18. A system for indexing and searching entity-relationship data, comprising: a processor configured to: receive indication of a database of entity-relationship data which includes identifiers of entities and indications of relationships between the entities, indicating which entities are related to each other; represent the entities of the indicated database as respective documents, each document containing content and metadata of a respective entity; represent the entities of the provided database as respective categories; represent each relationship instance, which indicates a relationship between a plurality of entities, in the database, as a category set that contains categories of all participating entities in the relationship; and index the entity-relationship data of a populated logical document model as an inverted index.
18. A system for indexing and searching entity-relationship data, comprising: a processor configured to: receive indication of a database of entity-relationship data which includes identifiers of entities and indications of relationships between the entities, indicating which entities are related to each other; represent the entities of the indicated database as respective documents, each document containing content and metadata of a respective entity; represent the entities of the provided database as respective categories; represent each relationship instance, which indicates a relationship between a plurality of entities, in the database, as a category set that contains categories of all participating entities in the relationship; and index the entity-relationship data of a populated logical document model as an inverted index. 20. The system of claim 18 , including: a free-text query component for processing a free-text query by searching over a free-text content field encapsulating the searchable content of the entities.