8.4 Data Structures for the Location Tracking Server

The location tracking server requires the user to specify a tracking set name when the server is created. Based on this name, additional data structures are created.

• <TS_NAME>_TRACKING_REGIONS (region_id NUMBER, geometry MDSYS.SDO_GEOMETRY) is a table containing the tracking region polygons defined in the tracking set <TS_NAME>. Users must insert the polygons into this table after the server is created. All of the polygons must be geodetic (using SRID 8307) and two dimensional. The table has a primary key defined on the REGION_ID column.

• <TS_NAME>_TRACKER (object_id NUMBER, region_id NUMBER, queue_no NUMBER, alert_when VARCHAR2(2)) is a table whose entries map the relationship between an object and a region in which the object is tracked. The table has a primary key defined on the OBJECT_ID and REGION_ID columns. This table is managed using the TRACKER_MSG type; users should not update this table directly.

• <TS_NAME>_TRACKER_QUEUES(num_loc_queues NUMBER, num_trkr_queues NUMBER) is a table that holds queue information needed by the server. The server populates and maintains this table; users should never modify this table.

• <TS_NAME>_TRACKER_LOG (message_level VARCHAR2(1), message VARCHAR2(512), ts TIMESTAMP WITH TIMEZONE) is a table containing log messages generated by the server. Message level ‘I’ indicates an informational message, and message level ‘E’ indicates an error message. This table is not dropped when the tracking set is dropped. However, if a tracking set of the same name is then created, this table is truncated and reused by the new tracking set.

• <TS_NAME>_NOTIFICATIONS (object_id NUMBER, region_id NUMBER, time TIMESTAMP, x NUMBER, y NUMBER, state VARCHAR2(8)) is an auxiliary table provided to users to store messages from the notifications queue. The layout of columns in this table match that of the NOTIFICATION_MSG type. The X and Y columns are the coordinate that prompted the notification for object_id in region_id at the time. The STATE column shows if the point INSIDE or OUTSIDE the region. For tracking types INSIDE and OUTSIDE this value never changes. For tracking type TRANSITION this column is the state of the object at the time it generated the notification.

• <TS_NAME>_TRAJECTORY is an auxiliary table not currently used by the location tracking server.

In addition to these tables, the location tracking server also creates a set of Advanced Queuing (AQ) objects for managing the location, tracking and notification messages. All of the queues have a prefix of <TS_NAME>, for example. <TS_NAME>_TRACKER_Q_1 and <TS_NAME>_LOCATION_Q_1.