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Ontohub

Ontohub is an open ontology repository which supports organisation, collection, retrieval, development, mapping, translation, and evaluation of a wide array of ontologies formalised in diverse languages.

The Ontohub team is looking forward to providing technological infrastructure for the forthcoming FOIS 2014 Ontology Competition. Accordingly, several new features are going to be launched on the Ontohub soon.

This wiki entrance aims at providing instructions and support to the Ontohub users. See also FAQ.

User Interface

Start

The home page of Ontohub provides access to all public repositories, ontologies, symbols, logics and ontology mappings stored in this hub of distributed, and yet interconnected, ontology repositories. Recently updated repositories and ontologies are listed as well.

Sign In

The full functionality of Ontohub (ontology and repository, creation, collaborative editing and development of ontologies, mapping across ontologies, visualisation, and evaluation) is available upon sign in. Every registered Ontohub user can modify and adjust its own version of interface, i.e. specific and highly personalised access to the repository content.

Repositories

Besides serving as an ontology repository, Ontohub is also a hub that links other ontology repositories. Ontohub provides a single web interface to access various ontology repositories, either hosted or mirrored on Ontohub. The button Repositories (on the menu-bar) leads to the page where all public repositories are listed and the access to their content provided. In addition, Ontohub allows creation and hosting of new repositories, the function available to all registered Ontohub users. Along the opportunity of creating a new repository, Ontohub users can get advantage of the Ontohub collaborative environment in order to develop ontologies and/or repositories in either problem or domain oriented manner. Thus, Ontohub supports reuse of ontologies stored in other ontology repositories and creation of new repositories that organize ontologies resulting from the activities of a team focused around a particular project or a specific task.

Ontohub repositories are stored as git repositories. Git provides a persistent storage and version control for ontologies, as weill as access to Ontohub repositories via the usual git tools.

It is also possible to create private repositories. These are visible only for users who have read-permission for the repository.

Ontologies

Ontology search can be performed either over whole Ontohub content ('Ontology' tab on the menu bar) or over ontologies stored within a particular Ontohub repository (Ontology browser on the page of a particular Ontohub repository).

Ontology retrieval is done by typing into the ontology browser one or many of the available search criteria:

• Ontology name
• ontology acronym
• ontology language
• a symbol or a label that an ontology contains
• a particular domain (category) that an ontology belongs to (e.g. space, biology, etc.)
• ontology type (e.g. upper, domain, task, etc.) Please note that this feature has not been implemented yet.

Since the search engine uses metadata to retrieve an ontology, all Ontohub users are encouraged to specify metadata about their ontology during the ontology upload. Having described an ontology domain, type, task, etc. increases findability of an ontology.

See FAQ on how to submit an ontology.

Categories

Ontologies can be categorised. Ontohub's category system is maintained as an OWL ontology in Ontohub itself, see [1].

Logics

Ontologies can be formulated in various logic. Ontohub supports a number of different logics, among them OWL, RDF and Common Logic.

Mappings

Under the mappings tab, you can see all mappings. Mappings always have a source and a target ontology, and provide mappings or relations between the symbols of these ontologies.

Currently, new mappings can only be created using e.g. an interpretation or an alignment in a DOL file, and uploading that DOL file.

Infrastructure

Ontohub architecture

The Ontohub infrastructure is powered by the open-source web framework Ruby on Rails for building dynamic web applications. The source code is available at github. The Ontohub git repository has separate branches development, staging and master. Software developers are introducing new features of Ontohub on its develop branch. After going through all necessary tests for stability, new features are merged to the staging (and master, i.e. visible website). In that way, the UI on the main page is always stable.

HETS

The parsing and inference backend of Ontohub is the Heterogeneous Tool Set (Hets). you can find a detailed architecture of Ontohub on page 8 of Ontohub preprint paper

Ontohub accesses the Heterogeneous Tool Set Hets via a RESTful web service interface for having the structure of ontologies analyzed. Hets already supports a large number of basic ontology languages and logics, and is capable of describing the structural outline of an ontology from the perspective of DOL, which is not committed to one particular logic.

DOL

The Distributed Ontology, Modelling and Specification Language (DOL) covers all state-of-the-art ontology languages, and provides a meta level on top of these. This meta level allows for the representation of logically heterogeneous ontologies. DOL ontologies may comprise of modules written in ontology languages with different underlying logics. Moreover, the DOL meta level constructs allow for links between ontologies such as relative interpretations or conservative extensions.

Since the Ontohub infrastructure supports DOL, it allows the Ontohub users

• to relate ontologies that are written in different formalisms;
• to re-use ontology modules even if they have been formulated in a different formalism;
• to re-use ontology tools like theorem provers and module extractors along translations between formalisms.

DOL is currently being standardised within the OntoIOp working group.

LoLa Ontology

LoLa is an ontology of (ontology) Logics and Languages. Onthub implements LoLa for structuring the repository content. The OWL core of the LoLa ontology comprises classes for ontology languages, logics, mappings (translations or projections) between ontology languages and between logics, as well as serialisations. The LoLa properties relate all of the former classes to each other. Besides its OWL module, LoLa includes additional FOL axioms for closure rules not expressible in OWL, such as non-expressible role compositions and circumscription rules for minimising the extension of default translations.

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