Decision time

Last updated

In temporal databases, decision time is the time when a decision was made about a fact stored in a database.[ citation needed ] It is used to keep a history of decisions about valid times.

Contents

In a database table, the start and end time of the decision time interval can be represented by adding two table columns. This interval is closed [ in the lower bound, and open at the upper bound ). When a decision has not been replaced, the end time of the decision is unknown, and it can thus be considered valid "until changed" or infinite (∞).

Valid time and decision time are ways of modeling data, and is not applicable for all types of data, [1] and transaction time is hence the most used temporal functionality. [1] The concept of decision time can for example be used in bitemporal databases (together with valid time instead of transaction time), or in tritemporal databases. [2]

History

The term decision time was coined by Mario Nascimento and Margaret Eich (1995). [3]

Although the ISO SQL standard has included support for "application-time period tables" (valid time tables) and "system-versioned tables" (transaction tables) since SQL:2011, it does however not include spesific clauses for decision time.

Comparison with valid time and transaction time

In a tritemporal database, [4] valid times are a history of valid time periods for facts stored in the database. The decision times are a history of decisions about validity times, and transaction times are again a history of decision times. Thus, transaction times are a history of meta-histories ("histories of histories").

Decision time is unconstrained in relationship to valid time, but it must be earlier than the transaction time. For example, the decision time can not be assigned a date in the future.

Example

The following is a list of real events that occurred between the 1964 and 1976 United States presidential elections:

DateDecision makerReal world event
1964-11-03 Electoral College Election of 1964
1968-11-05Electoral College Election of 1968
1972-11-07Electoral College Election of 1972
1973-10-10 Spiro Agnew Agnew resigns
1973-10-12 Richard Nixon Nixon nominates Ford
1973-12-06 Congress Congress confirms Ford
1974-08-09Richard Nixon Nixon resigns
1974-08-20 Gerald Ford Ford nominates Rockefeller
1974-12-19CongressCongress confirms Rockefeller
1976-11-02Electoral College Election of 1976

In this example, a constant 7-day delay is assumed between the decision time and the transaction time when the data is committed to the database. Given those conditions, the database would have contained the following information after the election in 1976:

ValidDecisionTransaction
PresidentViceFromToFromToFromTo
JohnsonHumphrey1965-01-201969-01-201964-11-03∞1964-11-10∞
NixonAgnew1969-01-201973-01-201968-11-05∞1968-11-12∞
NixonAgnew1973-01-201977-01-201972-11-07∞1972-11-141973-10-17
NixonAgnew1973-01-201977-01-201972-11-071973-10-101973-10-17∞
NixonAgnew1973-01-201973-10-101973-10-10∞1973-10-17∞
Nixon(Vacant)1973-10-101977-01-201973-10-10∞1973-10-171973-12-13
NixonFord∞1977-01-201973-10-12∞1973-10-191973-12-13
Nixon(Vacant)1973-10-101977-01-201973-10-101973-12-061973-12-13∞
Nixon(Vacant)1973-10-101973-12-061973-12-06∞1973-12-13∞
NixonFord∞1977-01-201973-10-121973-12-061973-12-13∞
NixonFord1973-12-061977-01-201973-12-06∞1973-12-131974-08-15
NixonFord1973-12-061977-01-201973-12-061974-08-081974-08-15∞
NixonFord1973-12-061974-08-091974-10-08∞1974-08-15∞
Ford(Vacant)1974-08-091977-01-201974-10-08∞1974-08-151974-12-26
FordRockefeller∞1977-01-201974-10-20∞1974-08-271974-12-26
Ford(Vacant)1974-08-091977-01-201974-10-081974-12-191974-12-26∞
Ford(Vacant)1974-08-091974-12-191974-12-19∞1974-12-26∞
FordRockefeller∞1977-01-201974-08-201974-12-191974-12-26∞
FordRockefeller1974-12-191977-01-201974-12-19∞1974-12-26∞
CarterMondale1977-01-201981-01-201976-11-02∞1976-11-09∞

Given the 7-day delayed table above, the question "who was president and vice president for the valid time of 1977-01-01" (which given the 7-day delay could provide data for 1976-12-25) would be:

See also

Related Research Articles

<span class="mw-page-title-main">Database</span> Organized collection of data in computing

In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database.

<span class="mw-page-title-main">PostgreSQL</span> Free and open-source object relational database management system

PostgreSQL, also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. PostgreSQL features transactions with atomicity, consistency, isolation, durability (ACID) properties, automatically updatable views, materialized views, triggers, foreign keys, and stored procedures. It is supported on all major operating systems, including Linux, FreeBSD, OpenBSD, macOS, and Windows, and handles a range of workloads from single machines to data warehouses or web services with many concurrent users.

