Part VII: Query

Predica queries navigate, filter, reshape, and aggregate values through paths in the model. This part introduces that surface notation from the user's point of view: how to ask for suppliers in London, how to move through relationships, how to expose a view, and how to collect or summarise the values reached by a path.

The technical account is given later in the Semantics part. In short, query expressions denote logic frames. When a query result is displayed as a table or relation, that display is an observed extension of the frame, not a separate relation-valued meaning for the query expression.