AGROVOC in SKOS

Tom Baker13 April 2010

My “hats”

• As connsultant– Completing “autoevaluation” of FAO standardization activities,

including AGROVOC– Will work with FAO team on modeling aspects of migration to SKOS

• Other roles– CIO , Dublin Core Metadata Initiative– Until August 2009, co-chaired W3C Semantic Web Deployment

Working Group, which standardized SKOS– Currently organizing W3C Library Linked Data Incubator Group

noun

lexicalization

domain concept

maize

has_synonymhas_translation

means 12332corn (en)maïs (fr)

corn

has_synonymmeans 12332

maize (en)

has_lexicalization

has_lexicalization

sub_class_of

has_synonym

AGROVOC metamodel 2010 (simplified)

12332rdf:type

sub_class_of

sub_class_of

sub_class_ofsub_class_of

rdf:type

Concept 6211(Products)

Concept 8171:(Plant products)

Concept 1474:(Cereals)

Concept 12332:(Maize)

8171

1474

12332

skosxl:altLabel

skosxl:prefLabel

skos:broader

SKOS Label

skos:broader

SKOSConcept

rdf:type

rdf:type

6211skos:broader

AgrovocConceptScheme

skos:topConceptOfskos:inScheme

SKOSConceptScheme

rdf:type

rdf:type

:bar

:foo

“corn”

“maize”

skosxl:literalForm

skosxl:literalForm

rdf:type

rdf:type

rdf:type

AGROVOC SKOS model (proposed)

“maize”has_synonymhas_translation

“corn” (en)“maïs” (fr)

“corn”has_synonym “maize” (en)

altLabel

prefLabel

broader

has_synonym

AGROVOC metamodel for brochures and interfaces

broader

broader

Concept 6211:Products

Concept 8171:Plant products

Concept 1474:Cereals

Concept 12332:Maize

Rationale for migrating to SKOS

• Abandons unique FAO vocabulary model metamodel) in favor of highly standardized model– Anticipated tool and software library support, so can push Workbench

software development further out into the community– When converted to a SKOS basis, Workbench would be interesting to

hundreds of other users for creating SKOS Concept Schemes• SKOS-2009 supports Lexicalizations (Labels) as resources

SKOS-XL• SKOS-XL extension: labels as resources• Just 16 triples:

– skosxl:Label owl:disjointWith skos:ConceptScheme. skosxl:Label owl:disjointWith skos:Concept.skosxl:Label owl:disjointWith skos:Collection.skosxl:Label rdf:type owl:Class. skosxl:altLabel rdf:type owl:ObjectProperty. skosxl:altLabel rdfs:range skosxl:Label. skosxl:hiddenLabel rdf:type owl:ObjectProperty. skosxl:hiddenLabel rdfs:range skosxl:Label. skosxl:labelRelation rdf:type owl:ObjectProperty.skosxl:labelRelation rdf:type owl:SymmetricProperty. skosxl:labelRelation rdfs:domain skosxl:Label. skosxl:labelRelation rdfs:range skosxl:Label. skosxl:literalForm rdf:type owl:DatatypeProperty. skosxl:literalForm rdfs:domain skosxl:Label. skosxl:prefLabel rdf:type owl:ObjectProperty. skosxl:prefLabel rdfs:range skosxl:Label.

How AGROVOC is actually used

• Highly engineered ontologies have not materialized– Agrovoc concepts for simpler purposes – portal navigation, learning

(Agropedia), resource discovery– Several projects set out to build high-engineered ontologies and failed

• AGROVOC concepts function as quarry of building blocks for constructing local concept schemes

Minimal ontological commitment

• An ontology should require the minimal ontological commitment sufficient to support the intended knowledge sharing activities. An ontology should make as few claims as possible about the world being modeled, allowing the parties committed to the ontology freedom to specialize and instantiate the ontology as needed. Since ontological commitment is based on consistent use of vocabulary, ontological commitment can be minimized by specifying the weakest theory (allowing the most models) and defining only those terms that are essential to the communication of knowledge consistent with that theory. (Gruber 1994)

Ontologically weaker = better!

