# 
# Copyright (C) 2007-2008  Camptocamp
#  
# This file is part of MapFish Server
#  
# MapFish Server is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#  
# MapFish Server 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 Lesser General Public License for more details.
#  
# You should have received a copy of the GNU Lesser General Public License
# along with MapFish Server.  If not, see <http://www.gnu.org/licenses/>.
#

__all__ = ['comparison', 'featureid', 'logical', 'spatial']

class Filter(object):
    def __init__(self):
        raise NotImplementedError('Filter cannot be instantiated')

    def to_sql_expr(self):
        raise NotImplementedError('to_sql_expr must be implemented')
