dc.contributor.author | Raschid, Louiqa | en_US |
dc.contributor.author | Vidal, Maria Esther | en_US |
dc.contributor.author | Gruser, Jean-Robert | en_US |
dc.date.accessioned | 2004-05-31T22:43:42Z | |
dc.date.available | 2004-05-31T22:43:42Z | |
dc.date.created | 1997-03 | en_US |
dc.date.issued | 1998-10-15 | en_US |
dc.identifier.uri | http://hdl.handle.net/1903/872 | |
dc.description.abstract | We support flexible query processing with autonomous networked
information sources. Flexibility allows a query to be accepted
in a dynamic environment with unavailable sources. Flexibility
provides the ability to identify equivalent sources, based on
their contents; these equivalences are used to eliminate
redundancy and provide alternate query plans, when some source is
unavailable. We determine the best plan, i.e., the least-cost
non-redundant plan, based on a cost-model for autonomous sources.
These features are supported by a meta-wrapper component within
the mediator. The meta-wrapper interface
is defined by a structure and supported operations.
WHOQL is a query language for queries and plans;
it can represent sequential execution to obtain safe plans,
and plans with redundancy (alternatives). A language WHODL defines
the mapping from the meta-wrapper interface to
each source. WHODL also describes the contents of a
source. This content definition is used to determine equivalences
of autonomous sources. We obtain a least-cost non-redundant
plan in a dynamic environment. A meta-wrapper cost model uses
three underlying sources of information: a
selectivity model;
a cost model for operators in the meta-wrapper; and a cost
estimator for the query response time. The estimator uses a
parameterized feedback technique to learn from query feedback,
and to determine the relevance of various factors that affect
response time. The cost model also provides
feedback to the plan generator on low-cost plans.
(Also cross-referenced as UMIACS-TR-97-07) | en_US |
dc.format.extent | 279618 bytes | |
dc.format.mimetype | application/postscript | |
dc.language.iso | en_US | |
dc.relation.ispartofseries | UM Computer Science Department; CS-TR-3745 | en_US |
dc.relation.ispartofseries | UMIACS; UMIACS-TR-97-07 | en_US |
dc.title | A Flexible Meta-Wrapper Interface for Autonomous Distributed
Information Sources. | en_US |
dc.type | Technical Report | en_US |
dc.relation.isAvailableAt | Digital Repository at the University of Maryland | en_US |
dc.relation.isAvailableAt | University of Maryland (College Park, Md.) | en_US |
dc.relation.isAvailableAt | Tech Reports in Computer Science and Engineering | en_US |
dc.relation.isAvailableAt | UMIACS Technical Reports | en_US |