Structured Query Language (SQL) is a domain-specific language used to manage data, especially in a relational database management system (RDBMS). It is particularly useful in handling structured data, i.e., data incorporating relations among entities and variables.

<span class="mw-page-title-main">IBM Db2</span> Relational model database server

Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON and XML. The brand name was originally styled as DB2 until 2017, when it changed to its present form.

A surrogate key in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data, unlike a natural key.

A temporal database stores data relating to time instances. It offers temporal data types and stores information relating to past, present and future time. Temporal databases can be uni-temporal, bi-temporal or tri-temporal.

In temporal databases, valid-time is the time period when an event happened or something was true in the real world, or more formally when a fact was valid in the modeled reality.

In temporal databases, transaction time is the time when some data has been loaded into a database. The time when a transaction is valid can be called the transaction time-period. It is a technical timeline controlled by a integration layer. More formally, it is the point-in-time during which a fact stored in the database is considered to be true.

A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database. For example, when a new record is added to the employees table, new records should also be created in the tables of the taxes, vacations and salaries. Triggers can also be used to log historical data, for example to keep track of employees' previous salaries.

The Access Database Engine is a database engine on which several Microsoft products have been built. The first version of Jet was developed in 1992, consisting of three modules which could be used to manipulate a database.

Sixth normal form (6NF) is a normal form used in relational database normalization which extends the relational algebra and generalizes relational operators to support interval data, which can be useful in temporal databases.

<span class="mw-page-title-main">Virtuoso Universal Server</span> Computer software

Virtuoso Universal Server is a middleware and database engine hybrid that combines the functionality of a traditional relational database management system (RDBMS), object–relational database (ORDBMS), virtual database, RDF, XML, free-text, web application server and file server functionality in a single system. Rather than have dedicated servers for each of the aforementioned functionality realms, Virtuoso is a "universal server"; it enables a single multithreaded server process that implements multiple protocols. The free and open source edition of Virtuoso Universal Server is also known as OpenLink Virtuoso. The software has been developed by OpenLink Software with Kingsley Uyi Idehen and Orri Erling as the chief software architects.

Real-time database has two meanings. The most common use of the term refers to a database system which uses streaming technologies to handle workloads whose state is constantly changing. This differs from traditional databases containing persistent data, mostly unaffected by time. When referring to streaming technologies, real-time processing means that a transaction is processed fast enough for the result to come back and be acted on right away. Such real-time databases are useful for assisting social media platforms in the removal of fake news, in-store surveillance cameras identifying potential shoplifters by their behavior/movements, etc.

Java Database Connectivity (JDBC) is an application programming interface (API) for the Java programming language which defines how a client may access a database. It is a Java-based data access technology used for Java database connectivity. It is part of the Java Standard Edition platform, from Oracle Corporation. It provides methods to query and update data in a database, and is oriented toward relational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in the Java virtual machine (JVM) host environment.

Richard Thomas Snodgrass is an American computer scientist and writer and is professor emeritus at the University of Arizona. He is best known for his work on temporal databases, query language design, query optimization and evaluation, storage structures, database design, and ergalics.

SQL:2011 or ISO/IEC 9075:2011 is the seventh revision of the ISO (1987) and ANSI (1986) standard for the SQL database query language. It was formally adopted in December 2011. The standard consists of 9 parts which are described in detail in SQL. The next version is SQL:2016.

The following is provided as an overview of and topical guide to databases:

The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.

Database scalability is the ability of a database to handle changing demands by adding/removing resources. Databases use a host of techniques to cope.

A distributed SQL database is a single relational database which replicates data across multiple servers. Distributed SQL databases are strongly consistent and most support consistency across racks, data centers, and wide area networks including cloud availability zones and cloud geographic zones. Distributed SQL databases typically use the Paxos or Raft algorithms to achieve consensus across multiple nodes.

References

  1. 1 2 Sehn, Tim (2023-08-07). "So you want a Temporal Database? | DoltHub Blog" . Retrieved 2024-02-10.
  2. ↑ "A SURVEY ON TEMPORAL DATA AND ITS RELATED CONCEPTS - S.SENTHILARASI, Research Scholar Department of Computer Science, Vels Institute of Science, Technology & Advanced Studies (VISTAS) Dr.S.Kamalakkannan, Associate Professor Department of Information Technology Vels Instituteof Science, Technology & Advanced Studies (VISTAS)".
  3. ↑ Mario A. Nascimento, Margaret H. Eich, “Decision Time in Temporal Databases”, In Proceedings of the Second International Workshop on Temporal Representation and Reasoning, 1995, pp. 157-162
  4. ↑ "Semantics of Temporal Models With Multiple Temporal Dimensions - Peter Kraft and Jens Otto Sørensen, Aarhus School of Business, Denmark" (PDF).
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.