Abstract: A user-friendly query modeling tool and method, for representing, creating, modifying and modeling a query language statement for use in retrieving data from a database. In accordance with the present invention, the tool includes a user interface for receiving or building and manipulating a query, a query model definition for use in populating instances of one or more query models, and a model content provider for receiving query elements from the user interface and providing them to the query model, and conversely, for retrieving query elements from the query model and providing them to the user interface. The user interface enables the user to easily group and ungroup query elements by providing a visual tool for selecting query elements to be grouped and ungrouped.

Abstract: A two-valued logic relational database system handles missing information in a consistent way, such that query performance optimization and other techniques that break down in a three-valued logic relational database systems, can be applied. This database system introduces a NOT FOUND value to designate empty or missing information. The NOT FOUND value is introduced in all possible domains from which a constant, variable or tuple attribute may draw its value, including cases where that value is a collection of values such as a set or multiset.

Abstract: A user-friendly query modeling tool and method, for representing, creating, modifying and modeling a query language statement for use in retrieving data from a database. In accordance with the present invention, the tool includes a user interface for receiving or building and manipulating a query, a query model definition for use in populating instances of one or more query models, and a model content provider for receiving query elements from the user interface and providing them to the query model, and conversely, for retrieving query elements from the query model and providing them to the user interface. The user interface enables the user to easily group and ungroup query elements by providing a visual tool for selecting query elements to be grouped and ungrouped.

Abstract: A user-friendly query modeling tool and method, for representing, creating, modifying and modeling a query language statement for use in retrieving data from a database. In accordance with the present invention, the tool includes a user interface for receiving or building and manipulating a query, a query model definition for use in populating instances of one or more query models, and a model content provider for receiving query elements from the user interface and providing them to the query model, and conversely, for retrieving query elements from the query model and providing them to the user interface. The user interface dynamically adapts to selections by a user in creating or editing a query statement, thus providing a helpful and user-friendly visual interface.