Design of Oracle spatial temporal Spatial Database

Requirements Prerequisite: The data changes 1~2 times each year, the software estimated life cycle 50 years.

Practice environment: Oracle Spatial.

Glossary: spatio-temporal objects, snapshots.

Spatio-Temporal object: The space and time range and its attribute information that a geographical goal experiences from birth to extinction. This is a concept that is abstracted for the convenience of processing spatio-temporal data, which is equivalent to the whole information object in the whole information model. In order to understand space-time objects, we take two-dimensional feature as an example. Two dimensional objects occupy a certain space in two-dimensional space, which is represented as a two-dimensional geometry, which is its geometrical property. If a time axis is added to the (x,y,t) coordinate system, and any space object is considered to be born and extinct, the two-dimensional feature occupies a certain three-dimensional space in the (x,y,t) coordinate system. We will take the two-dimensional features from the birth to the extinction of the space occupied by this time period, called "Space-Time object." Similarly, spatiotemporal objects can be extended to three-dimensional objects in the time dimension, that is, four-dimensional objects. The attribute information of spatio-temporal objects is a two-dimensional table.

Snapshot: The spatial range and attribute information occupied by a geographical target at a particular time, or the spatial range and corresponding attribute information occupied by space-time object at a particular time. For example, a map of the location of a hotel, size, this is a hotel snapshot. Because the hotel is born from a moment, and will perish in a moment, and in the birth and death, may also move or expand. So the map reflects just the state of the hotel at some point, so call it a snapshot of the hotel at a certain moment or a snapshot of the space-time object at a particular moment. Note that snapshots always correspond to a particular time, or they will lose the meaning of the snapshot. The snapshot's property information is a record in the spatio-Temporal object property Information table.

Design direction: Spatial data and attribute data are organized by the concept of spatio-temporal objects, which makes it possible to query and analyze the history of objects change. The process of the application layer shielding historical data is treated as one of the functions of database module.

Technical points:

1, the Oracle package variable session independence.

2, Dynamic View technology (based on the function of the view)

Each space-time object is described by multiple snapshot records. Each observation of the observer is based on a specific observation time. For example, an observer in the diagram should see snapshot 2 of Object one and snapshot 2 of object three, but not other snapshot records for object Two and object one or three. Object Two is not visible because object two has died out before the time of observation. The snapshot of object one is not visible 1 because an object with an updated observation data snapshot 2 can better approximate the state of object two at the current observation time.

Datasheet: Data table design based on the above concepts

Stored procedures: Take advantage of the session independence of package variables in Oracle to create the following basic stored procedures in the package: set the current observation time, get the current observation time, and use the current observation time and the incoming snap_time,snap_end parameter to determine whether the snapshot record is visible (SNAP_ Filter).

Views: A view built on the snapshot record table that filters the records in the table based on the storage function Snap_filter. The incoming parameter is: Snap_time,snap_end., the return value is visible for this snapshot.

SELECT Obj_id, Snap_time, Geom, Attr

From snapshot record table

WHERE Snap_Filter(Snap_time, Snap_end) > 0;

Triggers: Triggers on a view that enable application-tier users to insert, modify, and delete data in the view.