Geografic-Information-System/lib/python/temporal/abstract_space_time_dataset.py

"""!@package grass.temporal

@brief GRASS Python scripting module (temporal GIS functions)

Temporal GIS related functions to be used in temporal GIS Python library package.

Usage:

@code
import grass.temporal as tgis

...
@endcode

(C) 2008-2011 by the GRASS Development Team
This program is free software under the GNU General Public
License (>=v2). Read the file COPYING that comes with GRASS
for details.

@author Soeren Gebbert
"""
from abstract_dataset import *
from temporal_granularity import *

###############################################################################

class abstract_space_time_dataset(abstract_dataset):
    """Abstract space time dataset class

       This class represents a space time dataset. Convenient functions
       to select, update, insert or delete objects of this type in the SQL
       temporal database exists as well as functions to register or unregister
       raster maps.

       Parts of the temporal logic are implemented in the SQL temporal database,
       like the computation of the temporal and spatial extent as well as the
       collecting of metadata.
    """
    def __init__(self, ident):
	self.reset(ident)

    def get_new_instance(self, ident=None):
        """Return a new instance with the type of this class

           @param ident: The unique identifier of the new object
        """
        raise IOError("This method must be implemented in the subclasses")

    def get_new_map_instance(self, ident=None):
        """Return a new instance of a map dataset which is associated with the type of this class

           @param ident: The unique identifier of the new object
        """
        raise IOError("This method must be implemented in the subclasses")

    def get_map_register(self):
        """Return the name of the map register table"""
        raise IOError("This method must be implemented in the subclasses")

    def set_map_register(self, name):
        """Set the name of the map register table

        This table stores all map names which are registered in this space time dataset.

           @param name: The name of the register table
        """
        raise IOError("This method must be implemented in the subclasses")

    def set_initial_values(self, temporal_type, semantic_type, \
                           title=None, description=None):
        """Set the initial values of the space time dataset

           @param temporal_type: The temporal type of this space time dataset (absolute or relative)
           @param semantic_type: The semantic type of this dataset
           @param title: The title
           @param description: The description of this dataset
        """

        if temporal_type == "absolute":
            self.set_time_to_absolute()
        elif temporal_type == "relative":
            self.set_time_to_relative()
        else:
            core.fatal(_("Unknown temporal type \"%s\"") % (temporal_type))

        self.base.set_semantic_type(semantic_type)
        self.metadata.set_title(title)
        self.metadata.set_description(description)

    def get_semantic_type(self):
        """Return the semantic type of this dataset"""
        return self.base.get_semantic_type()

    def get_initial_values(self):
        """Return the initial values: temporal_type, semantic_type, title, description"""
        
        temporal_type = self.get_temporal_type()
        semantic_type = self.base.get_semantic_type()
        title = self.metadata.get_title()
        description = self.metadata.get_description()

        return temporal_type, semantic_type, title, description

    def get_granularity(self):
        """Return the granularity"""
        
        temporal_type = self.get_temporal_type()

        if temporal_type == "absolute":
            granularity   = self.absolute_time.get_granularity()
        elif temporal_type == "relative":
            granularity = self.relative_time.get_granularity()

        return granularity

    def set_granularity(self, granularity):

        temporal_type = self.get_temporal_type()
 
        if temporal_type == "absolute":
            self.set_time_to_absolute()
            self.absolute_time.set_granularity(granularity)
        elif temporal_type == "relative":
            self.set_time_to_relative()
            self.relative_time.set_granularity(granularity)
        else:
            core.fatal(_("Unknown temporal type \"%s\"") % (temporal_type))

    def get_map_time(self):
        """Return the type of the map time, interval, point, maixed or invalid"""
        
        temporal_type = self.get_temporal_type()

        if temporal_type == "absolute":
            map_time   = self.absolute_time.get_map_time()
        elif temporal_type == "relative":
            map_time   = self.relative_time.get_map_time()

        return map_time

    def print_temporal_relation_matrix(self, maps):
        """Print the temporal relation matrix of all registered maps to stdout

           The temproal relation matrix includes the temporal relations between
           all registered maps. The relations are strings stored in a list of lists.
           
