Version 1.1, 12th January 2004

Introduction

CQL stands for Common Query Language. It is a formal language for representing queries to Information Retrieval systems such as web indexes, bibliographic catalogs and museum collection information.

Traditionally, query languages have fallen into two camps:

• Powerful and expressive languages which are not easily readable or writable by non experts. Examples could include SQL, PQF, and XML Query.
• Simple and intuitive languages which are not powerful enough to express complex concepts. For example, CCL or google's query language.

CQL's goal is to combine simplicity and intuitiveness of expression with the richness of Z39.50's type-1 query. Just as any good text based interface, CQL is intended to 'do what you mean' for simple, every day queries, while allowing means to express complex concepts when necessary.

Table of Contents

• Definition
  • General CQL rules
  • BNF syntax
  • XCQL (CQL in XML)
• Context Sets
  • CQL context set
  • Dublin Core context set
• Sample CQL queries
• Other Resources
  • Gentle Introduction to CQL
• Implementations
• Presentations