Fuzzy Querying Capability at Core of a RDBMS - Advanced Database Query Systems - page 184

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KEY TERMS AND DEFINITIONS
Derivation Principle: Given a (fuzzy) SQLf query, we can derive a (boolean) SQL query that
retrieves same rows (strong derivation) or a set of row with some (few) extra rows (weak derivation).
Fuzzy Access Methods: Stored tables are scanned with different methods according physical orga-
nization and querying conditions, such methods are extended to compute satisfaction degree in case of
fuzzy queries, these are the Fuzzy Access Methods.
Fuzzy Parse Tree: Memory structure that the query engine parse module will generate for represent-
ing and manipulating a fuzzy query.
Fuzzy Physical Relational Operators: Relational Algebra operators join, selection and projection
have their different implementations, they are extended to compute satisfaction degree in case of fuzzy
queries, these are the Fuzzy Physical Relational Operators.
Fuzzy Plan Tree: Planner/optimizer generated memory structure that holds a fuzzy relational alge-
bra tree where each node is annotated with the Fuzzy Physical Relational Operators or Fuzzy Access
Methods that executor module will use in order to compute the query answer.
Fuzzy Query Tree: Query engine internal memory structure that holds a fuzzy relational algebra
tree corresponding to the fuzzy query that is been processed.
Fuzzy Set: Special kind of set where elements are characterized by a membership function in the real
interval [0,1] where 1 indicates element completely included, o indicates element completely excluded,
otherwise, element is gradually included.
Loose Coupling: Software architecture strategy for adding extra functionality to an existing system
by means of a logic layer implemented in an external program.
SQLf: Extension of the relational database standard query language SQL allowing querying condi-
tions in fuzzy logic based on linguistic terms that user defines according own preferences.
Tightly Coupling: Software architecture strategy for adding extra functionality to an existing system
by means of source code extension preserving original system architecture.