OGC Catalog Services Overview: CS/W, ebRIM, Service Profiles, Metadata & Metametadata OGC - OGF Workshop Joshua Lieberman Traverse Technologies Inc. February 2008

©Traverse Technologies. Slide 2 Outline Catalog roles and goals Definitions: catalog, registry, repository, archive, clearinghouse, portal Catalog use cases Catalog service interfaces Catalog interoperability Metadata, metamodels, registry metadata Metadata standards, profiles, packages Catalogs and grids

©Traverse Technologies. Slide 3 Catalog roles Trader - traditional SOA role –Publish, find, match Authority - governance –Standards, vocabularies Broker - accessibility –Access, aggregation, translation Authority Broker Trader Provider Consumer

©Traverse Technologies. Slide 4 Catalog Goals System-wide discovery –Discovery of data and service (computing, workflow) resources –Discovery of other discovery resources –Management of discovery metadata –Added value to resource descriptions (classify, associate) System governance –Data types and formats –Service interfaces –Vocabularies –Classification / tagging schemes System broker / mediation –Perform ordering –Mediate data and service heterogeneities –Match services and/or resources to each other Power portals and other discovery applications –Query indexes –Metadata mining and dictionaries –User profiles

©Traverse Technologies. Slide 5 Definitions Catalog –Service / component / arrangement for discovering resources through metadata Registry –Service / component / arrangement for managing catalogs and registers through metadata about metadata Repository –Persistence / storage function particularly for metadata resources (access by ID) Archive –Function/service/capability for managing the persistence of data resources (lifecycle, lineage, provenance) Clearinghouse –Broker for access to capabilities, particularly metadata resources CS/W –Catalog Service for the Web - an OGC implementation specification with an HTTP protocol binding and base metadata profile. Based on the (abstract) OGC Catalog Specification, version 2 ebRIM –e-business Registry Information Model - an OASIS information model for documenting and managing metadata objects in a Web registry. Paired with ebRS - an interface specification for a combined registry - repository (reg-rep) service.

©Traverse Technologies. Slide 6 Publish-Find-(Bind) Use Case GEOSS use case from Nebert, 2007

©Traverse Technologies. Slide 7 Distributed Search Use Case

©Traverse Technologies. Slide 8 Discovery and Binding Issues How much information is enough, how much is too much for a catalog? Metalevels –Community –Capability –Service –Collection –Item –Item component –Process model / capabilities Currency –Distributed search versus periodic harvest of remote metadata –Status metadata versus status query of remote service

©Traverse Technologies. Slide 9 Catalog service interfaces OGC Catalog - CS/W Z39.50 ISO UDDI ebRS OAI WFS? OPeNDAP Query Echo client partner APIs

©Traverse Technologies. Slide 10 Catalog interoperability levels Service interface / protocol –Messages, interaction styles Metamodel –Text (e.g. search engines) –Record (traditional catalog) –Graph (e.g. knowledgebase) –Other object model Metadata model (e.g. ISO / 19139) Query language Format / encoding Registry metadata elements and content –Status, currency, provenance –Relationships –Classifiers –Statistics Trust and authority Intention and application

©Traverse Technologies. Slide 11 Metadata, metamodels, registry metadata Metadata –Data about data –Application-dependent (One Mans metadata…) Metamodel –Language for describing metadata Registry metadata –Metadata about metadata –e.g. Resource identifiers, classifications

©Traverse Technologies. Slide 12 Metadata standards, profiles, packages Data: –ISO / part 2 / descriptions of geodata, datasets, imagery –FGDC Content Standard - descriptions of geodatasets –FGDC Biological Data Profile - descriptions of biological data –Darwin Core - descriptions of biological data –DDMS - descriptions of feature types and schemas –ABCD - descriptions of species datasets –EO-HMA - descriptions of earth observation products –Dublin Core - universal descriptions of resources Services –OWS - descriptions of OGC Web services –ISO ISO descriptions of geospatial services –WSDL - definitions of Web services –WSRF - descriptions of Web services –OWL-S - OWL definitions of services –SAWSDL - WSDL with Semantic Annotations

©Traverse Technologies. Slide 13 OGC Catalog layered standard * incoming records representing different metadata standards are managed within a single information metamodel. OGC_Service, Discovery, Manager Abstract Interfaces and Operations HTTP (Catalog Service / Web) Protocol Bindings (information agnostic) CS/W Common, ebRIM Resource Information Model Ingest, Classify, Present, Order, etc. Value-added Application Services Services, Datasets, Schemas, etc. Registry Information Model*

