Restrictions

The second set of operations on the grid may be called restrictions. This is very similar to projections in the relational algebra (however the term “projection” has been reserved for different purposes).

Dimensional restriction

For a given i, take a subset A of the i-th dimension Di and define

rA = A Ä DÁ\I.

Example: a section via a member of Di.

General restriction

For a given multiindex I, take a subset A of DI and define

rA = A Ä DÁ\I.

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