Tripod: A Comprehensive Model for Spatial and Aspatial Historical Objects

Abstract

Spatio-temporal extensions to data models have been an active area of research for a number of years. To date, much of this work has focused on the relational data model, with object data models receiving far less consideration. This paper presents a spatio-historical object model that uses a specialized mechanism, called a history, to maintain knowledge about entities that change over time. Key features of the resulting proposal include: (i) consistent representations of primitive spatial and temporal types; (ii) a component-based design in which spatial, temporal and historical extensions are formalized incrementally, for subsequent use together or separately; (iii) a formally specified data model. The model can be used directly during the design of spatio-historical applications, but also forms the basis of an implementation activity developing a spatio-historical object database management system.

The Tripod spatio-historical data model

“…language bindings can be found in [18]. When the state of a database needs to be queried, developers can either write native language application programs or can issue declarative OQL queries.…”

“…This capability allows objects to be de/reactivated within a particular database, as opposed to being simply created and deleted. For example, our crime application can create a new block object b1:Block to exist during the time period [10][11][12][13][14][15][16][17][18][19][20], and to be subsequently (logically) deleted during the period [12][13][14][15]. The lifespan attribute for Block objects is internally defined as: historical ðTimeIntervals; DAYÞ attribute enum Status factive; inactiveg lifespan; which is populated in the example to give the history: b1:lifespan ¼ fh½10-12; 15-20Þ; activei; h½12-15Þ; inactiveig.…”

“…Tripod does provide an OQL (suitably extended with timestamp, spatial and historical constructs), but its discussion is outside the scope of this paper (see [10,[15][16][17] for further details). It is also possible to retrieve data through the databaseÕs language bindings (i.e., C++).…”

Spatio-temporal database support for long-period scientific data

“…For example, the work of (Bohlen, Jensen, & Skjellaug, 1998) falls into this category, as it extends SQL-92 by adding features from the temporal and spatial domain with the special focus on upward-compatibility between the new model and SQL-92. The Tripod project aims at extending the ODMG standard for object models with spatio-temporal capabilities (Griffiths, Fernandes, Paton, Mason, Huang, Worboys, Johnson, & Stell, 2001). The intended system is targeted at discrete changes, modelled as so-called histories.…”

A generic algorithmic framework for aggregation of spatio-temporal data

“…Although the results reported in this paper have broader applicability, they have been worked out in detail and implemented in the context of Tripod [5,6], a prototype spatiotemporal object-oriented DBMSs. Tripod comes equipped with set-based spatial and timestamp data types over which a specialized mechanism, called a history, is defined.…”