##############################################################################
#
# Copyright (c) 2002 Nexedi SARL and Contributors. All Rights Reserved.
#                    Jean-Paul Smets-Solanes <jp@nexedi.com>
#
# WARNING: This program as such is intended to be used by professional
# programmers who take the whole responsability of assessing all potential
# consequences resulting from its eventual inadequacies and bugs
# End users who are looking for a ready-to-use solution with commercial
# garantees and support are strongly adviced to contract a Free Software
# Service Company
#
# This program is Free Software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#
##############################################################################

try:
    from Interface import Interface
except ImportError:
    # for Zope versions before 2.6.0
    from Interface import Base as Interface

class Predicate(Interface):
  """
    A Predicate allows to make a statement about a document.
    A statement can be related to:

    - the attributes of the document (ex. prix >= 3.0)

    - the categories of the document (ex. )

    The Predicate class is an abstract class, which is
    implemented by subclasses.
  """

  def test(self, context):
    """
      A Predicate can be tested on a given context
    """
    pass

  def asPythonExpression(self):
    """
      A Predicate can be rendered as a python expression. This
      is the preferred approach within Zope.
    """
    pass

  def asSqlExpression(self):
    """
      A Predicate can be rendered as an sql expression. This
      can be useful to create reporting trees based on the
      ZSQLCatalog
    """
    pass

