NAME

       DBIx::DBStag::Constraint - recursive structure for representing query constraints

SYNOPSIS

DESCRIPTION

       A constraint is a recursive structure for representing query constraints;

         AND ---  x=1
           \
            \---- OR   ---  y>2
                   \
                    \-----  boolfunc(z)

       A constraint is either a bool (AND, OR, NOT) with >0 children, or it can be a leaf node
       representing an atomic constraint

       the constraint corresponds to a SQLTemplate option block; eg

         [ name LIKE &name& ]
         [ name => &name& ]
         [ start > &min_start& ]
         [ start => &start& ]
         [ somefunc(&x&) ]
         [ somefunc(&x&, &y&) ]
         [ somefunc(t.col, &x&, &y&) => &z& ]

       the constraint consists of an operator (represented by => in the option block). If no =>
       is present, then it is a simple variable binding.

       A constraint can consist of multiple variable bindings

WEBSITE

       <http://stag.sourceforge.net>

AUTHOR

       Chris Mungall <cjm@fruitfly.org>

COPYRIGHT

       Copyright (c) 2003 Chris Mungall

       This module is free software.  You may distribute this module under the same terms as perl
       itself