Third normal form (3NF) is a database schema design approach for relational databases which uses normalizing principles to reduce the duplication of data, avoid data anomalies, ensure referential integrity, and simplify data management. It was defined in 1971 by Edgar F. Codd, an English computer scientist who invented the relational model for database management.
A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely the primary key. Codd defined this as a relation in second normal form where all non-prime attributes depend only on the candidate keys and do not have a transitive dependency on another key.
A hypothetical example of a failure to meet third normal form would be a hospital database having a table of patients which included a column for the telephone number of their doctor. The phone number is dependent on the doctor, rather than the patient, thus would be better stored in a table of doctors. The negative outcome of such a design is that a doctor's number will be duplicated in the database if they have multiple patients, thus increasing both the chance of input error and the cost and risk of updating that number should it change (compared to a third normal form-compliant data model that only stores a doctor's number once on a doctor table).
Codd later realized that 3NF did not eliminate all undesirable data anomalies and developed a stronger version to address this in 1974, known as Boyce–Codd normal form.
- "Third Normal Form" | 2023-09-28 | 10 Upvotes 2 Comments
In the United States, a heckler's veto is a situation in which a party who disagrees with a speaker's message is able to unilaterally trigger events that result in the speaker being silenced. For example, a heckler can disrupt a speech to the point that the speech is canceled.
In the legal sense, a heckler's veto occurs when the speaker's right is curtailed or restricted by the government in order to prevent a reacting party's behavior. The common example is the termination of a speech or demonstration in the interest of maintaining the public peace based on the anticipated negative reaction of someone opposed to that speech or demonstration.
The term heckler's veto was coined by University of Chicago professor of law Harry Kalven. Colloquially, the concept is invoked in situations where hecklers or demonstrators silence a speaker without intervention of the law.
- "Heckler's Veto" | 2023-09-28 | 36 Upvotes 9 Comments
The Nuclear Engine for Rocket Vehicle Application (NERVA) was a nuclear thermal rocket engine development program that ran for roughly two decades. Its principal objective was to "establish a technology base for nuclear rocket engine systems to be utilized in the design and development of propulsion systems for space mission application". It was a joint effort of the Atomic Energy Commission (AEC) and the National Aeronautics and Space Administration (NASA), and was managed by the Space Nuclear Propulsion Office (SNPO) until the program ended in January 1973. SNPO was led by NASA's Harold Finger and AEC's Milton Klein.
NERVA had its origins in Project Rover, an AEC research project at the Los Alamos Scientific Laboratory (LASL) with the initial aim of providing a nuclear-powered upper stage for the United States Air Force intercontinental ballistic missiles. Nuclear thermal rocket engines promised to be more efficient than chemical ones. After the formation of NASA in 1958, Project Rover was continued as a civilian project and was reoriented to producing a nuclear powered upper stage for NASA's Saturn V Moon rocket. Reactors were tested at very low power before being shipped to Jackass Flats in the Nevada Test Site. While LASL concentrated on reactor development, NASA built and tested complete rocket engines.
The AEC, SNPO, and NASA considered NERVA a highly successful program in that it met or exceeded its program goals. It demonstrated that nuclear thermal rocket engines were a feasible and reliable tool for space exploration, and at the end of 1968 SNPO deemed that the latest NERVA engine, the XE, met the requirements for a human mission to Mars. It had strong political support from Senators Clinton P. Anderson and Margaret Chase Smith but was cancelled by President Richard Nixon in 1973. Although NERVA engines were built and tested as much as possible with flight-certified components and the engine was deemed ready for integration into a spacecraft, they never flew in space.
- "Nuclear Engine for Rocket Vehicle Application (Nerva)" | 2023-09-28 | 26 Upvotes 8 Comments
The prophetic perfect tense is a literary technique used in the Bible that describes future events that are so certain to happen that they are referred to in the past tense as if they had already happened.
- "Prophetic Perfect Tense" | 2023-09-28 | 145 Upvotes 90 Comments
"'No Way to Prevent This', Says Only Nation Where This Regularly Happens" is the title of a series of articles perennially published by the American news satire organization The Onion satirizing the frequency of mass shootings in the United States and the lack of action taken in the wake of such incidents.
