features that can
usefully be viewed as a projection in lat/lon could be renderred to
images and served via WMS, for instance trajectories.  Tools such as
OpenLayers can then be easily configured to overlay WMS sources.

=== A WPS-vis service (WPSv) ===

Publication quality plots and plots that aren't lat/lon projections
(e.g. timeseries) would be serves as a WPS.  The IPCC DDC currently
implements this as a custom request on the WMS server.  A WPS could
support queueing of requests that might take a long time
(e.g. animations) using WPS-store.  Overlays could also supported with
more coding time (but also see OwsNotes/CrossSiteIssues).