Historical Queries Research Articles

Graceful database schema evolution

Supporting graceful schema evolution represents an unsolved problem for traditional information systems that is further exacerbated in web information systems, such as Wikipedia and public scientific databases: in these projects based on multiparty cooperation the frequency of database schema changes has increased while tolerance for downtimes has nearly disappeared. As of today, schema evolution remains an error-prone and time-consuming undertaking, because the DB Administrator (DBA) lacks the methods and tools needed to manage and automate this endeavor by (i) predicting and evaluating the effects of the proposed schema changes, (ii) rewriting queries and applications to operate on the new schema, and (iii) migrating the database. Our PRISM system takes a big first step toward addressing this pressing need by providing: (i) a language of Schema Modification Operators to express concisely complex schema changes, (ii) tools that allow the DBA to evaluate the effects of such changes, (iii) optimized translation of old queries to work on the new schema version, (iv) automatic data migration, and (v) full documentation of intervened changes as needed to support data provenance, database flash back, and historical queries. PRISM solves these problems by integrating recent theoretical advances on mapping composition and invertibility, into a design that also achieves usability and scalability. Wikipedia and its 170+ schema versions provided an invaluable testbed for validating PRISM tools and their ability to support legacy queries.

Temporal queries and version management in XML-based document archives

By storing the successive versions of a document in an incremental fashion, XML repositories and data warehouses achieve: (i) the efficient preservation of critical information and (ii) the ability to support historical queries on the evolution of documents and their contents. In this paper, we present efficient techniques for managing multi-version document histories and supporting powerful temporal queries on such documents. Our approach consists of: (i) concisely representing the successive versions of a document as an XML document that implements a temporally-grouped data model and (ii) using XML query languages, such as XQuery, to express complex queries on the content of a particular version, and on the temporal evolution of the document elements and contents. We show that the data definition and manipulation framework of XML and XQuery can effectively support temporal models and historical queries without requiring extensions to the current standards; in fact, this approach is effective at representing and querying the histories of relational database tables, which are difficult to manage using SQL. These conclusions emerge through a number of interesting case studies presented in this paper that include W3C documents, the UCLA course catalog, and the CIA World Factbook.

Adaptive processing of historical spatial range queries in peer-to-peer sensor networks

We investigate the problem of processing historical queries on a sensor network. Since data is considered to have been already collected at the sensor nodes, the main issue is exploring the spatial component of the query in order to minimize its cost represented by the energy consumption. We assume queries can be issued at any network node, i.e., there is no central base station and all nodes have only local knowledge of the network. On the one hand, a globally optimum query processing plan is desirable but its construction is not possible due to the lack of global knowledge of the network. On the other hand, while a simple network flooding is feasible, it is not a practical choice from a cost perspective. To address this problem we propose a two-phase query processing strategy, where in the first phase a path from the query originator to the query region is found and in the second phase the query is processed within the query region itself. This strategy is supported by analytical models that are used to dynamically select the best processing strategy depending on the query specifics. Our extensive analytical and experimental results show that our analytical models are accurate and that the two-phase strategy is better suited for small to medium sized queries, being up to 10 times more cost effective than a typical network flooding. In addition, the dynamic selection of a query processing technique proved itself capable of always delivering at least as good performance as the most energy efficient strategy for all query sizes.

Gradient Boundary Detection for Time Series Snapshot Construction in Sensor Networks

In many applications of sensor networks, the sink needs to keep track of the history of sensed data of a monitored region for scientific analysis or supporting historical queries. We call these historical data a time series of value distributions or snapshots. Obviously, to build the time series snapshots by requiring all of the sensors to transmit their data to the sink periodically is not energy efficient. In this paper, we introduce the idea of gradient boundary and propose the gradient boundary detection (GBD) algorithm to construct these time series snapshots of a monitored region. In GBD, a monitored region is partitioned into a set of subregions and all sensed data in one subregion are within a predefined value range, namely, the gradient interval. Sensors located on the boundaries of the subregions are required to transmit the data to the sink and, then, the sink recovers all subregions to construct snapshots of the monitored area. In this process, only the boundary sensors transmit their data and, therefore, energy consumption is greatly reduced. The simulation results show that GBD is able to build snapshots with a comparable accuracy and has up to 40 percent energy savings compared with the existing approaches for large gradient intervals.

