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IVOA WebServices

T HE US N ATIONAL V IRTUAL O BSERVATORY. IVOA WebServices. William O’Mullane The Johns Hopkins University. What exactly is a WS ?. FROM http://dev.w3.org/cvsweb/~checkout~/2002/ws/arch/wsa/wd-wsa-arch.html#whatisws

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IVOA WebServices

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  1. THE US NATIONAL VIRTUAL OBSERVATORY IVOA WebServices William O’Mullane The Johns Hopkins University SC4DEVO -Caltech

  2. What exactly is a WS ? FROM http://dev.w3.org/cvsweb/~checkout~/2002/ws/arch/wsa/wd-wsa-arch.html#whatisws [Definition: A Web service is a software system identified by a URI, whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by internet protocols.] Note: Our definition of the term "Web services" does not presuppose the use of SOAP as a packaging format or a processing model. Nor does it presuppose the use of WSDL as a service description language. There are, and will be in the future, plenty of Web services that use raw HTTP as a data transfer protocol and some mutually agreed-upon XML format as the message content. The Web Services *reference architecture* does, however, assume that the higher levels of the Web services protocol stack are built on the foundation of SOAP and WSDL. SC4DEVO -Caltech

  3. Cone and SIAP • CONE • returns all objects within SR or given RA and DEC as XML • has SIZE=0 – returns some metadata as XML • SIAP • returns refs and descriptions of images at POS(RA,DEC) of SIZE(H,W) • has FORMAT=Metadata – returns some metadata But not properly described in a manner which may be used automatically So technically NOT WebServices SC4DEVO -Caltech

  4. WS/SOAP in IVOA and NVO • NVO (and IVOA) find WS a good stepping stone to the GRID without the complexity of GLOBUS etc. • SOAP/WS was not mature enough when CONE/SIAP defined (>2years ago) • General feeling this may be good – but still no agreement to use WS/SOAP extensively e.g. Simple Spectral Access (SSAP) is now being defined in similar manner to SIAP. • NVO and AstroGrid very much in favour of WS. • Platform independent • Tools – language indepentant • WebGrid Services group (G. Rixon IVOA, R. Williams NVO)– starting to define standards SC4DEVO -Caltech

  5. Discover Compute Publish Collaborate VirtualObservatoryArchitecture Portals, User Interfaces, Tools Topcat VOPlot SkyQuery OASIS Mirage DIS Aladin conVOT interfaces to data Registry Layer Data Services Compute Services HTTP Services SOAP Services Grid Servicesstateless, registered & self-describing & persistent, authenticated Semantics (UCD) crossmatch visualization Bulk Access OAI ADS image data mining source detection OpenSkyQuery SIAP, SSAP VOTable FITS, GIF,… Virtual Data Digital LibraryOther registriesXML, DC, METS Workflow (pipelines) Authentication & Authorization Existing Data Centers VOSpace storage services Grid MiddlewareSRB, Globus, OGSASOAP, GridFTP Databases, Persistency, Replication Disks, Tapes, CPUs, Fiber SC4DEVO -Caltech

  6. THE US NATIONAL VIRTUAL OBSERVATORY VO Support Interfaces Working Draft http://www.ivoa.net/internal/IVOA/VOSupportInterfaces-0.2.pdf SC4DEVO -Caltech

  7. getAvailability- Mandetory • Is service alive? • Needs to be more than a ping service should check databases etc. • UpTime • ValidTo – planned downtime SC4DEVO -Caltech

  8. GetRegistration • Method to return VOResource • Make service the owner of the MetaData • Could be used by registry: • Register only the base url • Registry calls MetaData creates the entry • Registry may then refresh periodically SC4DEVO -Caltech

  9. Logging • Will be a large issue – all VO’s will need to report usage • Good to be able to ask service about usage patterns • Implies Logging is done • What is the minimum useful info we need? • Does it need to be secured • Partially secured? SC4DEVO -Caltech

  10. THE US NATIONAL VIRTUAL OBSERVATORY Single Sign OnProposalhttp://www.ivoa.net/twiki/bin/view/IVOA/IvoaGridAndWebServices/IVOA.SingleSignOnProposal SC4DEVO -Caltech

