Abstract: A method of operating a database system access to plurality of heterogeneous databases, each of said databases having a structure based on a respective database model and storing a plurality of data entities having attributes and occurrences within the structure; providing an interface database, the interface database populated with a plurality of unique, multi-character expressions associated with the data entities of plurality of databases, whereby the plurality of unique, multi-character expressions are defined by assigning to every entity, every attribute and every entity occurrence a unique, multi-character expression, the expression having a predetermined hierarchical structure which defines the relationship between each entity, attribute and entity occurrence with every other entity, attribute and entity occurrence in the interface database and storing said expressions in an expression set table linking each element of each expression to a hierarchical level and a position in a data model.

Abstract: A database system configures a storage model in accordance with a hierarchical tree-like structure to enable fast and comprehensive data extraction functions. A plurality of entities, attributes and entity occurrences are each assigned a unique, multi-character expression. The expression has a predetermined hierarchical structure which defines the relationship between each entity, attribute and entity occurrence with every other entity, attribute and entity occurrence. The expressions are stored in an expression set table linking each element of each expression with a natural language phrase or data definition. Events are recorded in an entity history table each event having an associated expression. Data is extracted from the database according to a multi-character query expression comprising characters that are deterministic to the query and characters that are non-deterministic to the query.