This paper describes a new syntax that can be used to write OWL 2 ontologies. The syntax, which is known as TEX-OWL, was developed to address the need for an easy-to-read and easy-to-write plain text syntax. TEX-OWL is inspired by LATEX syntax, and covers all construct of OWL 2. We designed TEXOWL to be less verbose than the other OWL syntaxes, and easy-to-use especially for quickly developing small-size ontologies with just a text editor. The important features of the syntax are discussed in this paper, and a reference implementation of a Java-based parser and writer is described.
Since OWL became a World (W3C) Wide Web Consortium recommendation, there has
been a steady stream of Web (OWL) Ontology Language ontology editing tools that
have made their way to users’ desktops. Most notably, Prote´ge´-OWL [
All of these tools offer a variety of presentation or rendering formats for class,
property and individual descriptions and axioms. These formats range from the W3C
officially required RDF/XML exchange syntax [
While the use of ontology editing tools is becoming more and more popular, there are still situations where users have to quickly write small-size ontology for testing or prototyping purposes, and directly writing the ontology with a text editor would be more effective (i.e., the overhead of learning the ontology editing tool’s functionalities and features is more than the benefit obtained by using it). These situations quite frequently occur in academic context.
W3C chose RDF/XML as the primary exchange syntax for OWL 2; indeed, this syntax must be supported by all OWL 2 tools. However, the fact that XML is extremely verbose and hard to write by hand excludes this syntax for quickly authoring and editing ontologies in a concise manner.
W3C provides alternatives to RDF/XML for OWL 2; these include Turtle, OWL/ XML, the Functional-Style Syntax and the Manchester Syntax. OWL/XML is an XML 1 http://topbraidcomposer.com/. serialization for OWL 2 that mirrors its structural specification. It is more humanreadable and easier to parse than RDF/XML; however like RDF/XML, OWL/XML is still XML. Another syntax that follows OWL 2’s structural specification is the FunctionalStyle Syntax. It is a human-readable and plain text syntax that removes the burden of XML, however like the previous two, the Functional-Style Syntax is also verbose. In fact, it has an excessive number of keywords, and typically requires the use of a large number of brackets, as its name might suggest. The Manchester Syntax is a user-friendly syntax that can be used to write OWL 2 ontologies. It is the least verbose OWL 2 syntax and when it is used to write ontology documents, it gathers together information about names in a frame-like manner as opposed to the others OWL 2 syntaxes. This nature at a first look may seem a great advantage for the Manchester Syntax, but on the other hand it makes this syntax unable of handling General (GCI) Concept Inclusions (i.e., the Manchester Syntax does not cover the expressivity of the whole OWL 2 language).
The OWL Latex-Style Syntax was created to deal with the above issues and provide users with a lightweight syntax that makes it easier to write ontologies. It has been designed primarily for writing ontology documents in simple textual editor. The syntax is discussed in detail through the rest of this paper. 2
The full specification of the TEX-OWL syntax is available at http://github.com/
matax87/TexOwl/blob/master/docs/grammar.pdf, together with several
examples of using the various syntax constructs. The primary design consideration in
developing TEX-OWL was to produce a syntax that was concise, and quick and easy to
read and write by hand. We took inspiration for developing the syntax from the LATEX
format, given it’s popularity especially in academic environments. A previous attempt
to develop a latex-like syntax was proposed in [
It was also decided that although the syntax should be aligned as much as possible with the OWL specification, for example by using keywords derived from the Functional-Style Syntax specification, the main objective would be to strive for conciseness and a reduction in the amount of time it took users to write axioms. To this end, some new keywords were created and others changed in name or name length. Moreover, it was also decided that the syntax should match as much as possible the LATEX format peculiarities of using keyword and command that start with a backslash (‘n’) symbol, with required parameters inside curly braces and optional parameters inside square brackets.
