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Documents authored by Dyreson, Curtis E.

Document
DOI: 10.4230/LIPIcs.TIME.2023.13
Optimization of Nonsequenced Queries Using Log-Segmented Timestamps

Authors: Curtis E. Dyreson

Published in: LIPIcs, Volume 278, 30th International Symposium on Temporal Representation and Reasoning (TIME 2023)

Abstract
In a period-timestamped, relational temporal database, each tuple is timestamped with a period. The timestamp records when the tuple is "alive" in some temporal dimension. Nonsequenced semantics is a query evaluation semantics that involves adding temporal predicates and constructors to a query. We show how to use log-segmented timestamps to improve the efficiency of temporal, nonsequenced queries evaluated using a non-temporal DBMS, i.e., a DBMS that has no special temporal indexes or query evaluation operators. A log-segmented timestamp divides the time-line into segments of known length. Any temporal period can be represented by a small number of such segments. The segments can be appended to a relation as additional columns. The advantage of log-segmented timestamps is that each segment can be indexed using standard database indexes, e.g., a B^+-tree. A query optimizer can use the indexes to generate a lower cost query evaluation plan. This paper shows how to rewrite a query to use the additional columns and evaluates the time cost benefits and space cost disadvantages.
Cite as

Curtis E. Dyreson. Optimization of Nonsequenced Queries Using Log-Segmented Timestamps. In 30th International Symposium on Temporal Representation and Reasoning (TIME 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 278, pp. 13:1-13:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{dyreson:LIPIcs.TIME.2023.13,
  author =	{Dyreson, Curtis E.},
  title =	{{Optimization of Nonsequenced Queries Using Log-Segmented Timestamps}},
  booktitle =	{30th International Symposium on Temporal Representation and Reasoning (TIME 2023)},
  pages =	{13:1--13:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-298-3},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{278},
  editor =	{Artikis, Alexander and Bruse, Florian and Hunsberger, Luke},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TIME.2023.13},
  URN =		{urn:nbn:de:0030-drops-191036},
  doi =		{10.4230/LIPIcs.TIME.2023.13},
  annote =	{Keywords: Temporal databases, nonsequenced semantics, query evaluation, query performance}
}
Document
DOI: 10.4230/LIPIcs.TIME.2021.14
Achieving a Sequenced, Relational Query Language with Log-Segmented Timestamps

Authors: Curtis E. Dyreson and M. A. Manazir Ahsan

Published in: LIPIcs, Volume 206, 28th International Symposium on Temporal Representation and Reasoning (TIME 2021)

Abstract
In a period-timestamped, relational temporal database, each tuple is timestamped with a period. The timestamp records when the tuple is "alive" in some temporal dimension. Sequenced semantics is a special semantics for evaluating a query in a temporal database. The semantics stipulates that the query must, in effect, be evaluated simultaneously in each time instant using the tuples alive at that instant. Previous research has proposed changes to the query evaluation engine to support sequenced semantics. In this paper we show how to achieve sequenced semantics without modifying a query evaluation engine. Our technique has two pillars. First we use log-segmented timestamps to record a tuple’s lifetime. A log-segmented timestamp divides the time-line into segments of known length. Any temporal period can be represented by a small number of such segments. Second, by taking advantage of the properties of log-segmented timestamps, we translate a sequenced relational algebra query to a non-temporal relational algebra query, using the operations already present in an unmodified, non-temporal query evaluation engine. The primary contribution of this paper is how to implement sequenced semantics using log-segmented timestamped tuples in a generic DBMS, which, to the best of our knowledge, has not been previously shown.
Cite as

Curtis E. Dyreson and M. A. Manazir Ahsan. Achieving a Sequenced, Relational Query Language with Log-Segmented Timestamps. In 28th International Symposium on Temporal Representation and Reasoning (TIME 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 206, pp. 14:1-14:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{dyreson_et_al:LIPIcs.TIME.2021.14,
  author =	{Dyreson, Curtis E. and Ahsan, M. A. Manazir},
  title =	{{Achieving a Sequenced, Relational Query Language with Log-Segmented Timestamps}},
  booktitle =	{28th International Symposium on Temporal Representation and Reasoning (TIME 2021)},
  pages =	{14:1--14:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-206-8},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{206},
  editor =	{Combi, Carlo and Eder, Johann and Reynolds, Mark},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TIME.2021.14},
  URN =		{urn:nbn:de:0030-drops-147900},
  doi =		{10.4230/LIPIcs.TIME.2021.14},
  annote =	{Keywords: Temporal databases, sequenced semantics, query evaluation, relational algebra}
}
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