           @param dbif: The database interface to be used
        """

        for i in range(len(maps)):
            reltations = ""
            count = 0
            for j in range(i + 1, len(maps)):
                relation = maps[j].temporal_relation(maps[i])

                # print maps[j].base.get_name(), maps[i].base.get_name(), relation
                if count == 0:
                    relations = relation
                else:
                    relations += "," + relation
                count += 1
                # Break if the the next map follows
                if relation == "follows":
                    break
                # Break if the the next map is after
                if relation == "after":
                    break
            if i < len(maps) - 1:    
                print maps[i].base.get_name(), relations    
            else:
                print maps[i].base.get_name()

    def get_temporal_relation_matrix(self, maps):
        """Return the temporal relation matrix of all registered maps as listof lists

           The map list must be ordered by start time

           The temproal relation matrix includes the temporal relations between
           all registered maps. The relations are strings stored in a list of lists.
           
           @param maps: a ordered by start_time list of map objects
        """

        matrix = []

        # Create the temporal relation matrix
        # Add the map names first
        row = []
        for map in maps:
            row.append(map.get_id())
        matrix.append(row)

        for mapA in maps:
            row = []
            for mapB in maps:
                row.append(mapA.temporal_relation(mapB))
            matrix.append(row)

        return matrix

    def count_temporal_types(self, maps):
        """Return the temporal type of the registered maps as dictionary

           The map list must be ordered by start time

           The temporal type can be:
           * point    -> only the start time is present
           * interval -> start and end time
           * invalid  -> No valid time point or interval found

           @param maps: A sorted (start_time) list of abstract_dataset objects
        """

        time_invalid = 0
        time_point = 0
        time_interval = 0

        tcount = {}
        for i in range(len(maps)):
            # Check for point and interval data
            if maps[i].is_time_absolute():
                start, end, tz = maps[i].get_absolute_time()
            if maps[i].is_time_relative():
                start, end = maps[i].get_relative_time()

            if start and end:
                time_interval += 1
            elif start and not end:
                time_point += 1
            else:
                time_invalid += 1

        tcount["point"] = time_point
        tcount["interval"] = time_interval
        tcount["invalid"] = time_invalid

        return tcount

    def count_gaps(self, maps):
        """Count the number of gaps between temporal neighbours
        
           @param maps: A sorted (start_time) list of abstract_dataset objects
           @return The numbers of gaps between temporal neighbours
        """

        gaps = 0

        # Check for gaps
        for i in range(len(maps)):
            if i < len(maps) - 1:
                relation = maps[i + 1].temporal_relation(maps[i])
                if relation == "after":
                    gaps += 1

        return gaps

    def count_temporal_relations(self, maps):
        """Count the temporal relations between the registered maps.

           The map list must be ordered by start time

           @param maps: A sorted (start_time) list of abstract_dataset objects
           @return A dictionary with counted temporal relationships
        """

        tcount = {}
        for i in range(len(maps)):
            # Check for point and interval data
            for j in range(i + 1, len(maps)):
                relation = maps[j].temporal_relation(maps[i])

                if tcount.has_key(relation):
                    tcount[relation] = tcount[relation] + 1
                else:
                    tcount[relation] = 1

                # Break if the the next map follows
                if relation == "follows":
                    break
                # Break if the the next map is after
                if relation == "after":
                    break

        return tcount

    def check_temporal_topology(self, maps=None, dbif=None):
        """Check the temporal topology

           Correct topology means, that time intervals are not overlap or
           that intervals does not contain other intervals. Equal time intervals or
           points of time are not allowed.

           The map list must be ordered by start time

           Allowed and not allowed temporal relationships for correct topology
           after      -> allowed
           before     -> allowed
           follows    -> allowed
           precedes   -> allowed

           equivalent -> not allowed
           during     -> not allowed
           contains   -> not allowed
           overlaps   -> not allowed
           overlapped -> not allowed
           starts     -> not allowed
           finishes   -> not allowed
           started    -> not allowed
           finished   -> not allowed