• Agrovoc is large, diverse, and multi-lingual.– Does not reflect a strong “point of view”, which is prerequisite for advanced

ontological reasoning. – Better to model Agrovoc entities with a weaker ontological commitment (SKOS

concepts) than with a strong ontological commitment (OWL classes).– Ontologically weaker definitions more apprropriate to multiple ways they are

actually used• Reusers of OWL classes downstream would inherit ontological baggage

of OWL sub-class relationships• SKOS Concepts does not preclude use of refined relationships (e.g., can

also be transitive, inverse, symmetric)• SKOS concepts can be upgraded to OWL classes in specialized, local

ontologies• SKOS concepts are easier to teach (capacity-building)

Consequences for Workbench

• Short term: no impact on software IF– User Interface of Workbench is consistent with AGROVOC/SKOS

metamodel– Data of AGROVOC/SKOS representation can be exposed –

correctly – as Linked Data• Offer Ntriples, RDF/XML, and Turtle representations for download• Note: iif necessary, n short term, could be simplified version of data!

• Long term– Ongoing software development will be more sustainable if it can

leverage generic SKOS tools , interfaces, and software libraries under development

Solves problem of instances

• Currently, in AGROVOC/OWL-2006, “Ghana” is an OWL class• There is nothing in SKOS data model that prevents an Instance from

being considered a SKOS Concept• Distinction between classes and instances is hard to teach (Gudrun)• NeOn Project difficulties

– Upgrading legacy thesauri (e.g., AFSA) to class hierarchies in order to map to AGROVOC – ripple effect of initial ontological overcommitment

– Is a species of fish a “class” (and the actual individual fish are instances) or “instances” (as in statistical data)?

– "The domain of interpretation of fisheries can contain entities as well as types of entities, and distinguishing them in a logically sound way would require a huge amount of fishery experts time, and only after they are organized in a team sided by ontology designers and are taught design tools adequately" (Caracciolo)

WHAT TRIPLES ACTUALLY SAY

AGROVOC/OWL-2006

• 2,113,264 triples

Concept to label

• 233800 hasLexicalization 99741 hasMainLabel

Instance to Literal

• 107 instance-comment-literal 33 instance-first-literal 103745 instance-hasDateCreated-literal 4011 instance-hasDateLastUpdated-literal 22 instance-hasEditorialNote-literal 3268 instance-hasScopeNote-literal 103701 instance-hasStatus-literal 6362 instance-hasTermType-literal 99735 instance-hascodeagrovoc-literal 155 instance-hascodeiso3country-literal 739 instance-isPartOfSubvocabulary-literal 100010 instance-label-literal 1 instance-versionInfo-literal

Instance rdf:type other

• 3972 instance-rdftype-class 38 instance-rdftype-definition 99735 instance-rdftype-noun

AOS predicates

• 43384 aos-hasSynonym 30461 aos-other 1167435 hasTranslation

RDF and OWL predicates

• 4 owl-oneOf 4 owl-unionOf 193 owl-inverseOf 12 rdf-first 45 rdf-rest 41 rdfs-domain 38 rdfs-range 216 rdfs-subPropertyOf 38 rdftype 273 rdftype-Property 3996 rdftype-owlClass – not more?? 3976 subClassOf 3972 subClassOf-owl-thing

MESSAGE AND INTERFACE

“Agrovoc Concept Scheme”

• “Agrovoc Concept Server” is intended to refer to the quarry of concepts that users can mine as a foundation for building their own ontologies. However, “Server” evokes machines, applications, APIs…

• Why not “Agrovoc Concept Scheme”? (Same acronyms.)– SKOS concepts are designed to be reused and recombined in multiple

concept schemes – perfect fit– Possibly de-emphasize the word “ontology”

• In terms of capacity building, OWL is more difficult to teach than SKOS

FORM OF URIS

Form URIs and publish Linked Data

• Promote Agrovoc URIs for linked data – print on teeshirts?– http://aims.fao.org/aos/v1.0/c_1939: with slash?– http://aims.fao.org/aos/agrovoc#c_1939: with hash?– http://aims.fao.org/aos/c_1939: minus version number?– http://aims.fao.org/agrovoc/c_1939: minus aos?– Under own domain or using purl.org?

