1. DELIVERING ENVIRONMENTAL WEB SERVICES (DEWS) Partners: UK Met Office (Lead Partner), British Atmospheric Data Centre (BADC), British Maritime Technology (BMT), Environmental Systems Science Centre, University of Reading (ESSC), IBM, Lost Wax DEWS aims to demonstrate through two specific case study examples, in the Marine Safety and Health sectors, the powerful capabilities that Web Services can offer, to examine the benefits and shortfalls as they stand at present, and importantly, to promote early adoption by potential users of these technologies in an open architecture/open source environment. In addition the project also expects to deliver a range of new open source tools, Web Coverage, Feature and Map Services and OGC- compliant, XML-based data standards.

2. DEWS Architecture

3. Grid Access Data Service (GADS) and WCS GADS is a Web Service that provides access to gridded climatological data –hides details of data storage from users –supports a number of file formats (e.g. netCDF, GRIB) ESSC has used GADS for several years to serve data However GADS does not follow any convention or standard –In DEWS we are modifying GADS to be OGC WCS compliant

4. Limitations of WCS 1.0.0 The current version of the WCS specification (1.0.0) is not quite fit for purpose for DEWS requirements: –Does not officially support NetCDF –Does not say anything about security –Assumes data are returned to client as a direct response to the request (i.e. synchronously) –Not possible if extraction request takes a long time or needs to be enqueued Some of these are addressed in WCS 1.1.0, but this version is not quite ready yet –So we're working from 1.0.0

5. File format: –Support only NetCDF with Climate and Forecast (CF) convention –Format specifier will be "CF-netCDF" (GALEON) Security: –Use NERC Data Grid security mechanism –Based on WS-Security –Only GetCoverage operation needs to be secured –GetCapabilities and DescribeCoverage must be unsecured (Met Office requirement) –Clients will be SeaInfo (a BMT system), portal users (humans) and others How is WCS modified for DEWS?

6. How we shall modify… (2) Synchronous delivery of data is not generally acceptable because of large data volumes –Data extraction process may be long, client can't leave connection open Also, BMT have requirement to uniquely identify each data request for audit purposes Implies client must be provided a "ticket" for each data request –Client then uses the ticket to poll for progress and retrieve the data We borrow from the Web Processing Server (WPS) to define this ticket

7. Asynchronous data delivery Enables queueing of large data requests, but still permits synchronous handling of small requests –and backward-compatibility with WCS 1.0.0 Two key parameters (taken from WPS spec): –“STORE = true” means “return a pointer to the data, not the data itself” –“STATUS = true” means “give me access to a status document that tells me the progress of my data request” Fully-asynchronous delivery with both STORE and STATUS set to “true” Fully-synchronous delivery (WCS 1.0.0 compliant) with both set to “false” (or omitted) GADS-like delivery with STORE=true, STATUS=false (STATUS=true and STORE=false has no meaning and is disallowed)

8. Geoserver Geoserver is an Open Source server that connects information to the Geospatial Web. We decided to develop our WCS based on Geoserver. This enables us to plug into a larger community. Geoserver already provides an implementation of WMS, WFS and WCS. However, WCS support in Geoserver is experimental and focused on 2-D images, rather than 4-D data.

9. Geoserver WCS and GADS In summary we would like to: –Augment Geoserver’s WCS capabilities to serve 3D or 4D geospatial data –Support simple subsetting of 2/3/4D gridded data –Provide asynchronous data delivery (due to large files) –Secure data access. Geoserver is based on the Geotools library –Geotools historically 2-D focussed –But 4-D Geotools is coming soon –However, in DEWS we currently bypass Geotools and use Geoserver just as a thin wrapping service layer, using GADS as backend for extracting data/metadata

10. Geoserver Architecture DB GADS LIBRARY CSML Common Interface Spring J2E GEOTOOLS Platform Core platform module Data Catalog of data resources Struts WFSWMSWCS Validation WFS-T data integrity Main Servlet and configuration WEB Web config application

11. Prototype

12. Future Expect to have prototype online early in New Year “Operational system” by July 2007 Other work (out of scope for DEWS): –WCS 1.1.0 compatibility –Integration with 4-D Geotools