IRI Data Library Faceted Search: an example of

• RDF-based faceted search for climate data

• Drawing on multiple ontologies to build an application

• Using inference to connect ontologies describing different parts of the framework

http://iridl.ldeo.columbia.edu/ontologies/

Faceted Searchhttp://iridl.ldeo.columbia.edu/ontologies/query2.pl?...

Distinctive Features of the search

• Search terms are interrelated

• terms that describe the set of returns are displayed (spanning and not)

• Returned items also have structure (sub-items and superseded items are not shown)

Architectural Features of the search

• Interface is generated from a set of Terms connected to a set of Items

• Multiple search structures possible• Multiple languages possible• Search structure is kept in the database, not in

the code

http://iridl.ldeo.columbia.edu/ontologies/query2.pl

Search Interface as Multiple Ontologies

Search Interface

Users

Datasets

Search Ontology

Dataset Ontology

Additional Semantics

Ontology Types

• Attribute Ontology (e.g. Dataset)

• Object Ontology (essential for crosswalk)

• Term Ontology (e.g. search ontology)

Attribute Ontology

• Subjects are the only type-object

• Predicates are “attributes”

• Objects are datatype

• Isomorphic to simple data tables

• Isomorphic to netcdf attributes of datasets

• Some faceted browsers: predicate = facet

Object Ontology

• Objects are object-type• Isomorphic to “belongs to”• Isomorphic to multiple data tables connected by

keys• Express the concept behind netcdf attributes

which name variables • Concepts as objects can be cross-walked• Concepts as object can be interrelated

Example: controlled vocabulary

{variable} cfatt:standard_name {“string”}

Where string has to belong to a list of possibilities.

{variable} cfobj:standard_name {stdnam}

Where stdnam is an individual of the class cfobj:StandardName

Example: controlled vocabulary

Bi-direction crosswalk between the two is somewhat trivial, which means all my objects will have both

cfatt:standard_name

and

cfobj:standard_name

Example: controlled vocabulary

If I am writing software to read/write netcdf files, I use the cfatt ontology and in particular cfatt:standard_name

If I am making connections/cross-walks to other variable naming standards, I use

cfobj:standard_name

Term Ontology

Concepts as individuals

Simple Knowledge Organization System (SKOS) is a prime example

The ontology used here is slightly different than SKOS: facets are classes of terms rather than being top_concepts

Nuanced tagging

Concepts as objects can be interrelated: specific terms imply broader terms

Object ends up being tagging with terms ranging from general to specific.

Search can then be nuancedtagging can proceed in absence of perfect

information

Faceted Search Explicated

Search Interface

• Items (datasets/maps)

• Terms

• Facets

• Taxa

Search Interface Semantic API

{item} dc:title dc:description rss:link iridl:icon dcterm:isPartOf {item2} dcterm:isReplacedBy {item2}

{item} trm:isDescribedBy {term}

{term} a {facet} of {taxa} of {trm:Term},{facet} a {trm:Facet}, {taxa} a {trm:Taxa},{term} trm:directlyImplies {term2}

Faceted Search w/Querieshttp://iridl.ldeo.columbia.edu/ontologies/query2.pl?...

RDF Architecture

RDF

RDF RDF

RDF

RDF RDF

RDF

RDF RDF

RDF

RDF

RDF RDF

RDF

RDF RDF

Virtual (derived) RDF

queries queries queries

Data ServersOntologies

MMI

JPL

StandardsOrganizations

Start Point

RDF Crawler

RDFS SemanticsOwl SemanticsSWRL Rules

SeRQL CONSTRUCT

Search Queries

LocationCanonicalizer

TimeCanonicalizer

Sesame

Search Interface

bibliography

IRI RDF Architecture

Cast of Characters

NC – netcdf data file format

CF – Climate and Forecast metadata convention for netcdf

SWEET - Semantic Web for Earth and Environmental Terminology (OWL Ontology)

IRIDL – IRI Data Library

CF attributes

SWEET Ontologies(OWL)

Search Terms

CF Standard Names(RDF object)

IRIDL Terms

NC basic attributes

IRIDLattributes/objects

SWEET as Terms

CF Standard NamesAs Terms

Gazetteer Terms

CF data objects

Location

See Also

• http://iridl.ldeo.columbia.edu/ontologies/

• http://iri.columbia.edu/~benno/Talks/AGU2007Poster.pdf