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[protege-owl] Database and Owl Ontology

Sarah G nvme_06 at
Sun Aug 16 18:31:34 PDT 2009

 Thanks, Tim.  Is there an example on protege's website on what an ontology looks like when it is connected to a database? 

Also, when you import the database to the ontology should you select each table to the appropriate class? Example:

I would select the table called Vehicle that I imported from my database into the ontology and select the class called vehicle in the ontology to be mapped to each other is that correct? Thanks.


From: tredmond at
To: protege-owl at
Date: Sat, 15 Aug 2009 23:59:45 -0700
Subject: Re: [protege-owl] Database and Owl Ontology

There are several reasons why people would want to put a very large ontology into a database.  For example,

1. a database can be loaded on a machine with limited memory.  This allows people to work with ontologies on machines with limited capabilities when access to more capable machines is  not possible.

2. an ontology in a database can be loaded very quickly allowing people to access an ontology without having to (re)parse the entire ontology

3. a server may need to open many ontologies open at the same time and to be able to open large ontologies quickly based on demand from users or clients.  This is important for an ontology repository for example.

The main reason for  not wanting to use a database backend is its complexity and its much slower performance.

But it is also important to point out that the Manchester OWL api (used by Protege 4) can hold very large ontologies in limited memory.  So for example, my 2GB old laptop is almost capable of loading snomed.  This may suggest that the most important reason for having a database backend for the Manchester OWL API is the third case.  


On Aug 15, 2009, at 7:48 PM, Sarah G wrote:

Hi All,
Could someone please explain why you should have/use a relational database as backend for an ontology? I am new to using owl and was wondering why or if I will need to have a database.

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