• How to publish– RDF and HTML representations with content negotiation?– Publish embedding RDF representation within HTML page using RDFa?

Agrovoc mappings

• Guus Schreiber (paraphrased)– Every vocabulary has its own perspective. You can't just merge them. – But you can use vocabularies jointly by defining a limited set of links –

“vocabulary alignment”.– Don't recreate – re-use, enrich, and align.– Beware of ontological over-commitment.– Specifying a data model in OWL does not make it an ontology.

• Suggest emphasis on mappings, expressed as linked data– Increases effective “range” of Agrovoc concepts– Suggests new impact indicators based on numbers of resources

findable via Agrovoc concepts – both directly and indirectly, through mapping links to CABI, etc.

“maize”has_synonymhas_translation

“corn” (en)“maïs” (fr)

“corn”has_synonym “maize” (en)

altLabel

prefLabel

broader

has_synonym

AGROVOC Concept Scheme?

broader

broader

Concept 6211:Products

Concept 8171:Plant products

Concept 1474:Cereals

Concept 12332:Maize

AGROVOC model (2003)

Plant products(concept)

Cereals(concept)

Plant products (lexicalization)

Cereals(lexicalization) Maize (concept)

Maize (lexicalization)

“Maize” (string)

“Corn” (string)

“Mais” (string, French)

Circa 2005 – String entity in light blue

c_apple

apple

APL

pomme

c_fruit

translation

PMM

red fruitsynonym

acronym

aple

spelling variant

The modeling Distinction betweenLexicalization and String

noun

lexicalization

domain concept

means

has_lexicalization

maize

has_synonymhas_translation

means 12332corn (en)maïs (fr)

corn

has_synonymmeans 12332

maize (en)

sub_class_of

8171

1474

12332

meansmeans

has_lexicalization

has_lexicalization

sub_class_of

has_synonym

Agrovoc OWL modelas presented in 2005

noun

lexicalization

domain concept

maize

has_synonymhas_translation

means 12332corn (en)maïs (fr)

corn

has_synonymmeans 12332

maize (en)

8171

1474

12332

has_lexicalizationhas_lexicalization

sub_class_of

has_synonym

Agrovoc OWL model – ver 1

12332rdf:type

sub_class_of6211

sub_class_of

sub_class_ofsub_class_of

rdf:type

noun

lexicalization

domain concept

maize

has_synonymhas_translation

means 12332corn (en)maïs (fr)

corn

has_synonymmeans 12332

maize (en)

has_lexicalization

has_lexicalization

sub_class_of

has_synonym

Agrovoc OWL model – ver 2

12332rdf:type

sub_class_of

sub_class_of

sub_class_ofsub_class_of

rdf:type

Concept 6211(Products)

Concept 8171:(Plant products)

Concept 1474:(Cereals)

Concept 12332:(Maize)

“maize”has_synonymhas_translation

“corn” (en)“maïs” (fr)

“corn”has_synonym “maize” (en)

has_lexicalization

has_lexicalization

broader

has_synonym

Agrovoc modelproposed for brochure

broader

broader

Concept 6211:Products

Concept 8171:Plant products

Concept 1474:Cereals

Concept 12332:Maize

:bar

has_synonymhas_translation

skos:literalForm “maize”:foomaïs (fr)

:foo

has_synonymskos:literalForm “corn”

:bar

8171

1474

12332

skosxl:altLabel

skosxl:prefLabel

skos:broader

has_synonym

SKOS Label

AGROVOC in SKOS – ver 1

skos:broaderSKOSConcept

rdf:type

rdf:type

6211skos:broader

AgrovocConceptScheme

skos:topConceptOfskos:inScheme

SKOSConceptScheme

rdf:type

rdf:type

8171

1474

12332

skosxl:altLabel

skosxl:prefLabel

skos:broader

SKOS Label

skos:broader

SKOSConcept

rdf:type

rdf:type

6211skos:broader

AgrovocConceptScheme

skos:topConceptOfskos:inScheme

SKOSConceptScheme

rdf:type

rdf:type

:bar

:foo

“corn”

“maize”

skosxl:literalForm

skosxl:literalForm

rdf:type

rdf:type

rdf:type

AGROVOC OWL model – used in report