OPeNDAPOGC Gateway to support Regional IOOS interoperability - PowerPoint PPT Presentation

Title: OPeNDAPOGC Gateway to support Regional IOOS interoperability


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OPeNDAP/OGC Gateway to support Regional IOOS
interoperability

• Opportunity to implement an interoperability
  approach presented by the OPeNDAP community
  Semantic Mapping Framework, developed by Benno
  Blumenthal _at_ Columbias IRI.
• Using Namespaces in DAP attributes to explicitly
  label which convention it belongs to, and
  multiple (partially redundent) conventions can be
  carried by the transport mechanism.
• Take advantage of newer rule-based systems for
  writing down translations that could simplify
  maintaining and testing of translations
• Resource Description Language (RDF) and its
  associated semantic conventions such as Web
  Ontology Language (OWL) provide a way of writing
  down metadata structures and such mappings.
• The basic strategy in RDF/OWL is that instead of
  creating a super-schema, you just have all the
  metadata in multiple namespaces attached to the
  data, and standard rules/engines for creating
  metadata in one scheme from metadata in another
  scheme. And if a standard engine does not work,
  you can always write a specialized one until the
  standard ones becomes more complete.

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Carrying Semantics in the DAP
Precisely stating which attributes belong to
which conventions makes understanding the entire
set of attributes much easier when multiple
conventions are used to add semantics to DAP
variables. Slight change in conventional usage
allows semantics to be carried in the current
version of the DAP. Extend usage of Conventions
attribute to allow namespace specification,
.i.e. use strings of the form nsURI, .e.g.
cfatthttp//iridl.columbia.edu/ontologies/cf-att.
owl Then use namespace abbreviation in
attributes, .e.g. cfattstandard _name Use URL
attribute types for URIs We should additionally
specify what the proper URI for each entity in a
DAP data set should be, .i.e., dods_urlvariable_n
ame or urnopendapvariable_name so that DAP
variables can be consistently referred to by
RDF.OWL and/or XML files. Establishing URIs for
the elements within an OPeNDAP data set means
that outside documents/software can refer to
those elements and make semantic statements about
them. This allows use semantic translation, where
an outside program can translate the use
semantics of a variable into different
conventions, e.g. CF or OpenGIS or GRIB or any of
the many lesser-known systems for adding some
metadata to data.
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Explicitly recognizing that the URL type should
be used to refer to standard concepts, while not
literally a change to OPeNDAP, provides a way to
transport semantics external to OPeNDAP.
ltsosobservedProperty xlinkhref"http//marineme
tadata.org/cfsea_water_temperature"/gt
ltsosunits href"urnOGCunitdegree" /gt
ltsosfeatureOfInterest xlinkhref"urnmmi.featur
ebodyOfWater" /gt can be transported (adding
some more attributes)
sst URL sosobservedProperty
"http//marinemetadata.org/cfsea_surface_temperat
ure" URL sosunits "urnOGCunitdegree"
URL sosfeatureOfInterest "urnmmi.featurebody
OfWater" String cfattunits
"degree_Celsius" String cfattlong_name
"sea surface temperature" String
cfattstandard_name "sea_surface_temperature"
URL termisDescribedBy "http//iridl.ldeo.columb
ia.edu/ontologies/iridl.owlNOAA",
"http//sweet.jpl.nasa.gov/ontology/data_center.ow
lNational_Oceanic_and_Atmospheric_Administration"
, "http//marinemetadata.org/2005/08/gcmd
-keywOceans" URL iridlhasDocumentation
"http//iridl.ldeo.columbia.edu/ontologies/Referen
ceList.owlReynolds_Smith1994" NC_GLOBAL
String Conventions "soshttp//www.opengis.net/
sos/0", "cfatthttp//iridl.ldeo.columbia
.edu/ontologies/cf-att.owl",
"iridlhttp//iridl.ldeo.columbia.edu/ontologies/i
ridl.owl", "termhttp//iridl.ldeo.colum
bia.edu/ontologies/iriterms.owl"
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Server Architecture (Hyrax)
DAP2
BES Commands
THREDDS
HTML
OGC WxS
XML encapsulated object
Optional THREDDS Catalogs
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Server Architecture (Hyrax)
DAP2
BES Commands
THREDDS
HTML
OGC WxS

• Module-based Architecture where separate modules
  support different application-level protocols.
• Handles inbound requests
• Determines how a response should be built.
• Communicates with BES using a stateful,
  conversational, protocol.
• May ask BES to access different data sources,
  return information on filesystem, or return
  different (DAP) responses.

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Server Architecture (Hyrax)
XML encapsulated object

• Module-based Architecture, where run-time
  loadable modules are used to build response
  objects.
• Format Handlers
• Write data into DAP response objects
• Response Handlers
• Read data from DAP response objects
• Ancillary Information Service (AIS) - DDX

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OPeNDAP/OGC Gateway to support Regional IOOS
interoperability

• Kickoff Meeting
• Fall AGU Meeting - Dec. 2007
• Generating Use Cases
• Driven by OGC Interface Specification
• Developing OWL descriptions for DAP, CF, WxS
• Module for DDX -gt RDF, and RDF -gt DDX
• Refining the design, focus on modularization for
  development and test as standalone elements.
• DM Issues
• Interface Specification Revision to support
• Aggregating file-based collections