Local As View (LAV) Approach

For each data source S, a rule over the relations in the mediated schema is written that describes which tuples are found in S. This is an application of a much broader problem called "Answering Queries using Views". (** It also applies to view design and selection in Data Warehousing.)

Query reformulation in LAV is more complex. However, it has important advantages compared to GAV: adding new sources and specifying constraints in LAV are easier.

- equivalent rewritings vs maximally-contained rewritings

• The Bucket Algorithm
• The Inverse-Rules Algorithm
• The Minicon Algorithm
• The Shared-Variable-Bucket Algorithm
• The CoreCover Algorithm
• Comparison of the Algorithms