Each article is about 200 words long, detailing the location of the shooting and the number of victims, but otherwise remaining essentially the same. A fictitious resident—usually of a state in which the shooting did not take place—is quoted as saying that the shooting was "a terrible tragedy", but "there's nothing anyone can do to stop them." The article ends by saying that the United States is the "only economically advanced nation in the world where roughly two mass shootings have occurred every month for the past eight years," and that Americans view themselves and the situation as "helpless".
- "'No Way to Prevent This,' Says Only Nation Where This Regularly Happens" | 2023-09-28 | 56 Upvotes 53 Comments
Archie R. McCardell (August 29, 1926 – July 10, 2008) was an American business leader. He was best known for his tenure as chief executive officer, president, and chairman of the board at the International Harvester farm and heavy equipment manufacturing concern from 1977 to 1982. Although Harvester was the nation's fourth-largest company at the time he assumed control, McCardell triggered a strike by unionized employees which ended disastrously for the company and led to its eventual demise.
- "New CEO took International Harvester from 4th largest US firm to bankruptcy" | 2023-09-25 | 32 Upvotes 14 Comments
Rhythm 0 was a six-hour work of performance art by Serbian artist Marina Abramović in Naples in 1974. The work involved Abramović standing still while the audience was invited to do to her whatever they wished, using one of 72 objects she had placed on a table. These included a rose, feather, perfume, honey, bread, grapes, wine, scissors, a scalpel, nails, a metal bar, a gun, and a bullet.
There were no separate stages. Abramović and the visitors stood in the same space, making it clear that the latter were part of the work. The purpose of the piece, she said, was to find out how far the public would go: "What is the public about and what are they going to do in this kind of situation?"
- "Rhythm 0" | 2023-09-25 | 385 Upvotes 269 Comments
On April 11, 2019, the Israeli spacecraft Beresheet crashed into the Moon during a failed landing attempt. Its payload included a few thousand tardigrades. Initial reports suggested they could have survived the crash landing. If any of them did survive, they would be the second animal species to reach the Moon, after humans.
We believe the chances of survival for the tardigrades... are extremely high.
The Hoxne Hoard ( HOK-sən) is the largest hoard of late Roman silver and gold discovered in Britain, and the largest collection of gold and silver coins of the fourth and fifth centuries found anywhere within the former Roman Empire. It was found by Eric Lawes, a metal detectorist in the village of Hoxne in Suffolk, England in 1992. The hoard consists of 14,865 Roman gold, silver, and bronze coins and approximately 200 items of silver tableware and gold jewellery. The objects are now in the British Museum in London, where the most important pieces and a selection of the rest are on permanent display. In 1993, the Treasure Valuation Committee valued the hoard at £1.75 million (about £3.79 million in 2021).
The hoard was buried in an oak box or small chest filled with items in precious metal, sorted mostly by type, with some in smaller wooden boxes and others in bags or wrapped in fabric. Remnants of the chest and fittings, such as hinges and locks, were recovered in the excavation. The coins of the hoard date it after AD 407, which coincides with the end of Britain as a Roman province. The owners and reasons for burial of the hoard are unknown, but it was carefully packed and the contents appear consistent with what a single very wealthy family might have owned. It is likely that the hoard represents only a part of the wealth of its owner, given the lack of large silver serving vessels and of some of the most common types of jewellery.
The Hoxne Hoard contains several rare and important objects, such as a gold body-chain and silver-gilt pepper-pots (piperatoria), including the Empress pepper pot. The hoard is also of particular archaeological significance because it was excavated by professional archaeologists with the items largely undisturbed and intact. The find helped to improve the relationship between metal detectorists and archaeologists, and influenced a change in English law regarding finds of treasure.
- "Hoxne Hoard" | 2023-09-22 | 67 Upvotes 31 Comments
The Carpet Makers (German original title: Die Haarteppichknüpfer), also published under the title The Hair Carpet Weavers, is a science fiction novel by German writer Andreas Eschbach, originally published in 1995. The first English language edition, released in 2005 by Tor Books, features a foreword by Orson Scott Card.
The book is set on a planet whose sole industry is weaving elaborate rugs. The carpets are made of human hair and require a lifetime of work to complete. The book is a series of inter-related stories that give increasingly more detail on the nature and purpose of the rugs and why the universe has tens of thousands of planets solely devoted to making such a thing, each thinking they are the only one.
There is a prequel to The Carpet Makers titled Quest (2001), which has not been translated into English so far.
- "The Carpet Makers" | 2023-09-21 | 26 Upvotes 4 Comments