OWL verbalizer demo

Introduction

This demo shows how an ontology that is written in OWL 2 XML is verbalized in Attempto Controlled English (ACE). This conversion is designed to be reversible, i.e. one can convert the ACE representation back into OWL so that no loss in meaning occurs.

The source code, issue list, documentation etc. of the OWL verbalizer are available at https://github.com/Kaljurand/owl-verbalizer.

Demo

How is the verbalization done?

We first rewrite the class expressions and axioms via a limited number of more basic class expressions and axioms. The motivation behind this step is to replace axioms like

ObjectPropertyDomain(R C)

which have very little syntactic structure and contain logic-specific words like `domain'.

The remaining class expressions are mapped to ACE noun phrases and the remaining axioms to ACE sentences. OWL properties are ACE verbs or of-constructs and OWL individuals are ACE proper names. The following table shows an example how the OWL constructs are mapped to ACE constructs.

ACE allows relative clause coordination and embedding of relative clauses into other relative clauses. This gives us quite a bit of flexibility in expressing more complex OWL class expressions. For example,

ObjectSomeValuesFrom(eat ObjectComplementOf(ice-cream))

would be verbalized as an ACE noun phrase

something that eats something that is not an ice-cream

Still, verbalizing very complex class expressions would require a support for parentheses which ACE does not offer. We do not see it as a shortcoming, rather it is a natural restriction on the complexity of class expressions (which should be readable for others to understand).

Finally, we apply some simple modifications to make the sentences more readable, e.g. we try to remove negations and reorder the elements in coordination.

OWL entities vs ACE content words

The quality of the verbalization depends somewhat on the morphologic and orthographic nature of the names used for individuals, classes and properties in the input ontology. The verbalizer assumes that all individuals are denoted by singular proper names (preferably capitalized), classes by singular common nouns, and properties by transitive verbs in their infinitive form or as singular nouns. These restrictions are needed because the names will be used in certain syntactic constructions or will undergo certain morphological changes.

• Individuals (proper names) are used in the subject and object positions without a determiner, e.g. "Every man knows John.", "John is a man."
• Classes (common nouns) are used in the subject and object positions with determiners like every, no, a, at least 2; e.g. "Every man knows something.", "No woman likes a spider.", "Every baltic-state borders at least 2 countries.".
• Properties (transitive verbs) are often used in singular, e.g. "Every boy owns a bike.", but under negation (i.e. ObjectComplementOf) will stay in infinitive, e.g. "Every one-year-old is a child that does not own a bike.". In some cases, most often when verbalizing the ObjectPropertyRange-construct, a past participle form is used in order to construct a passive sentence, e.g. "Everything that is owned by something is a possession."

The default synthesis of entity IRI surface forms just preserves the IRI fragment (the part after '#' or the last '/') but one can add annotations to the input ontology to specify the desired surface form, e.g.

<AnnotationAssertion> 
	<AnnotationProperty IRI="http://attempto.ifi.uzh.ch/ace_lexicon#CN_pl"/>
	<IRI>#man</IRI>
	<Literal>men</Literal>
</AnnotationAssertion>

The following annotation properties are supported:

In the csv-mode, the IRI is returned as it is together with the morphological type that applies in the given context, e.g:

pn_sg	http://www.example.org/story.owl#John
f	is
f	a
cn_sg	http://www.example.org/story.owl#man
f	.

In the ace-mode, in case an object property has the CN_sg annotation then the property is verbalized as a relational noun, using an of-construct, Saxon genitive, or the whose relative pronoun. Examples:

John is a father of Mary.
Mary's father is John.
Everything whose father is John ...

This is an experimental feature which does not always work correctly.