           @param maps: A sorted (start_time) list of abstract_dataset objects
           @return True if topology is correct
        """
        if maps == None:
            maps = get_registered_maps_as_objects(where=None, order="start_time", dbif=dbif)

        relations = self.count_temporal_relations(maps)

        map_time = self.get_map_time()

        if map_time == "interval" or map_time == "mixed":
            if relations.has_key("equivalent"):
                return False
            if relations.has_key("during"):
                return False
            if relations.has_key("contains"):
                return False
            if relations.has_key("overlaps"):
                return False
            if relations.has_key("overlapped"):
                return False
            if relations.has_key("starts"):
                return False
            if relations.has_key("finishes"):
                return False
            if relations.has_key("started"):
                return False
            if relations.has_key("finished"):
                return False
        elif map_time == "point":
            if relations.has_key("equivalent"):
                return False
        else:
            return False

        return True

    def get_registered_maps_as_objects_with_gaps(self, where=None, dbif=None):
        """Return all registered maps as ordered (by start_time) object list with 
           "gap" map objects (id==None) for temporal topological operations

           Gaps between maps are identified as maps with id==None

           The objects are initialized with the id and the temporal extent (temporal type, start time, end time).
           In case more map informations are needed, use the select() method for each listed object.

           @param where: The SQL where statement to select a subset of the registered maps without "WHERE"
           @param dbif: The database interface to be used

           In case nothing found None is returned
        """

        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        obj_list = []
        
        maps = self.get_registered_maps_as_objects(where, "start_time", dbif)

        if maps and len(maps) > 0:
            for i in range(len(maps)):
                obj_list.append(maps[i])
                # Detect and insert gaps
                if i < len(maps) - 1:
                    relation = maps[i + 1].temporal_relation(maps[i])
                    if relation == "after":
                        start1, end1 = maps[i].get_valid_time()
                        start2, end2 = maps[i + 1].get_valid_time()
                        end = start2
                        if end1:
                            start = end1
                        else:
                            start = start1

                        map = self.get_new_map_instance(None)

                        if self.is_time_absolute():
                            map.set_absolute_time(start, end)
                        elif self.is_time_relative():
                            map.set_relative_time(start, end)
                        obj_list.append(copy.copy(map))

        if connect == True:
            dbif.close()

        return obj_list

    def get_registered_maps_as_objects(self, where=None, order="start_time", dbif=None):
        """Return all registered maps as ordered object list for temporal topological operations

           The objects are initialized with the id and the temporal extent (temporal type, start time, end time).
           In case more map informations are needed, use the select() method for each listed object.

           @param where: The SQL where statement to select a subset of the registered maps without "WHERE"
           @param order: The SQL order statement to be used to order the objects in the list without "ORDER BY"
           @param dbif: The database interface to be used

           In case nothing found None is returned
        """

        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        obj_list = []
        
        rows = self.get_registered_maps("id,start_time,end_time", where, order, dbif)

        count = 0
        if rows:
            for row in rows:
                core.percent(count, len(rows), 1)
                map = self.get_new_map_instance(row["id"])
                if self.is_time_absolute():
                    map.set_absolute_time(row["start_time"], row["end_time"])
                elif self.is_time_relative():
                    map.set_relative_time(row["start_time"], row["end_time"])
                obj_list.append(copy.copy(map))
                count += 1

        core.percent(1, 1, 1)

        if connect == True:
            dbif.close()

        return obj_list

    def get_registered_maps(self, columns=None, where = None, order = None, dbif=None):
        """Return sqlite rows of all registered maps.
        
           In case columsn are not specified, each row includes all columns specified in the datatype specific view

           @param columns: Columns to be selected as SQL compliant string
           @param where: The SQL where statement to select a subset of the registered maps without "WHERE"
           @param order: The SQL order statement to be used to order the objects in the list without "ORDER BY"
           @param dbif: The database interface to be used

           In case nothing found None is returned
        """

