Modeling the Data Sources

Data source descriptions which specify the relationship between the relations in the mediated schema and those in the local schemas at the sources should be provided. The description of a source specifies its

• contents
• attributes
• constraints on its contents
• completeness and reliability
• query processing capabilities

Besides, using the descriptions of the sources, we should be able to detect the following:

• overlapping and contradictory data among sources
• semantic mismatches among sources
• differing naming conventions for data values among sources