1. XML-QL: A Query Language for XML Submission to WWW Consortium August 19, 1998
Alin Deutsch, University of Pennsylvania
Mary Mernandez, AT&T Labs
Daniela Florescu, INRIA
Alon Levy, University of Washington
Dan Suciu, AT&T Labs
Reviewed by Terry E Weymouth
Monday, February 14, 2000

2. Example Data <bib>
<book year="1995"> <!-- A good introductory text -->
<title> An Introduction to Database Systems </title>
<author> <lastname> Date </lastname> </author>
<publisher> <name> Addison-Wesley </name > </publisher>
</book>
<book year="1998">
<title> Foundation for Object/Relational Databases:
The Third Manifesto </title>
<author> <lastname> Darwen </lastname> </author>
</bib>

3. Example Query
WHERE <book> <title> $t </> <publisher><name>Addison-Wesley </> </> </> CONTENT_AS $p IN "
CONSTRUCT<result><title> $t </> WHERE <author> $a</> IN $p CONSTRUCT <author> $a</>
</>

4. Results <result>
<title> An Introduction to Database Systems </title>
<author> <lastname> Date </lastname> </author>
</result>
<title> Foundation for Object/Relational Databases: The Third Manifesto </title>
<author> <lastname> Darwen </lastname> </author>

5. Some Problems Addressed
How to extract data (information?) from large XML documents or document stores.
How to exchange XML data between disparate locals (exchanging queries might be more efficient)
How to exchange XML data between different user communities
How to integrate data from multiple XML sources

6. Components and features
Matching with Structural Patterns
Binding variables to elements in the match
construction
joining elements by value
Grouping with nested and combined queries
Binding variables to tags in the match (also Skolem functions)
Regular expressions for path matching
Construction
query results in XML
transforming XML data
Embedding queries in data

7. Suggested Extensions
User defined predicates
Regular string expressions - element content (what about attributes)
Name Spaces
Aggregates (e.g. GROUP-BY) - with summation-type functions
Semi-joins (i.e. joins over optional elements)

8. Extra-structure elements
Comments
Data Model Features
ordered or unordered sub-elements (imposing order in results of query for unordered model!)
graph structure: semi-structured data
ID’s and ID references
Extra-structure elements
e.g. comment tags, document specifications such as occurrence and ordering information (DTD)