An XML-Based Approach to Publishing and Querying the History of Databases

There is much current interest in publishing and viewing databases as XML documents. The general benefits of this approach follow from the popularity of XML and the tool set available for visualizing and processing information encoded in this universal standard. In this paper, we explore the additional and unique benefits achieved by this approach on temporal database applications. We show that XML with XQuery can provide surprisingly effective solutions to the problem of supporting historical queries on past content of database relations and their evolution. Indeed, using XML, the histories of database relations can be naturally represented by temporally grouped data models. Thus, we identify mappings from relations to XML that are most conducive to modeling and querying database histories, and show that temporal queries that would be difficult to express in SQL can be easily expressed in standard XQuery. This approach is very general, insofar as it can be used to store the version history of arbitrary documents and, for relational databases, it also supports queries on the evolution of their schema. Then, we turn to the problem of supporting efficiently the storage and the querying of relational table histories. We present an experimental study of the pros and cons of using native XML databases, versus using traditional databases, where the XML-represented histories are supported as views on the historical tables.

Indexing spatiotemporal archives

Spatiotemporal objects – that is, objects that evolve over time – appear in many applications. Due to the nature of such applications, storing the evolution of objects through time in order to answer historical queries (queries that refer to past states of the evolution) requires a very large specialized database, what is termed in this article a spatiotemporal archive. Efficient processing of historical queries on spatiotemporal archives requires equally sophisticated indexing schemes. Typical spatiotemporal indexing techniques represent the objects using minimum bounding regions (MBR) extended with a temporal dimension, which are then indexed using traditional multidimensional index structures. However, rough MBR approximations introduce excessive overlap between index nodes, which deteriorates query performance. This article introduces a robust indexing scheme for answering spatiotemporal queries more efficiently. A number of algorithms and heuristics are elaborated that can be used to preprocess a spatiotemporal archive in order to produce finer object approximations, which, in combination with a multiversion index structure, will greatly improve query performance in comparison to the straightforward approaches. The proposed techniques introduce a query efficiency vs. space tradeoff that can help tune a structure according to available resources. Empirical observations for estimating the necessary amount of additional storage space required for improving query performance by a given factor are also provided. Moreover, heuristics for applying the proposed ideas in an online setting are discussed. Finally, a thorough experimental evaluation is conducted to show the merits of the proposed techniques.

Spatio-temporal GIS data model based on event semantics

There are mainly four kinds of models to record and deal with historical information. By taking them as reference, the spatio-temporal model based on event semantics is proposed. In this model, according to the way for describing an event, all the information are divided into five domains. This paper describes the model by using the land parcel change in the cadastral information system, and expounds the model by using five tables corresponding to the five domains. With the aid of this model, seven examples are given on historical query, trace back and recurrence. This model can be implemented either in the extended relational database or in the object-oriented database.

Managing data-based systems across releases using historical data dictionaries

Many software systems, especially data-based ones, can be partially specified using tabular meta-data, which are more amenable to machine manipulation and analysis than procedural code. For instance, it is easier to build tools to manipulate a data-base schema expressed in a normalized tabular form than the same schema written as Structured-Query-Language (SQL) code. A historical data dictionary (HDD) is a system for storing and processing meta-data spanning several releases of a software system. It is useful for historical queries, code generation, release planning, and design of procedures for transitioning a data-based system efficiently between releases. This paper describes the structure of an HDD and the technology transfer issues associated with introducing this technology into the maintenance processes for Lucent Technologies' AutoPACE® decision support system. The introduction of HDDs has led directly to significant improvements in system availability, product quality, lead-time, and programmer productivity.

Blessed are the peacemakers: Martin Luther King, Jr., eight white religious leaders, and the "Letter from Birmingham Jail"

