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| Titel |
GI-cat extensions for OGC 06-131 and OGC 07-038 support |
| VerfasserIn |
E. Boldrini, F. Papeschi, P. Mazzetti, L. Bigagli, F. Vitale, S. Nativi |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022663
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| Zusammenfassung |
| In this presentation we discuss the extensions developed in order to enable GI-cat to support
the OGC CSW ebRIM application profile and its extension packages: EO (Earth Observation)
and CIM (Cataloging of ISO Metadata).
In an Service-Oriented Architecture (SOA) framework, GI-cat implements a distributed
catalog service providing advanced capabilities, such as: caching, brokering and
mediation functionalities. GI-cat applies a distributed approach, being able to distribute
queries to the remote service providers of interest in an asynchronous style, and
notifies the status of the queries to the caller implementing an incremental feedback
mechanism. GI-cat functionalities were made available through two standard catalog
interfaces: the OGC CSW ISO and CSW Core Application Profiles. The presented
extensions will add two new and standard interfaces: the CSW ebRIM CIM and
EO interfaces. GI-cat is able to interface a multiplicity of discovery and access
services serving heterogeneous Earth and Space Sciences resources. They include
international standards like the OGC Web Services – i.e. OGC CSW, WCS, WFS and
WMS, as well as interoperability arrangements (i.e. community standards) such as:
UNIDATA THREDDS/OPeNDAP, SeaDataNet CDI (Common Data Index), GBIF
(Global Biodiversity Information Facility) services, and SibESS-C infrastructure
services.
The GI-cat distributed catalog service has been successfully deployed and experimented
in the framework of different projects and initiative, including the SeaDataNet FP7 project,
GEOSS IP3 (Interoperability Process Pilot Project) and GEOSS AIP-2 (Architectural
Implementation Project – Phase 2).
Commonly, a catalog application profile and/or extension package introduces a specific
data model. Hence, an important objective of the developed expansion module is to define
and implement an effective and flexible strategy to support the new data model, in the
context of the existing information model – i.e the GI-cat data model. Besides,
the expansion module is required to implement the new interface defined by the
application profile/extension-package. Usually, this implies the definition of a new system
loosely-coupled components – e.g. a mediator for the new interface. Several different
extension strategies were identified and analyzed:
Model Mapping strategy: to define a mapping between the new data model
entities and the internal GI-cat ones.
Model Extension strategy: To extend the GI-cat internal data model, adding
extension points which are the roots of the new concepts introduced by the
profile/extension specification. Where possible, suitable extension points are
useful to preserve the existing code and minimize the impact of the new concepts
on the internal model.
Model Modification strategy: To modify the GI-cat internal data model
accommodating the new concepts introduced by the profile/extension
specification. Generally, this option does not preserve the existing code changing
the internal model in a structural way.
Depending on the data model to be supported an approach may be preferable to another.
To implement the CIM extension package, the full mapping strategy (i.e. Mapping strategy)
was conveniently used. While, to support the EO extension package a two step strategy was
needed: GI-cat data model was extended to accommodate a set of some new concepts
introduced by the EO data model (i.e. Model Extension strategy), while the others were
mapped to the existing GI-cat internal model to assure basic interoperability (i.e. Model
Mapping strategy).
This work was developed in the context of ESA HMA project, whose main objective is to
involve the stakeholders, namely National space agencies, satellite or mission owners and
operators, in an harmonization and standardization process of their ground segment services
and related interfaces. |
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