Schema Evolution publication categorizer

This technical report describes how IQL queries are processed in the AutoMed heterogeneous data integration system, and also how data migration can be supported.
We start with an outline of the IQL language in Section 2. We then consider in Section 3 an abstract representation of this textual IQL and describe the ASG class that implements this abstract representation.
Given a query expressed using the constructs of one schema, it may be necessary to reformulate this query so that it is expressed over the constructs of other target schemas that are linked to it by AutoMed transformation pathways. For
example, a query expressed on a global virtual schema needs to be reformulated into a query over the local data sources in order to be evaluated. Software that does this is described in Section 4.
Next, we consider how IQL queries are evaluated. The implementation of software to evaluate IQL queries that contain various built-in functions is described in Section 5. Retrieving data from data sources is described in Section 6. In Section 7 some example code is given that shows how an IQL query would be
processed from top to bottom. Some examples of IQL queries are also given. Finally, Section 8 discusses how data migration from one or more data sources to a target data source can be supported.