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Please use this identifier to cite or link to this item:
http://hdl.handle.net/2451/14137
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| Title: | On Data Representation and Use In A Temporal Relational DBMS |
| Authors: | Clifford, James
Croker, Albert
Tuzhilin, Alexander |
| Issue Date: | 1995 |
| Publisher: | Stern School of Business, New York University |
| Series/Report no.: | IS-95-26 |
| Abstract: | Numerous proposals for extending the relational data model to
incorporate the temporal dimension of data have appeared over the past
decade. It has long been known that these proposals have adopted one of
two basic approaches to the incorporation of time into the extended
relational model. Recent work formally contrasted the expressive power
of these two approaches, termed temporally ungrouped and temporally
grouped, and demonstrated that the temporally grouped models are more
expressive. IN the temporally ungrouped models, the temporal dimension
is added through the addition of some number of distinguished attributes
to the schema of each relation, and each tuple is "stamped"
with temporal values for these attributes. By contrast, in temporally
grouped models the temporal dimension is added to the types of values
that serve as the domain of each ordinary attribute, and the
application's schema is left intact. The recent appearance of TSQL2, a
temporal extension to the SQL-92 standard based upon the temporally
ungrouped paradigm, means that it is likely that commercial DBMS's will
be extended to support time in this weaker way. Thus the distinction
between these two approaches - and its impact on the day-to-day user of
a DBMS - is of increasing relevance to the database practitioner and the
database user community. In this paper we address this issue from the
practical perspective of such a user. Through a series of example
queries and updates, we illustrate the differences between these two
approaches and demonstrate that the temporally grouped approach more
adequately captures the semantics of historical data. |
| URI: | http://hdl.handle.net/2451/14137 |
| Appears in Collections: | IOMS: Information Systems Working Papers
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