  The web is changing the way in which data warehouses are designed, used, and
queried. With the advent of initiatives such as Open Data and Open Government,
organizations want to share their multidimensional data cubes and make them
available to be queried online. The RDF data cube vocabulary (QB), the W3C
standard to publish statistical data in RDF, presents several limitations to
fully support the multidimensional model. The QB4OLAP vocabulary extends QB to
overcome these limitations, allowing to im- plement the typical OLAP
operations, such as rollup, slice, dice, and drill-across using standard SPARQL
queries. In this paper we introduce a formal data model where the main object
is the data cube, and define OLAP operations using this model, independent of
the underlying representation of the cube. We show then that a cube expressed
using our model can be represented using the QB4OLAP vocabulary, and finally we
provide a SPARQL implementation of OLAP operations over data cubes in QB4OLAP.