S. JONATHAN BASS. Blessed Are Peacemakers: Martin Luther King, Jr., Eight White Religious Leaders, and Letter from Birmingham Jail. Baton Rouge, Louisiana: Louisiana State University Press, 2001. Pp. xiv ± 322, illustrations, bibliography, index. $39.95. According to S. Jonathan Bass, the purpose of this book is to tell history of Martin Luther King, Jr.'s 'Letter from Birmingham Jail.' To accomplish this task, Bass poses and answers five questions about letter and eight white clergymen who unwittingly inspired its writing when they petitioned Dr. King to wait until some other time to protest racist practices Birmingham, Alabama. The five questions are: Why and how it was written? How and where was it prepared and published? Who were eight white ministers addressed letter? What were their backgrounds? What do their careers tell us about white religious community during civil rights era? Although author does not acknowledge it, these five questions are not new. They are historic queries that a small army of scholars have repeatedly raised and answered varying ways and degrees since assassination of Dr. King 1968. Because of widespread attention these questions have received during past thirty-some years, we are compelled to ponder why Bass is raising them again. Is he simply doing what all good historians are trained to do and thus seeking to bring new light to our understanding of these historic questions? Or, does he have an agenda that is more subterranean than apparent? We do not have to speculate long here. In second paragraph of preface author says, in these pages I hope you will a and generally objective study of history of [Dr. King's] letter and of [eight] leading white church and synagogue leaders Alabama 1963. Although he leaves it unstated, Bass wants his readers to do a bit more than simply find his study balanced and objective. His subterranean goal seems to be to convince readers that eight clergy deserve a more elevated position than what scholars thus far have given them. Until now, most interpretations have portrayed clerics as either misinformed religionists who did not understand interrelationship between Gospel and social activism or covert defenders of Birmingham racism. Bass' hidden agenda is to remove raiment of ignorance or racism from these men and re-clothe them saintly robes of blessed peacemakers. To absolve eight clerics of charge of racism, Bass moves his study two directions. First, he brings forth heretofore largely unexamined papers and oral testimonies of eight clergy. He uses these sources to advance idea that men were innocent peacemaking moderates that have been unfairly judged by some historians. As he moves his plot along, he increasingly casts these clergy as wise proponents of a gradualist approach to resolution of racial problems 1963 Birmingham. He projects gradualist approach of clergy on race issues as reason they became trapped between two unyielding forces. These were status quo position of hardcore racists who were determined to maintain staid old Birmingham racism and impatience of Dr. King and his followers who were just as determined to immediately overthrow that anti-blackness. Throughout this study, author subtly and shrewdly lifts up gradualist position of eight clerics as being more realistic, if not honorable, than immediate position of Dr. …

A Spatio-Temporal Model for the Manipulation of Lineage Metadata

Nowadays one of the most successful applications of GIS is the management of a land-use cadastre. A lot of corporate GIS databases are in development, they support the legal management and distribution of cadastral maps. However, the propagation of geographical updates toward cadastral databases is still a methodological and technical problem to address in the context of large applications with many different users. This paper proposes a model based on lineage metadata that supports the management of geographical changes in the context of a corporate cadastre application. Geographical and cadastral changes are identified from an analysis of the French cadastre which acts as a case study for the development of our model. The lineage metadata model is based on the application of a direct acyclic graph that permits the management of the evolution of geographical objects and the generation of historical queries. The proposed model is specified and validated with the O_{2} object-oriented database management system.

A temporal approach to managing schema evolution in object database systems

The issues of schema evolution and temporal object models are generally considered to be orthogonal and are handled independently. However, to properly model applications that need incremental design and experimentation, the evolutionary histories of the schema objects should be traceable rather than corrective so that historical queries can be supported. In this paper we propose a method for managing schema changes, and propagating these changes to object instances by exploiting the functionality of a temporal object model. The result is a uniform treatment of schema evolution and temporal support for many object database management systems applications that require both.

SCDBR: An Automated Reasoner for Specifications of Database Updates

In this paper we describe SCDBR, a system that is able to reason automatically from specifications of database updates written in the situation calculus, a first–order language originally proposed by John McCarthy for reasoning about actions and change. The specifications handled by the system are written in the formalism proposed by Ray Reiter for solving the frame problem that appears when one expresses the effects on the database predicates of the execution of atomic transactions. SCDBR is written in PROLOG, and can solve several reasoning tasks, among others, it is able to derive the final specification from effect axioms, to answer queries to virtually updated databases, to check legality of transactions, to prove integrity constraints from the specification, to modify the specification in order to embed a desired integrity constraint, and to answer historical queries. For some of these tasks SCDBR can call other systems, like relational database systems, automated theorem provers, and constraint solvers.

Situation assessment and prediction in intelligence domains

We discuss a user-friendly system containing an operational suite of tools that support intelligence data processing, data visualization, historical analysis, situation assessment and predictive analysis. The tools facilitate the study of events as a function of time to determine situational patterns. To support this analysis, the system has various data displays (e.g., timelines, maps charts, and tables) a historical event database, query capabilities, and expert system tools. The expert system tools analyze temporal information, predict future events, and explain decisions visually and textually. The tools are currently installed in several military commands and intelligence agencies supporting analysis ranging from strategic C3 to counter drug.

