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FAQ about Ontohub

The FAQ page is result of an interaction between the Ontohub users and the Ontohub team who is providing technical support to the users by giving accurate and up-to-date information about the Ontohub utilities. An active contribution and feedback of the Ontohub users is more than welcome!

What is Ontohub?

Ontohub is an open ontology repository which enables communities to share, exchange, and manage their ontologies easily.

As a member of of the OOR initiative, Ontohub supports interoperability across distributed ontology repositories.

The Ontohub engine is providing tools for

  • organising ontology collections
  • ontology retrieval
  • ontology management (reuse, editing, creation, formal mapping, evaluation)

Moreover, the Ontohub technology provides a web-based system for

  • working with multiple logical formalisms
  • management of distributed heterogeneous ontologies

What are the unique features of Ontohub?

Ontohub provides several unique features for searching, evaluating, and managing the repository content. The heterogeneous nature of Ontohub makes it possible to integrate ontologies written in various ontology languages.

How to submit an ontology?

The submission of a new ontology into Ontohub consists of the following steps:

a. Register/sign in ontohub.org

b. Select an existing repository that fits best your specific target domain, task, and ontology type; All public repositories are listed upon clicking on the 'Repository' button in the main menu; alternatively, it is possible to create a new repository (as described in the section below); certain repositories are 'read-only' while others allow editing of the repository content;

c. If uploading an ontology to the existing repository you will need to get a permission via requesting the editing rights; the permission is provided by the administrator of the repository ('owner'); After selecting (or creating) an appropriate ontology repository and acquiring the editing rights, the ontology upload can proceed through the use of file system.

d. The 'Edit' button appears on the page of each repository for which you have the editing rights. 'Edit' button leads to the interface with the editing option. So, the first step in editing is to to confirm that you want to 'Update repository'. The next step is to go to the section 'Ontology files and related files', where you can upload your ontology as a new file. The information provided there in gets stored into the file system, which can afterwords be accessed at the 'Ontology files and related files'. You might want to upload your ontology into an already existing folder that stores ontologies of your interest. In that case, in the section 'Target directory' you will need to type the exact name of the directory in which you want to store your ontology file. Into the section 'Target file name' you will need to type the ontology name together with its correct extension, e.g. name.owl, name.clif etc. A message that accompanies upload is optional but desirable as it can be helpful in tracking the history of activities and changes in repository. The next step is to 'Upload file'.

e. Since your submitted file is recognised as an ontology (via its extension), you will need to provide metadata that describe your ontology: ontology name, category (domain), ontology type, formality level, and a specific description. The inserted metadata are helpful in classification of ontologies in repository and their easier, a task specific retrieval.

When selecting metadata that describe the domain of your ontology you can select multiple fields ('Categories') that will help to characterise your ontology as specific as possible. For instance, if an ontology is about anatomy of a biological species, then the appropriate categories would be 'biology' and 'space', while a geospatial ontology can be associated with the domains 'geography' and 'space', an ontology that describes chemical structures would be associated with 'chemistry' and 'space'.

'Ontology type' and 'Formality level' provide specification of your ontology as a domain ontology, an upper level ontology etc. Please note that the classification of ontology types and formality levels mostly follows the OMV specifications. Modifications and revisions to this classification are work in progress.

'Description' of ontology provides an important narrative, i.e. information that will additionally help users (people and machines) to capture the targets and aims of the ontology designer.

How to edit an ontology?

How to evaluate an ontology?

Which logical formalisms (languages) are supported by Ontohub?

see the list of logics.

Why does Ontohub support multiple (onto)logical formalisms?

Ontohub supports multiple (onto)logical formalisms in order to admit inclusion and interoperability of ontologies distributed across various repositores. A variety of languages is used for formalising ontologies. Some of these, such as RDF (mostly used for data), OBO and certain UML class diagrams, can be seen more or less as fragments and notational variants of OWL, while others, like F-logic and Common Logic (CL), clearly go beyond the expressiveness of OWL. [1]

In other words, Ontohub respects the existing plurality of formalisms, expressivities and aims, as they are found across diverse scientific communities. While accepting the plurality of formal languages and tools (e.g. CL, OWL, RDF, etc), methodologies and perspectives, Ontohub provides interoperability of domain needs and exchange of knowledge on a formal level. Thus, Ontohub supports linking ontologies across ontology languages, and creating distributed ontologies as sets of basic ontologies and links among them. The links (mappings) in Ontohub have formal semantics, and therefore enable new reasoning and interoperability scenarios between ontologies. [1]

What is a single ontology?

A single ontology, also labeled as 'basic' ontology (DOL terminology), is any ontology that is written in a single ontology language and it does not include any other ontology (or ontology module) within its content.

What is a distributed ontology?

A distributed ontology is an ontology which is composed of two or more ontologies (modules). A distributed ontology can be written in a single (homogeneous) or diverse (heterogeneous) ontology languages. The content of a distributed ontology may be distributed across diverse ontology sources and repositories. Ontohub allows storage and management of heterogeneous and distributed ontology content.

What is a heterogeneous ontology?

A heterogeneous ontology is an ontology which is composed of more than one ontology (module) and its content and structure are formalised in more than one ontology language.


  1. 1.0 1.1 Mossakowski, Till, Christoph Lange, and Oliver Kutz. "Three Semantics for the Core of the Distributed Ontology Language." FOIS. 2012. PDF