Although the TEX-OWL Syntax borrows ideas from the OWL Functional-Style Syntax, it is much less verbose. An OWL ontology written in TEX-OWL starts with an optional preface and continues with the actual ontology document. The optional preface is where prefixes can be declared via the new keyword nns. This keyword can be used also to declare a default prefix, which will be used for interpreting simple IRIs.2 The actual ontology document begins with nbeginfontologyg and ends with nendfontologyg syntax. After the begin ontology statement, users can also provide an optional ontology IRI and a even more optional version IRI typing them inside square brackets: [ontologyIRI, versionIRI]. Inside the begin/end block, ioms and put ontology annotations, as shown in the example below: user can import other ontology documents, using the keyword nimport, declare axnns <http://www.mydomain.org/african#> nbeginf o n t o l o g y g[<http://www.mydomain.org/african> ] % Animals form a c l a s s a n i m a l nc % P l a n t s form a c l a s s d i s j o i n t from a n i m a l s a n i m a l n c d i s j o i n t p l a n t % T r e e s are a t y p e o f p l a n t t r e e n c i s a p l a n t % Branches are p a r t s o f t r e e s b r a n c h n c i s a n o f o r a l l f i s p a r t o f gf t r e e g % Leaves are p a r t s o f b r a n c h e s l e a f n c i s a n o f o r a l l f i s p a r t o f gf b r a n c h g % H e r b i v o r e s are e x a c t l y t h o s e a n i m a l s t h a t e a t o n l y p l a n t s or p a r t s o f p l a n t s h e r b i v o r e nceq ( a n i m a l ncand n o f o r a l l f e a t s gf( p l a n t ncor n o f o r a l l f i s p a r t o f gf p l a n t g) g) % C a r n i v o r e s are e x a c t l y t h o s e a n i m a l s t h a t e a t a n i m a l s c a r n i v o r e nceq ( a n i m a l ncand n o e x i s t s f e a t s gf a n i m a l g) % G i r a f f e s are h e r b i v o r e s , and t h e y e a t o n l y l e a v e s g i r a f f e n c i s a ( h e r b i v o r e ncand n o f o r a l l f e a t s gf l e a f g) % L i o n s are a n i m a l s t h a t e a t o n l y h e r b i v o r e s l i o n n c i s a ( a n i m a l ncand n o f o r a l l f e a t s gf h e r b i v o r e g) % T a s t y p l a n t s are p l a n t s t h a t are e a t e n b o t h by h e r b i v o r e s and c a r n i v o r e s t a s t y p l a n t n c i s a ncandoff p l a n t , n o e x i s t s f e a t e n b y gf h e r b i v o r e g , n o e x i s t s f e a t e n b y gf c a r n i v o r e gg e a t e n b y noinv e a t s e a t s nodomain a n i m a l nendf o n t o l o g y g
A Java based reference implementation of a TEX-OWL parser and writer were created.3
They use the OWLAPI framework [
TEX-OWL is a new OWL 2 syntax that was designed in response to a demand from users for a more concise syntax that can be easily used to quickly write small-size ontologies by hand. Key features of the syntax are that it is inspired by the LATEX syntax: 2 Simple IRIs are equivalent to abbreviated IRIs where the default prefix is used and there is no need need of typing the colon (‘:’) symbol. 3 The implementation is available from http://github.com/matax87/TexOwl/. in particular the syntax uses the same format for parameters and keywords. The syntax is suited for use in simple textual editor tools. A reference implementation of a Java based parser and a writer have been produced, which may be integrated into any tool. The implementation also includes converters, which can transform TEX-OWL to other OWL 2 syntaxes and vice versa.
In order to evaluate TEX-OWL, two questionnaires were designed and sent to knowledge engineers with experience in authoring ontologies with the various OWL syntaxes. In the first questionnaire (accessible here: http://goo.gl/Cjpqtg), all OWL 2 syntaxes and TEX-OWL’s intuitiveness, conciseness, and understandability were compared using ten different examples of use. The second questionnaire (accessible here: http://goo.gl/lbFu4R) was focused on evaluating the usability of the new syntax for authoring a small ontology. Ten knowledge engineers participated to the first questionnaire, and five of them took part to the second one. Ratings were expressed according to the typical five-level Likert scale.
In summary, the results show that TEX-OWL is indeed the most concise syntax and is intuitive as the Manchester Syntax, which is the most intuitive among OWL 2 syntaxes. Moreover, users have found it easy to use TEX-OWL for authoring a small example ontology and that, in general, this syntax is better to use for writing ontologies by hands than other OWL 2 syntaxes.