  11. SingleSignOn - Goal • Identification for Access control e.g: • any part where a user stores data or changes the system state; • a minority of archive services where access to the data is restricted; • services that limit use of resources (storage, CPU time, etc.). • Allowing • a user to have one password for the entire VO. • a user to sign in once per session on the VO, not once per use of a service; • services to 'sub-contract' work to other services in a user's name. • Authorization to be done by service provider SC4DEVO -Caltech

  12. SSO – WSSecurity WSSecurity now seems ok Wish to utilize the libraries for SSO in VO So we have: • WSS:Security element in SOAP Header • WSU:Timestamp (signed)-> Uniqueness • Multiple Identity warrants – X509v3 • DS:Signature in SOAP body SC4DEVO -Caltech

  13. SSO- Certificate Authorities Must deal with different warrants: • Long Lived e.g. one year , CA sees ID like passport • Short Lived e.g. one day issued perhaps by a community : CA part of runtime Suggested for VO • Referee e.g. CA endpoint passed in message – service requests warrant from CA Need to experiment – requires trust between CAs SC4DEVO -Caltech

  14. THE US NATIONAL VIRTUAL OBSERVATORY Asynchronous ActivityProposal http://www.ivoa.net/twiki/bin/view/IVOA/IvoaGridAndWebServices/IVOA. AsynchronousActivityProposal SC4DEVO -Caltech

  15. Asynchronous Activity • a major archive query traversing a large DB table; • a data-mining job run from a batch queue; • a workflow with many steps; • a workflow repeated for many data sets. Related : • CASJobs • GAF recently • Open Sky Query SC4DEVO -Caltech

  16. Asynch – What we need. • context: a way of associating a web-service operation with an activity; • a way of getting information about the state of a context; • management of the lifecycle of contexts such that resources are not leaked; • notification by services of changes in contexts, e.g. "job complete". SC4DEVO -Caltech

  17. VOSpace – not yet a proposal Allow interaction of • MyDB • MySpace • SRB • Common WSDL in front of all – not all functionality • Common namespace for all systems SC4DEVO -Caltech

  18. THE US NATIONAL VIRTUAL OBSERVATORY Functioning Web Services Yes its not all paper work ! SC4DEVO -Caltech

  19. WebServices at CDS http://cdsweb.u-strasbg.fr/cdsws.gml • Coordinate Conversions • Aladain Image • Name resolver (NED/SIMBAD/VIZIER) • UCD – Unified Content Descriptor • Vizier Catalogue Metadata SC4DEVO -Caltech

  20. NVO Searchable Registry http://Nvo.stsci.edu/VORegistry • Publication site for astronomical resources: • Individual or Groups of Services, collections, data, etc. • Harvests (collects) resources from other registries • Search Interfaces: simple and complex (as WS) • mixes WS with tradiitonal services • Implements VO standards • IVOA Resource XML schema: astronomical metadata • Dublin core • standard VO Service descriptions and access points • OAI (Open Archive Initiatives) • VO interdisciplinary science gateway • Standard is working draft SC4DEVO -Caltech

  21. SkyNode Cone Search Service Local Publishing Registry Local Publishing Registry Local Publishing Registry Local Publishing Registry Simple Image Access Registry Model Web User search for services STScI/JHU harvest Full Searchable Registry (pull) NCSA publish Vizier Caltech Local Publishing Registry Data Providers search for services Astrogrid Heasarc DIS Data Inventory Service SC4DEVO -Caltech

  22. Galaxy Morphology http://sdssdbs1.stsci.edu/nvo/GalaxyMorph/galmorph.aspx • Uses multiple components • WebService used to hide complete grid computing process • This is a good approach for VO (like Denis showed earlier) • How it works http://nvo.ncsa.uiuc.edu/cgi-bin/SlideShow.cgi SC4DEVO -Caltech

  23. Open Sky Query http://openskyquery.net • Demonstrates ADQL0.7.4 (Working draft) • Demonstrates SkyNode0.7.4 (working Draft) • Creates workflow to cross match multiple distributed catalogs • Open Standards based • SOAP/WSDL • VOTable1.1 SC4DEVO -Caltech

  24. OpenSkyQuery -Architecture March 2004 SC4DEVO -Caltech

  25. Issues • Single Sign On • Security • Certificates • Asynch activity SC4DEVO -Caltech

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