Catalogue and Discovery Services as seen by con terra

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Catalogue and Discovery Services as seen by con
terra

• Kristian Senkler
• http//www.conterra.de

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Requirements on discovery

• Major benefit of catalogue services is
  networking!
• Connect catalogue services to share metadata
  information
• This requires interoperability on both service
  interface and information model level
• Important issues are distributed search
  capabilities of catalogue service specifications
• Concept of application profiles as seen by
  ISO/OGC
• This fits perfectly to the concept of service
  oriented architecture (SOA).
• Loosely coupled service, communicating via
  standardized interfaces
• Catalogue service are key component in any
  spatial data infrastructure

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Distributed search
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Distributed search - concept

• The idea of a distributed search is to start a
  search from a known location and to search
  transitively federated catalogues with the same
  set of attributes.

Client formulates a query
Cumulated resultset
Catalogue searches local and distributes query
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Distributed search - concept

• One single catalogue service is the starting
  point for a distributed search.
• This catalogue acts as a broker service.
• The main focus of a catalogue service broker is
  to integrate one or more federated catalogues in
  its distributed search.
• Benefits/Shortcomings
• Formulate a query once, distribute it to a
  network
• Possible integration of many distinct catalogues
  services
• Specs are not very precise here, or even not
  supporting
• Response time depends on the slowest catalogue
  service

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Distributed search - requirements

• Catalogue service interfaces have to be
  standardized.
• Protocol bindings have to be supported by the
  client.
• Communication has to be standardized
• Query language How has a query to the catalogue
  service has to be formalized?
• Result sets How are the responses of the
  catalogue service formalize (syntactically)?
• Information model What information model does a
  catalogues service support?
• Encoding How is communication payload encoded?

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Catalogue application profiles
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Catalogue application profiles

• A central aspect of OGC CAT 2.0 is the
  possibility to define application profiles.
• ISO TR 10000-11998 describes a general framework
  for functional standardization and defines the
  concept of a profile.
• An application profile
• is based on one of the protocol bindings in the
  base specification (CORBA/IIOP, Z39.50, or the
  HTTP/1.1 protocol bindings)
• may specialise the implementation of base
  interfaces
• is a specialization of the parent protocol
  binding, in that the names of the operations and
  the parameters cannot be changed.

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Catalogue Application Profile General aspects

• An application profile specifies a set of
  functional components that are provided by a
  conforming implementation and binds them to an
  abstract information model (providing one or more
  concrete representations of catalogue content).
• Each representation is an Internet media type
  that conforms to a schema defined using some
  schema language (e.g., ASN.1, XML Schema, RDF
  Schema).
• An application profile specifies the use of an
  application-layer protocol in order to provide a
  structured transfer of information between
  systems.

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Catalogue Application Profile General aspects

• Catalogue application profiles specify
  refinements or extensions that are targeted
  toward specific information communities
• for these communities this application profile
  that represents the standard for conformance.
• The overall goal of profiles is to improve
  interoperability between systems conforming to a
  specific profile. The implication is that an
  implementor does not implement the standard but
  rather configures a client or server to conform
  to one or more profiles.

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Principle of application profiles
Base spec
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Example ISO application profile

• The ISO application profile specifies
• the information model (ISO19115/19119)
• the encodings
• the search terms
• the result sets and its encodings
• the interfaces/operations and protocol
  bindings
• ? this allows to publish, locate and access
  metadata for geospatial data, services, and
  applications
• Current status Latest revision with support for
  ISO 19139 v1.0 as Request for public comments
  at the OGC web site.

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Non OGC CAT 2.0 Space
Other CS
SDIGER
ArcIMS
HTTP/XML?
TCP/IP
OGC CAT 2.0 AP ISO
OGC CAT 2.0 Service Broker
OGC CAT 2.0 AP ISO
HTTP/SOAP
HTTP/SOAP
Client
HTTP/SOAP
HTTP/POST
OGC CAT 2.0 AP ISO
HTTP/POST
OGC CAT 2.0 ebRIM
HTTP/POST
HTTP/POST
OGC CAT 2.0
OGC CAT 2.0
HTTP/POST
OGC CAT 2.0 Space
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Thank you.