The 52°North WPS implementation shares one important property with the specification – it is very flexible and can be used for many different use cases. A number of parties contribute, which results in a number of active development branches for code. We will present a selection in blog posts over the next few months.
Spacebel takes the 52°North WPS to space.
Their extensions target the requirements of satellite data processing with service oriented architectures for a future proof and flexible infrastructure. A processing on-demand WPS extension allows the user to dynamically deploy and un-deploy processes, as well as auxiliary data, steer the execution of processes, monitor/audit the executed processes, download processing results, and discover processes and workflows.
These features are developed to support the Heterogeneous Missions Accessiblity (HMA) on-demand processing scenario , in which earth observation (EO) data shall be processed. This is mostly satellite data and therefore comes with a few challenges, most importantly, the sheer size of the data. The volumes are so large that this will never work without processing power close to the data (no remote internet access) and a parallel processing infrastructure, such as a Grid Computing or Cloud environment. This way, an analyst/a scientist must not run his own processing facilities, but can remotely start and control processes. Overhead for data transfer are also minimized. Such a framework additionally allows users of the processing chains to share deployed processes.
Moreover, these developments allow encapsulation of all forms of processing, be it Grid processes or workflows based on workflow engines – the WPS provides a common interface for deployment, execution, and monitoring. This also enables flexibility and independence from actual Grid installations and allows users to deploy the WPS in a modular hierarchy for different missions and ground segments – typical organizational elements of the space community.
So much about the concepts – but what about the implementation?
Building upon the 52°North implementation of WPS 1.0 and WPS-T, Spacebel implemented the following new operations and features (see  for details).
- GetStatus and Cancel operations for flexible process handling.
- DeployData, UndeployData and DescribeData operations for discovery and handling of auxiliary data (e.g. a landuse layer).
- GetAudit for accessing processing execution traces.
- Transactional backends (a.k.a. repositories) for Apache ODE as a process manager for workflows and the JavaSAGA process manager for Grid processes.
- Callback feature for asynchronous status updates (without polling) about process completion and failure, which enables efficient workflows, for example if several web services are chained.
Some of these are now parts of the change requests (CR) for the upcoming WPS 2.0 specification. So with these implementations already in place, the 52°North WPS is in good shape for adopting the envisioned standard specification.
They defined a SSEGrid (Grid Enabled Service Support Environment) WPS Application Profile based on these operations. This profile further defines the inputs and outputs and the extended features for process management and their formats (e.g. Apache ODE event list for audits). Below is a screen shot of the Processing Application of the SSEGrid portal. It shows the running tasks and elements to check the process’ status, but also to download the results once the process is finished (see red highlights).
The developments described above were made as part of the SSEGrid technology project  financed by the European Space Agency (ESA). Further evolution of the standardization work is expected through the forthcoming HMA for Science project, which will start in January 2013.
Please get in touch with Patrick Jacques if you are interested in documentation and more details about these developments. Spacebel is an active member of the OGC and these developments are planned to be used for an extension “WPS-G” once the WPS 2.0 specification is stable – we look forward to discussing that within the OGC community!
Spacebel is a software engineering company for the space market for advanced IT solutions and services. The company operates in the Space and Earth monitoring applications sectors, serving space agencies, government departments, major aerospace companies, European institutions, as well as the commercial market. They are active in several domains, mainly earth observation, space flight, and science, but also telecoms, navigation, exploration, launchers, balloons and space situational awareness.
The European Space Agency (ESA) is Europe’s gateway to space. It’s mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
So to wrap up, thanks (and congratulations) go to the bustling Spacebel developers and software architects who developed such powerful functionality and especially to Patrick Jacques and Christophe Noël who allowed us to reuse some of their graphics and documents as a basis for this article. “Heterogeneous Missions Accessibility” section 5.5.5 at http://esamultimedia.esa.int/multimedia/publications/TM-21/TM-21.pdf
 “Processing on-Demand WPS Extension (WPS-G) Specification (Draft)” at http://wiki.services.eoportal.org/tiki-download_wiki_attachment.php?attId=1645
 ESA “SSE Grid Project” at http://wiki.services.eoportal.org/tiki-index.php?page=SSEGrid&highlight=SSEGrid