14 Apr 2005 VOEvent workshop1 XML Schema and the VO Registry Matthew J. Graham CACR/Caltech T HE US N ATIONAL V IRTUAL O BSERVATORY

14 Apr 2005 VOEvent workshop2 Overview: the five Ws What is an astronomical resource? How is an astronomical resource described? Where do such descriptions reside? Why are such descriptions needed? When are such descriptions used?

14 Apr 2005 VOEvent workshop3 VOResource: Core Type Title Short name Identifier Curation: –publisher – date –creator– version –contributor– contact Content: –subject– type –description– content level –source– relationship

14 Apr 2005 VOEvent workshop4 VOResource: Extensions Organisation Registry Authority Data Collection: –coverage – format – rights Service: –interface: ParamHTTP, WebService, GLUService –SkyService: TabularSkyService: ConeSearch, SimpleImageAccess, OpenSkyNode –CEAService CEA Application

14 Apr 2005 VOEvent workshop5 Extension models: substitution groups Schema: Instance:

14 Apr 2005 VOEvent workshop6 Extension models: xsi:type Schema: Instance:

14 Apr 2005 VOEvent workshop7 The registry A store for VOResource records (documents) Functionally equivalent to UDDI Records are published into a publishing registry, typically by interactive web form Registries can be harvested via OAI interface: –Identify – ListIdentifiers –ListSets – ListRecords –ListMetadataFormats – GetRecord Records can always be expressed in Dublin Core format Registries can be queried by basic text search and ADQL/XQuery

14 Apr 2005 VOEvent workshop8 Registry implementations RegistryStore typePublishingSearchableHarvestingHandle extensions CaltechNative XMLYes StSCIRelationalYes Partially NCSAFilesystemYes No HEASARCFilesystem?No AstrogridNative XMLYes Yes: CEA GalahadNative XML?Yes Yes: CEA CDSRelational?NoYesNo JVO?No?Yes?Partially: OpenSkyNodeJ + CfA, ESO, ESAC, AusVO, …

14 Apr 2005 VOEvent workshop9 Interoperability problems Namespaces Versioning Incomplete records Wrong records Missing records Validation

14 Apr 2005 VOEvent workshop10 Using schema: registry experiences Validation Code binding: JAXB, Castor –Conflict with W3C XML Schema datatypes –Infinite loops (VOTable) –Marshalling/unmarshalling problems –Performance XSLT –A schema is just an XML document WSDL –Specify the schema?

14 Apr 2005 VOEvent workshop11 Using registries: user experiences Who uses the registry? –Human vs. computer How is the registry used? –Interface functionality Why is the registry used? –Too much metadata?

14 Apr 2005 VOEvent workshop12 Thoughts on VOEvent Schema: –Equivalent of RM document –Straightforward but comprehensive –Core + extensions for specialisations –Based on RTML + STC Ontology –Necessary for querying and filters Registry –VO Registry + subscriber interface