Abstract
XML documents may have partially specified or missing schema information,
motivating the use of a structural summary, which can be computed from
the data.
These summaries are valuable for evaluating queries. DataGuides and
1-index are two representatives of the summaries. They encoding all
pathes information, so that for simple path expression, they can provide
exact answer quickly.
However the size of DataGuides and 1-index maybe very large. Is it
possible to sacrifice accuracy to reduce the space requirement? In
ICDE2002, A(k)-index is proposed , which is a family of approximate
structural summaries. As k=1,2,..., the size of it grows larger and it
can ensure the answer of simple path of length k(or less) in A(k)-index
is an exact answer. This method give us a choice to trade off between
space and accuracy.
In this talk DataGuide and 1-index will be briefly introduced as the
backgroud.
