Formal Definitions
Next:
Example Queries
Up:
The Domain Relational
Previous:
The Domain Relational
Formal Definitions
An expression is of the form
where the
represent domain variables, and
is a
formula
.
An atom in the domain relational calculus is of the following forms
where
is a relation on
attributes, and
, are domain variables or constants.
, where
and
are domain variables, and
is a comparison operator.
, where c is a constant.
Formulae
are built up from atoms using the following rules:
An atom is a formula.
If
is a formula, then so are
and
.
If
and
are formulae, then so are
,
and
.
If
is a formula where x is a domain variable, then so are
and
.
Page created and maintained by
Osmar R. Zaï ane
Last Update: Wed Sep 20 15:45:57 PDT 1995