Mapping OBO to OWL 1.1 Christine Golbreich & Ian Horrocks

OBO and OWL OBO: De facto standard ontology language Large user community –Mainly in life sciences Extensive library of ontologies High quality tools Informally specified syntax and semantics OWL: W3C standard ontology language Large user community –Many in life sciences Extensive library of ontologies High quality tools Formally specified syntax and semantics

OWL and OBO OWL: W3C standard ontology language Large user community –Many in life sciences Extensive library of ontologies High quality tools Formally specified syntax and semantics OBO: De facto standard ontology language Large user community –Mainly in life sciences Extensive library of ontologies High quality tools Informally specified syntax and semantics

OBO at a Glance Ontology consists of a set of stanzas (frames) Term stanzas define terms (classes), e.g. [Term] id: GO: name: oocyte growth is_a: GO: ! cell growth relationship: part_of GO: ! oocyte morphogenesis intersection_of: GO: ! growth intersection_of: has_central_participant CL:

OBO at a Glance Ontology consists of a set of stanzas (frames) Typedef stanzas define relationships (properties), e.g. [Typedef] id: propreo:is_described_by domain: propreo:chemical_entity range: __Description177

OBO at a Glance Ontology consists of a set of stanzas (frames) Instance stanzas define instances (individuals), e.g. [Instance] id: propreo:water_molecule instance_of: propreo:inorganic_solvent_molecule property_value: propreo:is_described_by propreo:CHEBI_15377

OBO and OWL OBO $ OWL interoperability would be useful –Sharing ontologies –Extending tool sets Establishing exact relationship is not easy –OBO syntax not formally specified, e.g.: The intersection_of tag “indicates that this term represents the intersection of several other terms. The value is either a term id, or a relationship type id, a space, and a term id. [...]”

OBO and OWL OBO $ OWL interoperability would be useful –Sharing ontologies –Extending tool sets Establishing exact relationship is not easy –OBO semantics not formally specified, e.g.: The relationship tag “describes a typed relationship between this term and another term. [...] cardinality constraints specify the number of relationships of a given type that may be defined for instances of this term [...]”

Proposed Solution Formalise OBO syntax using BNF grammar, e.g.: The intersection_of tag “indicates that this term represents the intersection of several other terms. The value is either a term id, or a relationship type id, a space, and a term id. [...]”  intersection := intersection of: termOrRestr termOrRestr := term-id | restriction restriction := relationship-id term-id

Proposed Solution Formalise OBO semantics via mapping to OWL 1.1 relationship: R C minCardinality=3  ObjectMinCardinality(3 R C)

Proposed Solution Formalise OBO semantics via mapping to OWL 1.1 [Term] id: A name: Example Class is_a: B relationship: R C minCardinality=3  SubClassOf(A B) SubClassOf(A ObjectMinCardinality(3 R C)) EntityAnnotation(OWLClass(A) Label(“Example Class”))

Advantages of Our Approach? Clarifies and disambiguates OBO syntax –E.g., can a relationship have more than one range? typedef-stanza := ‘[Typedef]’ … [ 'range:' termOrReserved ] …

Advantages of Our Approach? Clarifies and disambiguates OBO semantics –E.g., is cardinality qualified or not? relationship: R C minCardinality=3  ObjectMinCardinality(3 R C) –and what is the precise semantics? (ObjectMinCardinality(3 R C)) I = { x | #{ y | ( x, y ) ∈ R I and y ∈ C I } ≥ 3 }

Advantages of Our Approach? Can capture almost all of OBO in OWL 1.1, e.g.: [Typedef] id: location transitive_over: part_of  SubObjectPropertyOf( SubObjectPropertyChain(location part_of) location)) Only fails to capture –“cyclic” relations (semantics?) –negative assertions about relations (e.g., not transitive)

Advantages of Our Approach? Can easily extend OWL infrastructure to handle OBO –OWL API extended with OBO parser and serialiser –All tools built on top of API can now read/write OBO

Advantages of Our Approach? Can easily extend OWL infrastructure to handle OBO –OWL API extended with OBO parser and serialiser –All tools built on top of API can now read/write OBO

Advantages of Our Approach? Could easily extend OBO infrastructure to handle OWL –To exploit OWL reasoners –To handle (some) OWL ontologies

Advantages of Our Approach? Could easily extend OBO infrastructure to handle OWL –To exploit OWL reasoners –To handle (some) OWL ontologies

Advantages of Our Approach? OWL reasoners can deal with (most) OBO ontologies

Summary OBO $ OWL interoperability would be useful Proposed solution is –Formalise OBO syntax using BNF grammar –Formalise OBO semantics via mapping to OWL 1.1 Benefits include –Sharing of tools and ontologies OWL community gets access to OBO ontologies (and major ongoing development effort) OBO community gets access to OWL tools (and major ongoing development effort)

OBO at a Glance Ontology consists of a set of stanzas (frames) Term stanzas define terms (classes), e.g. [Term] id: GO: name: oocyte growth is_a: GO: ! cell growth relationship: part_of GO: ! oocyte morphogenesis intersection_of: GO: ! growth intersection_of: has_central_participant CL: ! oocyte –Defines GO: (oocyte growth) as a subclass of GO: (cell growth) with a part_of relationship to GO: (oocyte morphogenesis), and also as equivalent to the intersection of GO: (growth) and a relationship has_central_participant to CL: (oocyte).

OBO at a Glance Ontology consists of a set of stanzas (frames) Typedef stanzas define relationships (properties), e.g. [Typedef] id: propreo:is_described_by domain: propreo:chemical_entity range: __Description177 –Defines propreo:is_described_by and states that it has domain propreo:chemical_entity and range __Description177.

OBO at a Glance Ontology consists of a set of stanzas (frames) Instance stanzas define instances (individuals), e.g. [Instance] id: propreo:water_molecule instance_of: propreo:inorganic_solvent_molecule property_value: propreo:is_described_by propreo:CHEBI_15377 –Defines id: propreo:water_molecule as an instance of propreo:inorganic_solvent_molecule with a propreo:is_described_by relationship to the instance propreo:CHEBI_15377.