Ontology repositories
Ontology repositories are usually more specific that semantic web search engines and their navigation/search interfaces can vary greatly. They offer tools that may be specific to the type of applications the repository was designed for.
BioPortal
Description: BioPortal is a repository of over 300 biomedical ontologies and includes tools for working with these ontologies.
Available at: http://bioportal.bioontology.org/
Unique strength: Holds most widely used Biomedical ontologies. Allows ontologies to be browsed, searched, and reviewed. Allows uses to create notes on ontologies terms. Allows arbitrary text to be annotated with ontology terms. Also supports search of biomedical resources (e.g. PubMed) for combinations of terms from ontologies. Allows programmatic access to ontologies through a REST interface.
Possible drawback: Holds only biomedical ontologies. Portal is available as a VM which can be hosted independently and hold ontologies from other domains.
Cupboard
Description: Cupboard is an ontology repository with some advanced features, powered by Watson Semantic search engine.
Available at: http://cupboard.open.ac.uk:8081/cupboard-search/
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DERI Vocabularies
Description: is a repository and can be used as an online ontology editor.
Available at: http://vocab.deri.ie/
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Knoodl
Description: Knoodl is a repository and collaborative ontology management tool.
Available at: http://knoodl.com/
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Ontology Design Patterns
Description: a repository for design patterns and ontology modules following the patterns.
Available at: http://ontologydesignpatterns.org/
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Prefix.cc
Description: is a namespace lookup service, which can be seen as a kind of vocabulary directory.
Available at: http://prefix.cc/
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Schemapedia
Description: is another ontology directory.
Available at: http://schemapedia.com/
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SchemaWeb
Description: it is a quite old ontology directory, but it is still used, apparently.
Available at: http://www.schemaweb.info/
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