Abstract: A data processing apparatus and method for creating data analysis applications using reusable software operators . An initial operator is provided for converting source information into a virtual database format. Query operators are provided for receiving data in a virtual database format, processing the data in the virtual database, and outputting the results of the processing in another virtual database which has the same schema as the received virtual database. A plurality of query operators may be combined in order to customize the processing of the virtual database data. A terminal operator is provided for converting data in a virtual database into an external format which may then be further processed by an external operator. By combining initial, query, terminal, and external operators, users may create customizable data processing applications. In accordance with one embodiment of the invention, operators are provided for analyzing the difference between a first document and a second document.

Abstract: Techniques for analyzing and controlling operation of a system of cooperating processes. A library of system calls used by the processes is replaced by a dynamically-linked library which performs the system calls and also sends messages indicating that the system calls have been performed. The messages are received by a display system which responds to the messages by making a graphical display showing the current state of the system of processes. The graphical display displays the system of processes as a tree. Nodes in the tree represent the processes in the system and resources such as files used by the processes; edges in the tree represent relationships between processes and other processes or resources. Users may control which system calls result in messages, may control the rate at which the display system responds to the messages, and may also control execution of the processes.