FAQ

Table of Contents The Protege Plugins complains: No suitable driver found for .. (driver) Protégé: No "JDBC drivers" tab in the preferences Protege does not show the Ontop tabs! Casing problems with SQL identifiers MySQL Server does not support double quotes as identifiers What is the mapping syntax? How can I start using -ontop-? How Do I use ontop together with Protege? Why Sesame Workbench refuse to delete some repositories? What does -ontop- support regarding SQL and SPARQL? What is the difference between Quest and -ontop-? How fast is -ontop- compared to the rest? Is it also open source? How can I report a bug or ask other questions?

The Protege Plugins complains: No suitable driver found for .. (driver)

You need to download and install the right driver in Protege. See Setting up JDBC Drivers and JDBC Information

Protégé: No "JDBC drivers" tab in the preferences

You probably can see the following message in the Protégé console: org.osgi.framework.BundleException: Activator start error in bundle org.protege.osgi.jdbc.prefs [20].) org.protege.osgi.jdbc.RegistryException: java.lang.ClassNotFoundException: org.h2.Driver

Please go to the Preferences and click on "Reset preferences".

Protege does not show the Ontop tabs!

To see the tabs go to Windows-> tabs-> Ontop Mappings and Ontop SPARQL.

Casing problems with SQL identifiers

If you experience the following error message: "Error in identifying column name", it may be due to casing problems with the SQL identifiers used in your mappings. See this dedicated page.

MySQL Server does not support double quotes as identifiers

To use ontop and Mysql Server ANSI_QUOTES mode should be enabled. By default the " character can be used to enclose string literals just like ', while in ANSI_QUOTES mode the " character can be used to enclose identifiers just like ` .

What is the mapping syntax?

To learn the mapping language [page](https://github.com/ontop/ontop/wiki/ObdalibQuestMappinglanguage). To see how to produce efficient mappings (under construction.)

How can I start using -ontop-?

We recommend to Start following an easy example: this example

How Do I use ontop together with Protege?

See this page.

Why Sesame Workbench refuse to delete some repositories?

For deleting metadata about a repository, the Sesame Workbench should be able to create an instance of this repository. However, if the repository configuration is invalid (due to, for instance to bad mapping and ontology files), such an instance cannot be created. To avoid this situation, the configuration is validated in depth when a new repository is added to the Workbench. However, if the mapping and ontology files are changed afterwards, we offer no protection. Fortunately, there is some easy workarounds.

What does -ontop- support regarding SQL and SPARQL?

See the known issues and limitations here

What is the difference between Quest and -ontop-?

Quest is the reasoner behind -ontop-. -ontop- is the whole framework. For more information check more info about Quest

How fast is -ontop- compared to the rest?

Very fast! See our Benchmarks.

Is it also open source?

Yes! The -ontop- framework is available under the Apache License, Version 2.0

How can I report a bug or ask other questions?

Send us an email to our mailing list: https://groups.google.com/d/forum/ontop4obda .