Abstract
We introduce the simple query language approXQL,
which supports hierarchical, Boolean-connected query patterns.
The interpretation of approXQL queries is founded on
cost-based query transformations: The total cost of
a sequence of transformations measures the similarity
between a query and the data and is used to rank the
results.
We describe in detail the implementation of the approXQL
query processor, which uses an expanded query representation and
sophisticated indexes to compute all results
of a query in polynomial - typically sublinear - time with
respect to the database size.
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