1. www.g-vo.org The AstroGrid-D Information Service Stellaris A central grid component to store, manage and transform metadata - and connect to the VO!

2. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 2 Overview 1. Motivation, or: How and where to connect Grid and VO 2. Stellaris – an Introduction 3. Stellaris Example: Robotic Telescopes 4. VO Applications

3. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 3 1. Motivation What part of the Grid-VO connection are we talking about?

4. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 4 Focus Many different ways to combine VO and a Grid Some are more likely than others notThis talk will not deal with: ”Use Aladin to retrieve and visualise the intermediate results of my grid job pipeline” (data sharing and VO protocols) It can touch: Grid augmented VO publication)It can touch: “On the grid I want to produce (or retrieve) data and publish it via a VO compatible web interface/service, when the user demands so.” (Grid augmented VO publication) Where can we place the connection elements conceptionally?

5. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 5 Grid-VO Connection Principles The Internet Grid Interface http some other p Web Frontend (VO compatible) other VO Service Semantic Web Services Stellaris Grid Compute Resources Grid Storage Resources Metadata Database Interpreter Application

6. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 6 Typical VO DB Requirements A central database that stores and manages scientific metadata Interface to query and the metadata and, possibly, transform it Complies with VO standards Can connect to a web interface or semantic web services (or maybe included in parts) (Scalable and able to handle large or distributed sets of data) Can be easily accessed from grid resources, knows grid technology Common solution: SomeSQL and Tomcat

7. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 7 Requirements II – the grid side Design requirements of Stellaris in AstroGrid-D (2006): A uniform interface to access and integrate the different services Support for flexible and extensible metadata schemes Integration of 1. resource metadata, 2. activity state, 3. application metadata, 4. scientific metadata authentication and authorization for access control.

8. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 8 2. Introduction Stellaris in a Nutshell

9. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 9 Basic Features Stellaris is a database application It consists of a (http-) interface to create, retrieve, update, delete and query metadata. Data is represented in RDF format Queries are performed in SPARQL Virtuoso, sesame and python RDFlib can be used as backend. It offers a separate command line client Fine grained access control through grid security mechanisms and additional means (X.509) Prototype (V0.2.0), developed by Mikael Högqvist

10. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 10 The Semantic Web RDF “Resource description framework”, a W3C recommendation (=standard). RDF is a “semistructured” description of data (examples below) Stellaris uses the RDF/XML syntax Stellaris can use a general xslt to transform XML into RDF (developed by Frank Breitling) Numerous tools and interfaces available from the semantic web community SPARQL “SPARQL Protocol and RDF Query Language”, used to search within the RDF tuples. Results returned in XML or JSON Details are beyond the scope of this talk…

11. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 11 Interoperability Since Stellaris works on a sufficiently abstract layer (i. e. is not bound to specific grid standards) it can serve as an exchange point between different middlewares. It is flexible enough to adopt existing and future schemes. Independend of AstroGrid-D, Stellaris development continues also as a D-Grid project (D-Grid middlewares are GT4, Unicore and gLite) There is a similar development in EGEE (GDSE, …). Exchange?

12. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 12 3. Stellaris Example Robotic Telescopes as information providers to Stellaris

13. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 13 Robotic Telescopes For this use case, Stellaris adopts a custom XML schema, the Robotic Telescope Markup Language (RTML) It stores original RTML and transforms it to RDF/XML Static metadata: Location, filters, instrumentation Dynamic metadata: Observation, Weather, Data “Web 2.0” mashups are used to display the data

14. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 14 RDF @prefix file:. @prefix rdf:. @prefix rtml: rdf:type ; file:owner “Strassmeier, K.”; file:location ; file:filesize "259342"; rtml:Telescope.

15. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 15 SPARQL PREFIX file:. PREFIX rtml:. SELECT ?location ?owner ?telescope FROM <http://stella.aip.de/context/ robotic_telescopes> FROM NAMED WHERE { file:location ?location; file:owner ?owner; rtml:telescope ?telescope. }

16. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 16 Static metadata display Telescope Map Demonstration of Stellaris visualising static metadata using the Google maps web service.

17. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 17 Dynamic metadata display Timeline Demonstration of Stellaris visualising dynamic metadata using the Simile timeline web service.

18. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 18 4. VO Applications How we plan to connect the VO to this

19. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 19 VO implementation So far, Stellaris is used for monitoring of resource, activity and application metadata. The next step is to store scientific metadata. A data detection service will extract metadata and upload it to Stellaris where it will be transformed to RDF (ontology issues?) The service should be automatic or at least very simple for the user (sufficient metadata assumed…)

20. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 20 Web front Once uploaded to Stellaris, data produced on the Grid can be located and monitored (complex queries possible) A interface will be implemented to translate VO compatible URL-queries to Stellaris (SOAP? APIs?) Metadata is to be integrated into the existing visualisation methods. Distinguish between private or public data (include virtual organisations). Start from a specific use case, research how much can be abstracted to general use. Other VO protocol applications: VOspace?

21. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 21 Why Stellaris? / Summary Stellaris is a powerful tool to deal with metadata in the grid context Stellaris offers semantic web features (unlike relational databases). Offers the necessary abstraction layer, but also flexibility. Stellaris can become a central service for both Grid and VO information.

22. www.g-vo.org Iliya Nickelt - Grid and the Virtual Observatory EuroVO DCA Workshop 2008 22 Contributions and Links Stellaris, Visualisations: Mikael Högqvist (AstroGrid-D / ZIB) Robotic Telescopes, Visualisations: Frank Breitling (AstroGrid-D / AIP) General Design: Harry Enke (AstroGrid-D / AIP) GAVO: http://www.g-vo.org AstroGrid-D: http://www.gac-grid.org Running Version of Stellaris: http://is.astrogrid-d.org:25000 Stellaris development: http://stellaris.zib.de