Cascades operators may also have parameters that describe their operation. Parameters are used for things like distinguishing the variant of an operator, or specifying the name of the file on disk to access. For example, the parameter of the the relational join operator might be the join predicate.

           Now two Model D logical operators, GET and EQJOIN are described. The Model D logical operator to retrieve the tuples of a relation from disk is the GET operator. GET has no inputs, but has two parameters -- the name of the stored relation to read off of disk, and the range variable for the table. The range variable parameter allows the resulting table to be renamed (i.e. as with the SQL "AS" keyword).

           The disk file is a parameter of GET, not an input, because the disk file is not the output of any operator. GET produces, as output, the table of tuples as read from disk.

           Model D uses the equijoin variant of the relational algebra join operator.

3. Fundamental Concepts:	<Models> <Log> <Query Trees> <Groups> <Memo> <Phys> <Item> <Rules> <Opt Stages> <Find Best> <Complexity>   3.1: EQJOIN     3.2a: Query Tree     3.2b: Equiv.     3.3a: Init Memo     3.3b: Memo     3.3c: Key     3.4: Complexity     3.5: Phys Memo     3.6: Plan     3.7: Pred.     3.8: Op Types     3.9: Rule

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