CDS contribution to the Infrastructure DS Report

Architecture

Our big picture is that VObs compatibility should be achieved through the addition of a (thin?) interface layer to the existing system. Thus, the whole system architecture has not to be rethought in order to be compatible with VObs standards.
This approach has been tested and validated in the VO-Tech frame, especially to expose some of the VizieR catalogues as SkyNodes.
We have also used this kind of approach in order to integrate records coming from the VObs registries into the GLU system. Indeed, the GLU system was not discarded, we have just added a layer allowing to convert a VOResource record into a GLU record.
For each task we have worked together with the "users", so our work was driven by the needs and not just a technology improvement. For example, in the case of Workflow we also worked on the scientific aspect by the creation of use cases.

Tasks undertaken in DS3

In the framework of DS3, CDS has worked on the following topics :

• Workflows
• Web Services standards
• Implementation of SkyNodes
• ACR
• Plastic
• VObs-enabling Aladin
• CDS publishing registry

Workflows

The main aim of this work is to create Workflow use cases in the astronomical domain and to improve them with tools from VO or IT communities. Workflow is an important concern in many astronomical domains (image, spectra, ...).

• CDS has developped AÏDA (Astronomical Image processIng Architecture) in the context of the MDA (Masses de Données en Astronomy) project (french ministry action). AÏDA can execute worflows and a client-side GUI workflow builder tool (JLOW, Java Libraries fOr Workflow) has been developed in the Cycle 2 of VOTech.
• A collaboration with ESSI to enable Grid access (EGEE, Grid5000) through a middleware component (MOTEUR) is ongoing at CDS.
• The work done has been presented at the OV France Workflow Working Group kickoff meeting (10 November 2005) and discussion about it will be continued at the next meeting (IAP, 16 June 2006).

Web Services standards

The aim of this work is to promote a good Interoperability between the IVOA Web Services. As a large part of the VO services will be based on the Web Service paradigm it might be important to do implement all the services on a common basis.

• VO WS Basic Profile work has started in Boston IVOA (May 2004) meeting and is now in a final implementation phase. This Profile should be a guide about how to implement SOAP Web Services in the IVOA context. It is based on existing work (WS-I) and takes into account the IVOA SupportInterfaces specification. It should become a recommendation by the end of 2006.

Implementation of SkyNodes

The SkyNode has been developed in the frame of the NVO ans is now implemented for a few catalogues. The aim of this work is to improve the SkyNode concept in the case of VizieR which is a very large collection of catalogues (>5000).

• VizieR is a good test case for VOQL/ADQL, as well as for the scalability of the SkyNode protocol. We have tested the JVO and ESAC "SkyNode toolkit" and we have given SkyNode access to some VizieR catalogues using the ESAC toolkit. These first tests and evaluations will allow us to bring our feedback and suggest some improvements to the SkyNode protocol and to the implementation toolkits. A more exhaustive test (at least JVO, ESAC, NVO toolkits, performance comparison with CGI access (overhead, ...), etc.) is ongoing at CDS and a will be published during the VOTech Cycle 3.

ACR

CDS has tested access from a client application (Aladin) to AstroGrid components via the ACR library. The evaluation report is available here.
In that framework, following interactions have been developed:

• access to MySpace: allows one to download within Aladin data coming from its MySpace account
• access to Astrogrid registry : allows you to query the registry, for instance to look for SIAP (Simple Image Access Protocol) or SSAP (Simple Spectrum Access Protocol) services
• launch CEA applications : retrieves available CEA applications from the AstroGrid registry, and allows one to launch them with some user-defined parameters.

Those developments are available in the Aladin prototype version.

Plastic

In the recent past, CDS has gained some experience regarding interoperability between visualization tools (AVO demos, ExtApp and VOApp interfaces, collaboration with VOPlot, STScI, VOSpec and TopCat teams). Relying on this experience, we have participated to the specification of the PLASTIC protocol which aims at easing interoperability between desktop tools.
A PLASTIC-compatible prototype version of Aladin is already available. It allows notably interoperability with tools such as TopCat, VisIVO, ...

VObs-enabling Aladin

Aladin developers' philosophy is to carry on the support of existing or emergent VObs standards as they appear.
In the recent past, support of following standards has been added : ConeSearch, VOTable, SIAP, SSAP
More recently, in the VO-Tech framework, we have added the access to MySpace, the ability to query different services of the Registry (through the All-VO panel) and PLASTIC compatibility
In the close future, we also plan to integrate ADQL support, using the ACR library.

The different developments needed to support those standards allow to test their validity and to bring feedback to the IVOA in order to improve them.

CDS publishing registry

CDS has set up a registry which publishes all VizieR tables. Currently, each VizieR table corresponds to a Resource (giving a total of over 13000 resources). This registry is compliant with the VOResource 0.10 schema. Each Resource contains the full description of the table, with details on the columns metadata (name, units, UCDs), and has type TabularSkyService.

The CDS registry does not harvest from other registries, but can be harvested by other full VObs Registries through the OAI Protocol for Metadata Harvesting. The base URL is http://vizier.u-strasbg.fr/cgi-bin/registry/vizier/oai_v0.10.pl

This registry uses the PERL library developed at Virginia Tech to build on the fly the resource descriptions from the VizieR metadata (extracted from both Sybase RDBMS and ascii ReadMe files for catalogues).

The registry will evolve when VOResource 1.0 becomes an IVOA Recommendation, with im particular an improvement of the Resources description, and the use of UCD1+.