$Id: README,v 1.11 2002-11-03 17:37:14 mike Exp $

cql-java - a free CQL compiler, and other CQL tools, for Java


INTRODUCTION
------------

cql-java is a Free Software project that provides:

* A set of classes for representing a CQL parse tree (a base CQLNode
  class, CQLBooleanNode and its subclasses, CQLTermNode, etc.)
* A CQLCompiler class (and its lexer) which builds a parse tree given
  a CQL query as input.
* A selection of compiler back-ends to render out the parse tree as:
	* XCQL (the standard XML representation)
	* CQL (i.e. decompiling the parse-tree)
	* PQF (Yaz-style Prefix Query Format) [### NOT YET]
* A random query generator, useful for testing.

CQL is "Common Query Language", a new query language designed under
the umbrella of the ZING initiative (Z39.59-International Next
Generation).  More information at
	http://zing.z3950.org/cql/index.html

XCQL is "XML CQL", a representation of CQL-equivalent queries in XML
which is supposed to be easier to parse.  More information at
	http://www.loc.gov/z3950/agency/zing/srwu/xcql.html
(not much more, though)

But if you didn't know that, why are you even reading this?  :-)


What's what in this distribution?

	README	This file
	VERSION	The version-number of this distribution
	src	Source-code for the cql-java library
	lib	The compiled library file, "cql-java.jar"
	bin	Simple shell-scripts to invoke the test-harnesses
	docs	Documentation automatically generated by "javadoc"
	test	Various testing and sanity-checking frameworks
	etc	Other files: CQL Grammar, generator properties, etc.

"Installation" of this package would consist of putting the bin
directory on your PATH and the lib directory on your CLASSPATH.


SYNOPSIS
--------

Using the test-harnesses:

	$ CQLParser 'title=foo and author=(bar or baz)'
	$ CQLLexer 'title=foo and author=(bar or baz)'
		(not very interesting unless you're debugging)
	$ CQLGenerator etc/generate.properties seed 18

Using the library in your own applications:

	import org.z3950.zing.cql.*

	// Building a parse-tree by hand
	CQLNode n1 = new CQLTermNode("dc.author", new CQLRelation("="),
				     "kernighan");
	CQLNode n2 = new CQLTermNode("dc.title", new CQLRelation("all"),
				     "elements style");
	CQLNode root = new CQLAndNode(n1, n2);
	System.out.println(root.toXCQL(0));

	// Parsing a CQL query
	CQLParser parser = new CQLParser();
	CQLNode root = parser.parse("title=dinosaur");
	System.out.print(root.toXCQL(0));
	System.out.println(root.toCQL());
	System.out.println(root.toPQF(qualSet));
	// ... where `qualSet' specifies CQL-qualfier => Z-attr mapping


DESCRIPTION
-----------

See the automatically generated class documentation in the "doc"
subdirectory.  (It's not all there yet, but it's coming.)


AUTHOR
------

All code and documentation by Mike Taylor <mike@z3950.org>
	http://www.miketaylor.org.uk
Please email me with bug-reports, wishlist items, patches, deployment
stories and, of course, large cash donations.


LICENCE
-------

This software is Open Source, but I've not yet decided exactly what
licence to use.  Be good.  Assume I'm going with the GPL (most
restrictive) until I say otherwise.  For what it's worth, I think the
most likely licence is the LGPL (GNU's Lesser General Public Licence)
which lets you deploy cql-java as a part of a non-free larger work.


SEE ALSO
--------

Adam Dickmeiss's CQL compiler, written in C.
Rob Sanderson's CQL compiler, written in Python.
All the other free CQL compilers everyone's going to write  :-)


THINGS TO DO
------------

* ### Fix bug where "9x" is parsed as two tokens, a TT_NUMBER followed
  by a TT_WORD.  The problem here is that I don't think it's actually
  possible to fix this without throwing out StreakTokenizer and
  rolling our own, which we absolutely _don't_ want to do.

* Some niceties for the cql-decompiling back-end:
	* don't emit redundant parentheses.
	* don't put spaces around relations that don't need them.

* Write the PQN-generating back-end.  This will need to be driven from
  a configuation file specifying how to represent the qualifiers,
  relations, relation modifiers and wildcard characters as z39.50
  attributes.  I think Ray has such a thing, though perhaps not yet in
  a form sufficiently rigorous to be computer-readable.

* Consider the utility of yet another back-end that translates a
  CQLNode tree into a Type-1 query tree using the JZKit data
  structures.  That would be nice so that CQL could become a JZKit
  query-type; but you could achieve the same effect by generating PQN,
  and running that through JZKit's existing PQN-to-Type-1 compiler.

* Many refinements to the random query generator:
	* Generate relation modifiers
	* Proximity support
	* Don't always generate qualifier/relation for terms
	* Better selection of qualifier (configurable?)
	* Better selection of terms (from a dictionary file?)
	* Introduce wildcard characters into generated terms
	* Generate multi-word terms

* Write fuller "javadoc" comments.