1. A computer-implemented method for protecting data residing in a repository of an electronic product code information service against undesired data disclosure, the method comprising: defining one or more disclosure policies for an entity representing a set of items sharing a common master data attribute, each item being tagged with an electronic product code and having associated data stored in a relational database in the repository, each disclosure policy including a rule defining what attributes of the entity can be disclosed to a querying party, by creating a security view on one or more relational database objects in the database; and enforcing the one or more disclosure policies in response to receiving a query pertaining to an entity, by: transforming the received query to use the created security view for the one or more relational database objects pertaining to the entity, and returning data defined by the security view to the querying party, thereby only disclosing a subset of the data from the repository, the subset being determined in accordance with the defined one or more disclosure policies.