Class (knowledge representation)

In knowledge representation, a class is a collection of individuals or objects. A class can be defined either by extension, or by intension, using what is called in some ontology languages like OWL. If we follow the Type–token distinction, the ontology is divided into individuals, who are real worlds objects, or events, and types, or classes, who are sets of real world objects. Class expressions or definitions gives the properties that the individuals must fulfill to be members of the class. Individuals that fulfill the property are called Instances.

Relationships

Instantiation

The instantiation relationship is a relation between objects and classes. We say that an object O, say Harry the eagle is an instance of a class, say Eagle. Harry the eagle has all the properties that we can attribute to an eagle, for example his parents were eagles, he's a bird, he's a meat eater and so on. It's a special kind of is a relationship. It's noted Concept assertion () in Description logics, a family of logic based on classes, class assertion

Doctor Who

Doctor Who is a British science-fiction television programme produced by the BBC from 1963 to the present day. The programme depicts the adventures of the Doctor, a Time Lord—a space and time-travelling humanoid alien. He explores the universe in his TARDIS, a sentient time-travelling space ship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Accompanied by companions, the Doctor combats a variety of foes, while working to save civilisations and help people in need.

The show is a significant part of British popular culture, and elsewhere it has become a cult television favourite. The show has influenced generations of British television professionals, many of whom grew up watching the series. The programme originally ran from 1963 to 1989. There was an unsuccessful attempt to revive regular production in 1996 with a backdoor pilot, in the form of a television film. The programme was relaunched in 2005 by Russell T Davies, who was showrunner and head writer for the first five years of its revival, produced in-house by BBC Wales in Cardiff. The first series of the 21st century featured Christopher Eccleston in the title role and was produced by the BBC. Series two and three had some development money contributed by the Canadian Broadcasting Corporation (CBC), which was credited as a co-producer.Doctor Who also spawned spin-offs in multiple media, including Torchwood (2006–2011) and The Sarah Jane Adventures (2007–2011), both created by Russell T Davies; K-9 (2009–2010); and a single pilot episode of K-9 and Company (1981). There also have been many spoofs and cultural references to the character in other media.

Class (set theory)

In set theory and its applications throughout mathematics, a class is a collection of sets (or sometimes other mathematical objects) that can be unambiguously defined by a property that all its members share. The precise definition of "class" depends on foundational context. In work on Zermelo–Fraenkel set theory, the notion of class is informal, whereas other set theories, such as Von Neumann–Bernays–Gödel set theory, axiomatize the notion of "proper class", e.g., as entities that are not members of another entity.

A class that is not a set (informally in Zermelo–Fraenkel) is called a proper class, and a class that is a set is sometimes called a small class. For instance, the class of all ordinal numbers, and the class of all sets, are proper classes in many formal systems.

Outside set theory, the word "class" is sometimes used synonymously with "set". This usage dates from a historical period where classes and sets were not distinguished as they are in modern set-theoretic terminology. Many discussions of "classes" in the 19th century and earlier are really referring to sets, or perhaps to a more ambiguous concept.

Enigma (1982 film)

Enigma is a 1982 Anglo-American drama film directed by Jeannot Szwarc and starring Martin Sheen, Sam Neill, Brigitte Fossey, and Kevin McNally. Based on Michael Barak's novel The Enigma, the film centers on a CIA agent that tries to infiltrate Soviet intelligence in order to stop a murderous plot.

Plot

Alex Holbeck (Martin Sheen) is recruited as a CIA agent. He is sent to East Berlin on a mission to steal an Enigma code scrambler. This is part of an attempt to stop the Russian assassination of five Soviet dissidents which is planned for Christmas Day. What Alex doesn't know is that the CIA already has a code scrambler. By stealing the scrambler in Berlin, they are trying to convince the Russians that they don't have it.

On arrival in Berlin, Alex finds that the KGB knows he is there. Alex must use numerous disguises and escape from a number of capture attempts. He seeks shelter with his former lover, Karen (Brigitte Fossey) before moving on as this is too dangerous for her. Karen and a number of Alex's other old friends are arrested and tortured by the police in an attempt to gain information about Alex's whereabouts. As he gets more desperate, Alex enlists Karen's help again: she seduces Dimitri Vasilikov (Sam Neill), the KGB man in charge of the hunt for Alex, in order to obtain information. In the end Dimitri catches Alex and Karen and finds the scrambler hidden in an exhibition artifact. As he is in love with Karen, he lets them go, however, keeping the scrambler which was in fact not needed. On Christmas Day the assassination attempt is successfully thwarted.

Enigma (2001 film)

Enigma is a 2001 espionage thriller film directed by Michael Apted from a screenplay by Tom Stoppard. The script was adapted from the novel Enigma by Robert Harris, about the Enigma codebreakers of Bletchley Park in the Second World War.

Although the story is highly fictionalised, the process of encrypting German messages during World War II and decrypting them with the Enigma is discussed in detail, and the historical event of the Katyn massacre is highlighted. It was the last film scored by John Barry.

Plot

The story, loosely based on actual events, takes place in March 1943, when the Second World War was at its height. The cryptanalysts at Bletchley Park, Buckinghamshire, have a problem: the Nazi U-boats have changed one of their code reference books used for Enigma machine ciphers, leading to a blackout in the flow of vital naval signals intelligence. The British cryptanalysts have cracked the "Shark" cipher once before, and they need to do it again in order to keep track of U-boat locations.

Stargate SG-1 (season 1)

The first season of the military science fiction television series Stargate SG-1 commenced airing on the Showtime channel in the United States on July 27, 1997, concluded on the same channel on March 6, 1998, and contained 22 episodes. The show itself is a spin off from the 1994 hit movie, Stargate written by Dean Devlin and Roland Emmerich. Stargate SG-1 re-introduced supporting characters from the film universe, such as Jonathan "Jack" O'Neill and Daniel Jackson and included new characters such as Teal'c, George Hammond and Samantha "Sam" Carter. The first season was about a military-science expedition team discovering how to use the ancient device, named the Stargate, to explore the galaxy. However, they encountered a powerful enemy in the film named the Goa'uld, which is bent on destroying Earth and all that oppose them.

Ratings Success

The 100-minute premiere "Children of the Gods", which aired on July 27, 1997 at 8 p.m, received Showtime's highest-ever ratings for a series premiere and ranked as the highest-rated original movie to premiere on Showtime in 3-1/2 years at the time. The show got a 10.5 rating in Showtime's approximately 12 million U.S. households, which equaled approximately 1.5 million homes in total. Season one regular cast members included Richard Dean Anderson, Amanda Tapping, Michael Shanks, Christopher Judge and Don S. Davis.