|
Archive@NYU >
Stern School of Business >
IOMS: Information Systems Working Papers >
Please use this identifier to cite or link to this item:
http://hdl.handle.net/2451/14245
|
| Title: | On Completeness of Historical Relational Query Languages |
| Authors: | Clifford, James
Croker, Albert
Tuzhilin, Alexander |
| Issue Date: | 24-Mar-1993 |
| Publisher: | Stern School of Business, New York University |
| Series/Report no.: | IS-93-08 |
| Abstract: | Numerous proposals for extending the relational data model to
incorporate the temporal dimension of data have appeared in the past
several years. These proposals have differed considerably in the way
that the temporal dimension has been incorporated both into the
structure of the extended relations of these temporal models, and
consequently into the extended relational algebra or calculus that they
define. Because of these differences it has been difficult to compare
the proposed models and to make judgments as to which of them might in
some sense be equivalent or even better. In this paper we define the
notions of temporally grouped and temporally ungrouped historical data
models and propose two notions of historical reIationa1 completeness,
analogous to Codd's notion of relational completeness, one for each type
of model. We show that the temporally ungrouped models are less
expressive than the grouped models, but demonstrate a technique for
extending the ungrouped models with a grouping mechanism to capture the
additional semantic power of temporal grouping. For the ungrouped models
we define three different languages, a temporal logic, a logic with
explicit reference to time, and a temporal algebra, and show that under
certain assumptions all three are equivalent in power. For the grouped
models we define a many-sorted logic with variables over ordinary
values, historical values, and times. Finally, we demonstrate the
equivalence of this grouped calculus and the ungrouped calculus extended
with a grouping mechanism. We believe the classification of historical
data models into grouped and ungrouped provides a useful framework for
the comparison of models in the literature, and furthermore the
exposition of equivalent languages for each type provides reasonable
standards for common, and minimal, notions of historical relational completeness. |
| URI: | http://hdl.handle.net/2451/14245 |
| Appears in Collections: | IOMS: Information Systems Working Papers
|
All items in Faculty Digital Archive are protected by copyright, with all rights reserved.
|
