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It is well known that end-users have problems to write even simple SQL queries. The new SPARQL query language for RDF databases is a step in the right direction, but is still not suitable for end-users. This lead us to creating a more convenient approach in which end-users could retrieve structured data from the database through a graphical query language named GQL. GQL graphical query language is based on OWL ontology language and SPARQL query language for RDF data. GQL visualization format is based on UML graphical language. To achieve interoperability between all these techniques, a true subset approach did not work–minor modifications were required to achieve a functional solution. The proposed approach is applicable also to querying data from the legacy relational databases through database export to OWL/RDF format.