        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        rows = None

        if self.get_map_register():
            # Use the correct temporal table
            if self.get_temporal_type() == "absolute":
                map_view = self.get_new_map_instance(None).get_type() + "_view_abs_time"
            else:
                map_view = self.get_new_map_instance(None).get_type() + "_view_rel_time"

            if columns:
                sql = "SELECT %s FROM %s  WHERE %s.id IN (SELECT id FROM %s)" % (columns, map_view, map_view, self.get_map_register())
            else:
                sql = "SELECT * FROM %s  WHERE %s.id IN (SELECT id FROM %s)" % (map_view, map_view, self.get_map_register())

            if where:
                sql += " AND %s" % (where)
            if order:
                sql += " ORDER BY %s" % (order)

            try:
                dbif.cursor.execute(sql)
                rows = dbif.cursor.fetchall()
            except:
                if connect == True:
                    dbif.close()
                core.error(_("Unable to get map ids from register table <%s>") % (self.get_map_register()))
                raise

        if connect == True:
            dbif.close()

        return rows

    def delete(self, dbif=None):
        """Delete a space time dataset from the temporal database

           This method removes the space time dataset from the temporal database and drops its map register table

           @param dbif: The database interface to be used
        """
        # First we need to check if maps are registered in this dataset and
        # unregister them

        core.verbose(_("Delete space time %s  dataset <%s> from temporal database") % (self.get_new_map_instance(ident=None).get_type(), self.get_id()))

        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        # SELECT all needed informations from the database
        self.select(dbif)

        core.verbose(_("Drop map register table: %s") %  (self.get_map_register()))
        if self.get_map_register():
            rows = self.get_registered_maps("id", None, None, dbif)
            # Unregister each registered map in the table
            if rows:
                num_maps = len(rows)
                count = 0
                for row in rows:
	            core.percent(count, num_maps, 1)
                    # Unregister map
                    map = self.get_new_map_instance(row["id"])
                    self.unregister_map(map, dbif)
                    count += 1
	        core.percent(1, 1, 1)
            try:
                # Drop the map register table
                sql = "DROP TABLE " + self.get_map_register()
                dbif.cursor.execute(sql)
                dbif.connection.commit()
            except:
                if connect == True:
                    dbif.close()
                core.error(_("Unable to drop table <%s>") % (self.get_map_register()))
                raise

        # Remove the primary key, the foreign keys will be removed by trigger
        self.base.delete(dbif)
        self.reset(None)

        if connect == True:
            dbif.close()
            
    def register_map(self, map, dbif=None):
        """ Register a map in the space time dataset.

            This method takes care of the registration of a map
            in a space time dataset.

            In case the map is already registered this function will break with a warning
            and return False

           @param dbif: The database interface to be used
        """
        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        if map.is_in_db(dbif) == False:
            dbif.close()
            core.fatal(_("Only maps with absolute or relative valid time can be registered"))

        core.verbose(_("Register %s map <%s> in space time %s dataset <%s>") %  (map.get_type(), map.get_id(), map.get_type(), self.get_id()))

        # First select all data from the database
        map.select(dbif)

        if not map.check_valid_time():
            core.fatal(_("Map <%s> has invalid time") % map.get_id())

        map_id = map.base.get_id()
        map_name = map.base.get_name()
        map_mapset = map.base.get_mapset()
        map_register_table = map.get_stds_register()

        #print "Map register table", map_register_table

        # Get basic info
        stds_name = self.base.get_name()
        stds_mapset = self.base.get_mapset()
        stds_register_table = self.get_map_register()

        #print "STDS register table", stds_register_table

        if stds_mapset != map_mapset:
            dbif.close()
            core.fatal(_("Only maps from the same mapset can be registered"))

        # Check if map is already registred
        if stds_register_table:
	    if dbmi.paramstyle == "qmark":
		sql = "SELECT id FROM " + stds_register_table + " WHERE id = (?)"
	    else:
		sql = "SELECT id FROM " + stds_register_table + " WHERE id = (%s)"
            dbif.cursor.execute(sql, (map_id,))
            row = dbif.cursor.fetchone()
            # In case of no entry make a new one
            if row and row[0] == map_id:
                if connect == True:
                    dbif.close()
                core.warning(_("Map <%s> is already registered.") % (map_id))
                return False

        # Create tables
        sql_path = get_sql_template_path()

        # We need to create the stmap raster register table bevor we can register the map
        if map_register_table == None:
            # Create a unique id
            uuid_rand = "map_" + str(uuid.uuid4()).replace("-", "")

            map_register_table = uuid_rand + "_" + self.get_type() + "_register"
            