Historical queries along multiple lines of time evolution

Traditional approaches to addressing historical queries assume asingle line of time evolution; that is, a system (database, relation) evolves over time through a sequence of transactions. Each transaction always applies to the unique, current state of the system, resulting in a new current state. There are, however, complex applications where the system's state evolves intomultiple lines of evolution. In general, this creates a tree (hierarchy) of evolution lines, where each tree node represents the time evolution of a particular subsystem. Multiple lines create novel historical queries, such asvertical orhorizontal historical queries. The key characteristic of these problems is that portions of the history are shared; answering historical queries should not necessitate duplication of shared histories as this could increase the storage requirements dramatically. Both the vertical and horizontal historical queries have two parts: a “search” part, where the time of interest is located together with the appropriate subsystem, and a reconstruction part, where the subsystem's state is reconstructed for that time. This article focuses on the search part; several reconstruction methods, designed for single evolution lines can be applied once the appropriate time of interest is located. For both the vertical and the horizontal historical queries, we present algorithms that work without duplicating shared histories. Combinations of the vertical and horizontal queries are possible, and enable searching in both dimensions of the tree of evolutions.

On specifying database updates

We address the problem of formalizing the evolution of a database under the effect of an arbitrary sequence of update transactions. We do so by appealing to a first-order representation language called the situation calculus, which is a standard approach in artificial intelligence to the formalization of planning problems. We formalize database transactions in exactly the same way as actions in the artificial intelligence planning domain. This leads to a database version of the frame problem in artificial intelligence. We provide a solution to the frame problem for a special, but substantial, class of update transactions. Using the axioms corresponding to this solution, we provide procedures for determining whether a given sequence of update transactions is legal, and for query evaluation in an updated database. These procedures have the desirable property that they appeal to theorem-proving only with respect to the initial database state. We next address the problem of proving properties true in all states of the database. It turns out that mathematical induction is required for this task, and we formulate a number of suitable induction principles. Among those properties of database states that we wish to prove are the standard database notions of static and dynamic integrity constraints. In our setting, these emerge as inductive entailments of the database. Finally, we discuss various possible extensions of the approach of this paper, including transaction logs and historical queries, the complexity of query evaluation, actualized transactions, logic programming approaches to updates, database views, and state constraints.

Time-based operators for relational algebra query languages

We present a new approach for historical relational algebra languages based upon generalized logic for Boolean and comparison operators and a temporal modification of the standard relational algebra operators. Historical versions of standard (snapshot) relational algebra operators based upon this generalized logic are presented. The temporal modification employs a logic that operates on sets of value/time-interval pairs and which can be applied to snapshot as well as historical databases. Our emphasis is that the generalized operators can be used to enrich existing historical query languages and to provide an easier and more natural time-based interface. Using the generalized operators, users can express their queries more naturally, succinctly and elegantly. Examples are presented which illustrate that the modified operators offer a good degree of flexibility in expressing different temporal requirements.

A Historical query language

A historical query language, hquel, is designed as a minimal extension to quel, which is the query language of the database management system ingres. In the underlying data model, each attribute value is stored along with the time interval over which the value is valid. hquel includes new range declarations, set theoretic expressions, and conditions. Aggregate functions of quel are also extended for historical data. A new clause, “when”, is added to aggregate function definition to make aggregation over the time dimension easier. Semantics of time is embedded within the quel semantics without any major modifications. hquel also manipulates set-valued attributes in N1NF relations.

Performance analysis of temporal queries

Temporal databases maintaining history data on line extend conventional databases with capabilities for historical queries and rollback operations. To analyze the performance of temporal queries on databases using various access methods, we propose a model that takes a temporal query and a database schema as input, and outputs the estimated I/O cost for the query on that database. The model consists of four transformations through a series of formal expressions characterizing all phases of query processing. We validate the model by comparing the I/O cost estimated from the model with the actual cost measured from a prototype temporal DBMS. Since conventional databases are a subset of temporal databases, the model can also be used to analyze the performance of conventional databases.

Africa and the Ideology of Eurafrica: Neo-Colonialism or Pan-Africanism?

This article is an inquiry into the major causes of the continued state of underdevelopment and dependency of Africa in spite of its enormous wealth and tremendous economic potential. It constitutes a follow-up to earlier, historical queries on the present state of African economies:

Historical Notes and Queries

Historical Notes and Queries