A Meta-Wrapper for Scaling up to Multiple Autonomous Distributed Information Sources

Current mediator and wrapper architectures do not have the flexibility to scale to multiple wrapped sources, where some sources may be redundant, and some sources may provide incomplete answers to a query. We propose a metawrapper component which is capable of handling multiple wrapped sources, in a particular domain, where the multiple sources provide related information. The metawrapper makes these sources transparent to the mediator, and provides a single meta-wrapper interface for all these sources. Source descriptions specify the content and query capability of the sources. These are used to determine the meta-wrapper interface and to decide which queries from a mediator can be accepted. Sources are partitioned into equivalence classes, based on their descriptions. These equivalence classes are partially ordered, and the lattices that correspond to these orderings are used to identify the relevant sources for a query submitted by the mediator. If there is redundancy of the sources, the meta-wrapper identifies alternate sources for the query. A meta-wrapper cost model is then used to select among alternate relevant sources and choose the best plan.