            # Read the SQL template
            sql = open(os.path.join(sql_path, "map_stds_register_table_template.sql"), 'r').read()
            # Create the raster, raster3d and vector tables
            sql = sql.replace("GRASS_MAP", map.get_type())
            sql = sql.replace("MAP_NAME", map_name + "_" + map_mapset )
            sql = sql.replace("TABLE_NAME", uuid_rand )
            sql = sql.replace("MAP_ID", map_id)
            sql = sql.replace("STDS", self.get_type())
            try:
		if dbmi.__name__ == "sqlite3":
		    dbif.cursor.executescript(sql)
		else:
		    dbif.cursor.execute(sql)
            except:
                if connect == True:
                    dbif.close()
                core.error(_("Unable to create the space time %s dataset register table for <%s>") % \
                            (map.get_type(), map.get_id()))
                raise

            # Set the stds register table name and put it into the DB
            map.set_stds_register(map_register_table)
            map.metadata.update(dbif)
            
            core.verbose(_("Created register table <%s> for %s map <%s>") % \
                          (map_register_table, map.get_type(), map.get_id()))

        # We need to create the table and register it
        if stds_register_table == None:
            # Create table name
            stds_register_table = stds_name + "_" + stds_mapset + "_" + map.get_type() + "_register"
            # Read the SQL template
            sql = open(os.path.join(sql_path, "stds_map_register_table_template.sql"), 'r').read()
            # Create the raster, raster3d and vector tables
            sql = sql.replace("GRASS_MAP", map.get_type())
            sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
            sql = sql.replace("SPACETIME_ID", self.base.get_id())
            sql = sql.replace("STDS", self.get_type())

            sql_script = ""
            sql_script += "BEGIN TRANSACTION;\n"
            sql_script += sql
            sql_script += "\n"
            sql_script += "END TRANSACTION;"
            try:
		if dbmi.__name__ == "sqlite3":
		    dbif.cursor.executescript(sql_script)
		else:
		    dbif.cursor.execute(sql_script)
                dbif.connection.commit()
            except:
                if connect == True:
                    dbif.close()
                core.error(_("Unable to create the space time %s dataset register table for <%s>") % \
                            (map.get_type(), map.get_id()))
                raise

            # Set the map register table name and put it into the DB
            self.set_map_register(stds_register_table)
            self.metadata.update(dbif)

            core.verbose(_("Created register table <%s> for space time %s  dataset <%s>") % \
                          (stds_register_table, map.get_type(), self.get_id()))

        # Register the stds in the map stds register table
        # Check if the entry is already there
	if dbmi.paramstyle == "qmark":
	    sql = "SELECT id FROM " + map_register_table + " WHERE id = ?"
	else:
	    sql = "SELECT id FROM " + map_register_table + " WHERE id = %s"
        dbif.cursor.execute(sql, (self.base.get_id(),))
      	row = dbif.cursor.fetchone()

        # In case of no entry make a new one
        if row == None:
	    if dbmi.paramstyle == "qmark":
		sql = "INSERT INTO " + map_register_table + " (id) " + "VALUES (?)"
	    else:
		sql = "INSERT INTO " + map_register_table + " (id) " + "VALUES (%s)"
            #print sql
            dbif.cursor.execute(sql, (self.base.get_id(),))

        # Now put the raster name in the stds map register table
	if dbmi.paramstyle == "qmark":
	    sql = "INSERT INTO " + stds_register_table + " (id) " + "VALUES (?)"
	else:
	    sql = "INSERT INTO " + stds_register_table + " (id) " + "VALUES (%s)"
        #print sql
        dbif.cursor.execute(sql, (map_id,))

        if connect == True:
            dbif.close()
            
        return True

    def unregister_map(self, map, dbif = None):
        """Unregister a map from the space time dataset.

           This method takes care of the unregistration of a map
           from a space time dataset.

