Appendix B
Glossary ActiveX control: A reusable software component that can be added to an application, reducing development time in the process. ActiveX is a Microsoft technology; ActiveX components can be used only by developers who work on Windows development systems. aggregate function: A function that produces a single result based on the contents of an entire set of table rows. Also called a set function. alias: A short substitute or nickname for a table name. applet: A small application, written in the Java language, stored on a Web server that is downloaded to and executed on a Web client that connects to the server. application program interface (API): A standard means of communicating between an application and a database or other system resource. assertion: A constraint that is specified by a CREATE ASSERTION statement (rather than by a clause of a CREATE TABLE statement). Assertions commonly apply to more than one table. atomic: Incapable of being subdivided. attribute: A component of a structured type or relation. back end: That part of a DBMS that interacts directly with the database. catalog: A named collection of schemas. client: An individual user workstation that represents the front end of a DBMS — the part that displays information on a screen and responds to user input. client/server system: A multiuser system in which a central processor (the server) is connected to multiple intelligent user workstations (the clients). cluster: A named collection of catalogs.