Temporal and real-time databases: a survey

Abstract

A temporal database contains time-varying data. In a real-time database transactions have deadlines or timing constraints. In this paper we review the substantial research in these two previously separate areas. First we characterize the time domain; then we investigate temporal and real-time data models. We evaluate temporal and real-time query languages along several dimensions. We examine temporal and real-time DBMS implementation. Finally, we summarize major research accomplishments to date and list several unanswered research questions. Index Terms-Object-oriented databases, relational databases, query languages, temporal data models, time-constrained databases, transaction time, user-defined time, valid time.

A Tale of Two Schemas: Creating a Temporal XML Schema from a Snapshot Schema with τXSchema

“…Currently there is no separation of elements or attributes based on the relative frequency of update. In the situation that some elements (for example) vary at a significantly different rate than other elements, it may prove more efficient to split the schema up into pieces such that elements with similar "rates of change" are together [25,29,32]. This would avoid redundant repetition of elements that do not change as frequently.…”

“…Indeed, that has been the approach taken by many researchers for the relational and object-oriented models [25,29,32]. As we will discuss in detail, that approach inherently introduces difficulties with respect to document validation, data independence, tool support, and standardization.…”

Query Processing Using Negative and Temporal Tuples in Stream Query Engines

“…In StreamAPAS, we develop a stream database which adapts the basis of relational databases and temporal databases [12,13,14] because they are also oriented towards processing ordered data. In contrast to other systems, our system processes both temporal positive tuples and the negative ones in a unitemporal stream model.…”

Quality-aware sensor data collection

“…Current sensor systems support a basic form of time constraints -data collection frequency as in TAG [Madden et al (2003)] and Cougar [Demers et al (2003)]. It is worthwhile to investigate other timing notions used in temporal, real-time databases [Ozsoyoglu and Snodgrass (1995); Ramamritham (1996);Tansel et al (1994)] and active databases [Chakravarthy et al (1994); Sistla and Wolfson (1995)], and then develop a variety of timing semantics appropriate for distributed sensor environments.…”