The Tukwila Data Integration System
The Tukwila data integration system introduces a number of new
techniques for query reformulation, optimization, and execution.

Modules
- Client/user interface
- This module allows the user to select a mediated schema and to enter a
query.
- The query is fed to the reformulator, which translates it into a
logical plan and sends it to the later stages.
- Once query execution is complete, the execution engine notifies the
user interface, and sends back the query results.
- Reformulator
- The reformulator takes a query over the mediated schema and translates
it over available web sources, generating a logical plan for the
optimizer.
- It makes use of the data source catalog and various metadata
information.
- The for Tukwila is being developed by
Rachel Pottinger.
- Data source catalog
- The source catalog contains mappings from the available data sources
to the mediated schema.
- It also contains information about data coverage, estimated access
costs, etc.
- Optimizer which supports partial and incremental optimization
- The Tukwila optimizer has the ability to specify partial plans in the
presence of uncertainty.
- It can incrementally re-optimize a query based on new information.
- The optimizer also generates condition-action rules for the execution
system, telling it how to handle various exceptions.
- The Tukwila optimizer is under development by
Marc Friedman.
- Adaptive query execution engine
- Tukwila's execution engine supports a number of new features:
- Rules for handling exception conditions.
- Incremental execution, with statistics gathering and reporting.
- Enhanced join operators to support a more data-driven model.
- A collector operator which supports dynamic processing of
information from overlapping data sources.
- The execution system is under development by
Zack Ives.
- Data source wrappers
- Currently wrappers are available for ODBC-compliant data sources.
- New wrappers are under development by Hakim Weatherspoon.
Papers
- Zachary Ives, Daniela Florescu, Marc Friedman, Alon Levy, Daniel S.
Weld. An Adaptive Query Execution System for Data Integration. To
appear in SIGMOD 99.