           @param map: The map object to unregister
           @param dbif: The database interface to be used
        """
        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        if map.is_in_db(dbif) == False:
            dbif.close()
            core.fatal(_("Unable to find map <%s> in temporal database") % (map.get_id()))

        core.verbose(_("Unregister %s map <%s>") % (map.get_type(), map.get_id()))

        # First select all data from the database
        map.select(dbif)
        map_id = map.base.get_id()
        map_register_table = map.get_stds_register()
        stds_register_table = self.get_map_register()

        # Check if the map is registered in the space time raster dataset
	if dbmi.paramstyle == "qmark":
	    sql = "SELECT id FROM " + map_register_table + " WHERE id = ?"
	else:
	    sql = "SELECT id FROM " + map_register_table + " WHERE id = %s"
        dbif.cursor.execute(sql, (self.base.get_id(),))
      	row = dbif.cursor.fetchone()

        # Break if the map is not registered
        if row == None:
            core.warning(_("Map <%s> is not registered in space time dataset") %(map_id, self.base.get_id()))
            if connect == True:
                dbif.close()
            return False

        # Remove the space time raster dataset from the raster dataset register
        if map_register_table != None:
	    if dbmi.paramstyle == "qmark":
		sql = "DELETE FROM " + map_register_table + " WHERE id = ?"
	    else:
		sql = "DELETE FROM " + map_register_table + " WHERE id = %s"
            dbif.cursor.execute(sql, (self.base.get_id(),))

        # Remove the raster map from the space time raster dataset register
        if stds_register_table != None:
	    if dbmi.paramstyle == "qmark":
		sql = "DELETE FROM " + stds_register_table + " WHERE id = ?"
	    else:
		sql = "DELETE FROM " + stds_register_table + " WHERE id = %s"
            dbif.cursor.execute(sql, (map_id,))

        if connect == True:
            dbif.close()
            
    def update_from_registered_maps(self, dbif = None):
        """This methods updates the spatial and temporal extent as well as
           type specific metadata. It should always been called after maps are registered
           or unregistered/deleted from the space time dataset.

           The update of the temporal extent checks if the end time is set correctly.
           In case the registered maps have no valid end time (None) the maximum start time
           will be used. If the end time is earlier than the maximum start time, it will
           be replaced by the maximum start time.

           An other solution to automate this is to use the diactivated trigger
           in the SQL files. But this will result in a huge performance issue
           in case many maps are registred (>1000).
           
           @param dbif: The database interface to be used
        """
        core.verbose(_("Update metadata, spatial and temporal extent from all registered maps of <%s>") % (self.get_id()))

        # Nothing to do if the register is not present
        if not self.get_map_register():
            return

        connect = False

        if dbif == None:
            dbif = sql_database_interface()
            dbif.connect()
            connect = True

        map_time = None

        use_start_time = False

        # Get basic info
        stds_name = self.base.get_name()
        stds_mapset = self.base.get_mapset()
        sql_path = get_sql_template_path()

        #We create a transaction
        sql_script = ""
        sql_script += "BEGIN TRANSACTION;\n"
        
        # Update the spatial and temporal extent from registered maps
        # Read the SQL template
        sql = open(os.path.join(sql_path, "update_stds_spatial_temporal_extent_template.sql"), 'r').read()
        sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
        sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
        sql = sql.replace("SPACETIME_ID", self.base.get_id())
        sql = sql.replace("STDS", self.get_type())

        sql_script += sql
        sql_script += "\n"

        # Update type specific metadata
        sql = open(os.path.join(sql_path, "update_" + self.get_type() + "_metadata_template.sql"), 'r').read()
        sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
        sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
        sql = sql.replace("SPACETIME_ID", self.base.get_id())
        sql = sql.replace("STDS", self.get_type())

        sql_script += sql
        sql_script += "\n"

        sql_script += "END TRANSACTION;"

	if dbmi.__name__ == "sqlite3":
	    dbif.cursor.executescript(sql_script)
	else:
	    dbif.cursor.execute(sql_script)
	    
        # Read and validate the selected end time
        self.select()

        if self.is_time_absolute():
            start_time, end_time, tz = self.get_absolute_time()
        else:
            start_time, end_time = self.get_relative_time()

