OGC Catalog Services Overview: CS/W, ebRIM, Service Profiles, Metadata & Metametadata OGC - OGF...

OGC Catalog Services Overview:OGC Catalog Services Overview:CS/W, ebRIM, Service Profiles, CS/W, ebRIM, Service Profiles,

Metadata & MetametadataMetadata & MetametadataOGC - OGF Workshop

Joshua Lieberman

Traverse Technologies Inc.

February 2008

©Traverse Technologies. Slide 2

OutlineOutline

• 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


““Catalog” rolesCatalog” roles

• Trader - traditional SOA role– Publish, find, match

• Authority - governance– Standards, vocabularies

• Broker - accessibility– Access, aggregation,

translation

Authority

Broker

Trader

Provider

Consumer


Catalog GoalsCatalog 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


DefinitionsDefinitions

• 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.


Publish-Find-(Bind) Use CasePublish-Find-(Bind) Use Case

GEOSS use case from Nebert, 2007


Distributed Search Use CaseDistributed Search Use Case


Discovery and Binding IssuesDiscovery 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


Catalog service interfacesCatalog service interfaces

• OGC Catalog - CS/W• Z39.50• ISO 23950• UDDI• ebRS• OAI• WFS?• OPeNDAP Query• Echo client partner API’s


Catalog interoperability levelsCatalog 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 19115 / 19139)• Query language• Format / encoding• Registry metadata elements and content

– Status, currency, provenance– Relationships– Classifiers– Statistics

• Trust and authority• Intention and application


Metadata, metamodels, registry metadataMetadata, metamodels, registry metadata

• Metadata– “Data about data”– Application-dependent (“One Man’s metadata…”)

• Metamodel– “Language for describing metadata”

• Registry metadata– “Metadata about metadata”– e.g. Resource identifiers, classifications


Metadata standards, profiles, packagesMetadata standards, profiles, packages

• Data:– ISO 19115 / 19115 part 2 / 19139 - 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 19119 - 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


OGC Catalog layered standardOGC Catalog layered standard

* incoming records representing different metadata standards

are managed within a single information metamodel.

OGC_Service, Discovery, ManagerAbstract 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*


CS/W Base ProfileCS/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


CS/W InterfacesCS/W Interfaces

• OGC Catalog and basic interfaces


CSW Record CSW Record QueryablesQueryables & & PropertiesPropertiesDublin Core element OGC 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.


CS/W ebRIM Metamodel,CS/W ebRIM Metamodel,Basic Package, Extensions, and ProfilesBasic 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).


ebRIM 3.0 High-level ModelebRIM 3.0 High-level Model

• Extrinsic Object


Partial CS/W Record mapping to ebRIMPartial CS/W Record mapping to ebRIM

CSW property name ebRIM information item(s)

dc:identifiera rim:RegistryObject/@id

rim:RegistryObject/rim:ExternalIdentifier/@value

dc:type rim:RegistryObject/@objectType

dc:title rim:RegistryObject/rim:Name

dc:description rim:RegistryObject/rim:Description

dc:subjectb rim:RegistryObject/rim:Slot/rim:ValueList/rim:Value

dc:format rim:ExtrinsicObject/@mimeType

ows:BoundingBoxc rim:RegistryObject/rim:Slot


Catalog 101Catalog 101

• Implementor’s view– CSW with ebRIM management model– Definition of domain resource types– Resource management tools

Your (Meta) resources Extrinsic Objects

Your IdentifiersResource IDs

Relationships Associations

Categories Classifications

QueryablesSlots

• ebRIM Nomenclature


Significant Queryables and ReturnablesSignificant 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


DiscussionDiscussion

• 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 person’s data is another’s 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?

OGC Catalog Services Overview: CS/W, ebRIM, Service Profiles, Metadata & Metametadata OGC - OGF...

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