1. The organization or structure for a database. The activity of data modeling leads to a schema. (The plural form is schemata.) The term is used in discussing both relational databases and object-oriented databases. The term sometimes seems to refer to a visualization of a structure and sometimes to a formal text-oriented description. Two common types of database schemata are the star schema and the snowflake schema. 2. A formal expression of an inference rule for artificial intelligence (AI) computing. The expression is a generalized axiom in which specific values or cases are substituted for each symbol in the axiom to derive a specific inference.