        # In case no end time is set, use the maximum start time of all registered maps as end time
        if end_time == None:
            use_start_time = True
        else:
            # Check if the end time is smaller than the maximum start time
            if self.is_time_absolute():
                sql = """SELECT max(start_time) FROM GRASS_MAP_absolute_time WHERE GRASS_MAP_absolute_time.id IN
                        (SELECT id FROM SPACETIME_NAME_GRASS_MAP_register);"""
                sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
                sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
            else:
                sql = """SELECT max(start_time) FROM GRASS_MAP_relative_time WHERE GRASS_MAP_relative_time.id IN
                        (SELECT id FROM SPACETIME_NAME_GRASS_MAP_register);"""
                sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
                sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )

            dbif.cursor.execute(sql)
            row = dbif.cursor.fetchone()

            if row != None:
                # This seems to be a bug in sqlite3 Python driver
		if dbmi.__name__ == "sqlite3":
		    tstring = row[0]
		    # Convert the unicode string into the datetime format
		    if tstring.find(":") > 0:
			time_format = "%Y-%m-%d %H:%M:%S"
		    else:
			time_format = "%Y-%m-%d"

		    max_start_time = datetime.strptime(tstring, time_format)
		else:
		    max_start_time = row[0]

		if end_time < max_start_time:
		    use_start_time = True
		    
        # Set the maximum start time as end time
        if use_start_time:
            if self.is_time_absolute():
                sql = """UPDATE STDS_absolute_time SET end_time =
               (SELECT max(start_time) FROM GRASS_MAP_absolute_time WHERE GRASS_MAP_absolute_time.id IN
                        (SELECT id FROM SPACETIME_NAME_GRASS_MAP_register)
               ) WHERE id = 'SPACETIME_ID';"""
                sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
                sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
                sql = sql.replace("SPACETIME_ID", self.base.get_id())
                sql = sql.replace("STDS", self.get_type())
            elif self.is_time_relative():
                sql = """UPDATE STDS_relative_time SET end_time =
               (SELECT max(start_time) FROM GRASS_MAP_relative_time WHERE GRASS_MAP_relative_time.id IN
                        (SELECT id FROM SPACETIME_NAME_GRASS_MAP_register)
               ) WHERE id = 'SPACETIME_ID';"""
                sql = sql.replace("GRASS_MAP", self.get_new_map_instance(None).get_type())
                sql = sql.replace("SPACETIME_NAME", stds_name + "_" + stds_mapset )
                sql = sql.replace("SPACETIME_ID", self.base.get_id())
                sql = sql.replace("STDS", self.get_type())

	    if dbmi.__name__ == "sqlite3":
		dbif.cursor.executescript(sql)
	    else:
		dbif.cursor.execute(sql)

        # Count the temporal map types
        maps = self.get_registered_maps_as_objects(dbif=dbif)
        tlist = self.count_temporal_types(maps)

        if tlist["interval"] > 0 and tlist["point"] == 0 and tlist["invalid"] == 0:
            map_time = "interval"
        elif tlist["interval"] == 0 and tlist["point"] > 0 and tlist["invalid"] == 0:
            map_time = "point"
        elif tlist["interval"] > 0 and tlist["point"] > 0 and tlist["invalid"] == 0:
            map_time = "mixed"
        else:
            map_time = "invalid"

        # Compute the granularity

        if map_time != "invalid":
            # Smallest supported temporal resolution
            if self.is_time_absolute():
                gran = compute_absolute_time_granularity(maps)
            elif self.is_time_relative():
                gran = compute_absolute_time_granularity(maps)
        else:
            gran = None

        # Set the map time type and update the time objects
        if self.is_time_absolute():
            self.absolute_time.select(dbif)
            self.metadata.select(dbif)
            if self.metadata.get_number_of_maps() > 0:
                self.absolute_time.set_map_time(map_time)
                self.absolute_time.set_granularity(gran)
            else:
                self.absolute_time.set_map_time(None)
                self.absolute_time.set_granularity(None)
            self.absolute_time.update_all(dbif)
        else:
            self.relative_time.select(dbif)
            self.metadata.select(dbif)
            if self.metadata.get_number_of_maps() > 0:
                self.relative_time.set_map_time(map_time)
                self.relative_time.set_granularity(gran)
            else:
                self.relative_time.set_map_time(None)
                self.relative_time.set_granularity(None)
            self.relative_time.update_all(dbif)

        if connect == True:
            dbif.close()