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# $Header: /export/home/gjanee/bucket99/paradigms/RCS/Temporal_Constant.py,v 1.2 2004/02/25 00:17:19 gjanee Exp $

# SYNOPSIS
#
#     Temporal_Constant (table, idColumn, begin, end, cardinality)
#
#         table
#             A table to query, e.g., "holding".
#
#         idColumn
#             The table's object identifier column (i.e., the column
#             to be selected), e.g., "holding_id".
#
#         begin
#             The begin date of a date range, expressed as an integer
#             in the encoding YYYYMMDD.
#
#         end
#             The end date of a date range, expressed as an integer in
#             the encoding YYYYMMDD.
#
#         cardinality
#             A Cardinality object representing the cardinality of
#             'table'.  Should be Cardinality("1") or
#             Cardinality("1?").
#
# DESCRIPTION
#
#     Translates a temporal constraint to a constant TRUE or FALSE
#     depending on whether the constraint date range matches the
#     constant date range [begin, end].  A constraint that matches
#     results in the query
#
#         SELECT idColumn FROM table
#             WHERE 1 = 1
#
#     being returned.  Otherwise, the query
#
#         SELECT idColumn FROM table
#             WHERE 1 = 0
#
#     is returned.
#
#     Exceptions thrown:
#
#         none
#
# AUTHOR
#
#     Greg Janee
#     gjanee@alexandria.ucsb.edu
#
# HISTORY
#
#     $Log: Temporal_Constant.py,v $
#     Revision 1.2  2004/02/25 00:17:19  gjanee
#     Minor documentation fix.
#
#     Revision 1.1  2004/02/10 05:54:07  gjanee
#     Initial revision
#

import types

import edu.ucsb.adl.middleware
M = edu.ucsb.adl.middleware

import UniversalTranslator
UT = UniversalTranslator

class Temporal_Constant (UT.Paradigm):
    def __init__ (self, table, idColumn, begin, end, cardinality):
        UT.assertType(table, types.StringType)
        UT.assertType(idColumn, types.StringType)
        UT.assertType(begin, types.IntType)
        assert begin >= 101 and begin <= 99991231,\
            "invalid date: " + str(begin)
            # 101 means '0000-01-01' here
        UT.assertType(end, types.IntType)
        assert end >= 101 and end <= 99991231,\
            "invalid date: " + str(end)
        assert begin <= end, "invalid date range: begin > end"
        UT.assertType(cardinality, UT.Cardinality)
        self.table = table
        self.idColumn = idColumn
        self.begin = begin
        self.end = end
        self.cardinality = cardinality.clone()
        self.cardinality.nullable = 0
    def translateBucketAtomic (self, constraint, vocabularies):
        UT.assertType(constraint, M.Query.TemporalConstraint)
        assert constraint.getOperator() in UT.standardTemporalOperators,\
            "unsupported operator: " + constraint.getOperator()
        if constraint.getOperator() == "contains":
            x = self.begin <= constraint.getBegin() and\
                self.end >= constraint.getEnd()
        elif constraint.getOperator() == "is-contained-in":
            x = self.begin >= constraint.getBegin() and\
                self.end <= constraint.getEnd()
        elif constraint.getOperator() == "overlaps":
            x = self.end >= constraint.getBegin() and\
                self.begin <= constraint.getEnd()
        else:
            UT.unhandledCase()
        if x:
            return UT.constantTrueQuery(self.table, self.idColumn, "N/A",
                self.cardinality)
        else:
            return UT.constantFalseQuery(self.table, self.idColumn,
                self.cardinality)