©Traverse Technologies. Slide 14 CS/W Base Profile Discovery manager interface - GetCapabilities, GetRecords, DescribeRecords Publication manager interface - Harvest, Transaction CSWRecord (record-oriented) metamodel Consists mainly of Dublin Core properties OGC Core queryables Brief, summary, full result sets Special attributes: –[WGS84]BoundingBox –AnyText

©Traverse Technologies. Slide 15 CS/W Interfaces OGC Catalog and basic interfaces

©Traverse Technologies. Slide 16 CSW Record Queryables & Properties Dublin Core elementOGC queryables Definition title Title A name given to the resource. Also known as Name. creator An entity primarily responsible for making the content of the resource. subject Subject A topic of the content of the resource. This is a place where a Topic Category or other taxonomy could be applied. description Abstract An account of the content of the resource. This is also known as the Abstract in other aspects of OGC, FGDC, and ISO metadata. publisher An entity responsible for making the resource available. This would equate to the Distributor in ISO and FGDC metadata. contributor An entity responsible for making contributions to the content of the resource. date Modified The date of a creation or update event of the catalogue record. type Type The nature or genre of the content of the resource. format Format The physical or digital manifestation of the resource. identifier Identifier A unique reference to the record within the catalogue. source Source A reference to a resource from which the present resource is derived. language A language of the intellectual content of the catalogue record. relation Association The name of the relationship that exists between the resource described by this record and a related resource referenced using the Source or dc:source property. coverage BoundingBox The spatial extent or scope of the content of the resource. rights Information about rights held in and over the resource.

©Traverse Technologies. Slide 17 CS/W ebRIM Metamodel, Basic Package, Extensions, and Profiles ebRIM provides specialized record types which represent registry metadata or a metamodel for describing metadata. Basic package is a set of ebRIM records and record types to support OWS (OGC Web Services) metadata. Extension packages (e.g. SWE, EO, ISO) add ebRIM records to model the metadata of other resource domains or support particular metadata standards. Profiles match extension packages with metadata practice to enhance interoperability. If metadata (e.g. harvested service capabilities) are not ingested into ebRIM data objects the same way in different services, they cannot be queried by a client (or process distributed queries) in the same way, and so catalog services are no longer interoperable (that is, interchangeable).

©Traverse Technologies. Slide 18 ebRIM 3.0 High-level Model Extrinsic Object

©Traverse Technologies. Slide 19 Partial CS/W Record mapping to ebRIM CSW property nameebRIM information item(s) dc:identifier a dc:titlerim:RegistryObject/rim:Name dc:descriptionrim:RegistryObject/rim:Description dc:subject b rim:RegistryObject/rim:Slot/rim:ValueList/rim:Value ows:BoundingBox c rim:RegistryObject/rim:Slot

©Traverse Technologies. Slide 20 Catalog 101 Implementors view –CSW with ebRIM management model –Definition of domain resource types –Resource management tools Your (Meta) resources Extrinsic Objects Your Identifiers Resource IDs RelationshipsAssociations Categories Classifications Queryables Slots ebRIM Nomenclature

©Traverse Technologies. Slide 21 Significant Queryables and Returnables Queryables –Time period of data validity –Time period of collection –Resource type –Phenomenon represented –Full text –Geographic Extent –Topic categories / ISO terms –Title –Creator –Organization –Language –Scale / resolution –Metalevel –Classification –Processed state Returnables –Identifier –Resource locator –Quality –Description –Abstract –Copyright / Use constraints –Source –Last update

©Traverse Technologies. Slide 22 Discussion Record orientation (including relationships) is a clear user / client paradigm but hard to maintain and limited for complex metadata relationships. A registry metamodel makes catalogs easier and more flexible to maintain, but should its complexities be exposed to all /most users / clients? What is the difference between a catalog service and a feature service? Geospatial metadata can indeed be encoded as features, so a WFS can function as a rudimentary (possibly very fast) catalog, but is generally unable to provide more catalog-specific, metadata-specific functions. What is the most appropriate level of detail and currency for a catalog versus other services? Should various catalog roles (discovery, broker, authority, repository) be combined in one service or are they better separated? If a catalog adds value (identity, authority, association, classification, translation, …), where does this information come from and who maintains it? In what applications are catalogs and their holdings to be treated as more discoverable services with content (I.e. one persons data is anothers metadata) Relevance for grids and grid services? Can / should a catalog function as a grid map? Can (descriptions of ) grid capabilities and processes be modeled effectively in ebRIM? What is the overlap between a catalog broker and a workflow manager?