1. A computer program product, the computer program product comprising: a non-transitory computer readable storage medium having computer readable program code embodied therein, wherein the computer readable program code, when executed by at least one processor of a computer, is configured to perform: retrieving a report specification that includes one or more query declarations of data to be presented and one or more layout declarations describing how the data is to be rendered; retrieving a semantic model with concepts, wherein the semantic model comprises a Web Ontology Language (OWL) model; generating a Business Intelligence (BI) metadata model by executing transformations that transform concepts in the semantic model to BI metadata constructs by: constructing a table for each semantic class in the semantic model; constructing a column for each semantic data type property restriction; and constructing a relationship for each semantic object property restriction; receiving a request for a combined report that combines result sets from the semantic model and one or more relational data sources comprising relational databases; constructing one or more first queries using the BI metadata model and the one or more query declarations; executing the one or more first queries on the semantic model to obtain one or more semantic result sets; executing one or more second queries against one or more relational data sources to obtain one or more relational data source result sets; combining the one or more semantic result sets and the one or more relational data source result sets to construct one or more combined result sets; and rendering the one or more combined result sets to form a combined report based on the one or more layout declarations.