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Microkernel | Security | The security benefits of microkernels have been frequently discussed. In the context of security the minimality principle of microkernels is, some have argued, a direct consequence of the principle of least privilege, according to which all code should have only the privileges needed to provide required functionality. Minimality requires that a system's trusted computing base (TCB) should be kept minimal. As the kernel (the code that executes in the privileged mode of the hardware) has unvetted access to any data and can thus violate its integrity or confidentiality, the kernel is always part of the TCB. Minimizing it is natural in a security-driven design. | wiki:25699801 |
Microkernel | Security | Consequently, microkernel designs have been used for systems designed for high-security applications, including KeyKOS, EROS and military systems. In fact common criteria (CC) at the highest assurance level (Evaluation Assurance Level (EAL) 7) has an explicit requirement that the target of evaluation be "simple", an acknowledgment of the practical impossibility of establishing true trustworthiness for a complex system. Unfortunately, again, the term "simple" is misleading and ill-defined. At least the Department of Defense Trusted Computer System Evaluation Criteria introduced somewhat more precise verbiage at the B3/A1 classes: In 2018, a paper presented at the Asia-Pacific Systems Conference claimed that microkernels were demonstrably safer than monolithic kernels by investigating all published critical CVEs for the Linux kernel at the time. | wiki:25699802 |
Microkernel | Security | The study concluded that 40% of the issues could not occur at all in a formally verified microkernel, and only 4% of the issues would remain entirely unmitigated in such a system. | wiki:25699803 |
Microkernel | Third generation | More recent work on microkernels has been focusing on formal specifications of the kernel API, and formal proofs of the API's security properties and implementation correctness. The first example of this is a mathematical proof of the confinement mechanisms in EROS, based on a simplified model of the EROS API. More recently (in 2007) a comprehensive set of machine-checked proofs was performed of the properties of the protection model of , a version of L4. This has led to what is referred to as "third-generation microkernels", characterised by a security-oriented API with resource access controlled by capabilities, virtualization as a first-class concern, novel approaches to kernel resource management, and a design goal of suitability for formal analysis, besides the usual goal of high performance. | wiki:25699804 |
Microkernel | Third generation | Examples are Coyotos, , Nova, Redox and Fiasco.OC. In the case of seL4, complete formal verification of the implementation has been achieved, i.e. a mathematical proof that the kernel's implementation is consistent with its formal specification. This provides a guarantee that the properties proved about the API actually hold for the real kernel, a degree of assurance which goes beyond even CC EAL7. It was followed by proofs of security-enforcement properties of the API, and a proof demonstrating that the executable binary code is a correct translation of the C implementation, taking the compiler out of the TCB. Taken together, these proofs establish an end-to-end proof of security properties of the kernel. | wiki:25699805 |
Microkernel | Nanokernel | The term "nanokernel" or "picokernel" historically referred to: There is also at least one case where the term nanokernel is used to refer not to a small kernel, but one that supports a nanosecond clock resolution. | wiki:25699806 |
Multihull | Introduction | A multihull is a ship or boat with more than one hull, whereas a vessel with a single hull is a monohull. Multihull ships can be classified by the number of hulls, by their arrangement and by their shapes and sizes. | wiki:25699807 |
Multihull | Multihull history | The first multihull vessels were Austronesian canoes. The builders hollowed out logs to make canoes and stabilized them by attaching outriggers to prevent them from capsizing. This led in due course to the proa, catamaran, and trimaran. In Polynesian terminology the catamaran is a pair of "Vaka" held together by "Aka", whereas the trimaran is a central "Vaka", with "Ama" on each side, attached by "Aka". Catamarans and trimarans share the same terminology. Modern pioneers of multihull design include James Wharram (UK), Derek Kelsall (UK), Tom Lack (UK), Lock Crowther (Aust), Hedly Nicol (Aust), Malcolm Tennant (NZ), Jim Brown (USA), Arthur Piver (USA), Chris White (US), Ian Farrier (NZ), LOMOcean (NZ), and Dick Newick (USA). | wiki:25699808 |
Multihull | Multihull types | The vast majority of multihull sailboats are catamarans. Trimarans are less common, and proas are virtually unknown outside the South Pacific. | wiki:25699809 |
Multihull | Outrigger canoe & proa | An outrigger canoe is a canoe with a slender outrigger ("ama") attached by two or more struts ("akas"). This craft will normally be propelled by paddles. If the craft has a sail, it is known as a proa. While canoes and proas both derive stability from the outrigger, the proa has the greater need of the outrigger to counter the heeling effect of the sail. The difficulty with the proa is that the outrigger must be on the lee side to be effective, which means that a change of tack will need the sail to be rearranged. | wiki:25699810 |
Multihull | Catamaran | A catamaran is a vessel with twin hulls. Commercial catamarans began in 17th century England. Separate attempts at steam-powered catamarans were carried out by the middle of the 20th century. However, success required better materials and more developed hydrodynamic technologies. During the second half of the 20th century catamaran designs flourished. Nowadays, catamarans are used as racing, sailing, tourist and fishing boats. Cruising catamarans are becoming important in the holiday charter market. Some 70% of fast passenger RoRo ferries are catamarans. The hulls of a catamaran are typically connected by a bridgedeck, although some simpler cruising catamarans simply have a trampoline stretched between the crossbeams (or "akas"). | wiki:25699811 |
Multihull | Catamaran | Small beachable catamarans, such as the Hobie Cat, also have only a trampoline between the hulls. Catamarans have no ballast and their stability is derived from the width between the hulls. The distance between hulls is called the "transverse clearance", and the greater this distance, the more stable the catamaran will be. | wiki:25699812 |
Multihull | Trimaran | A trimaran is a vessel with three hulls. Unlike a catamaran where the hulls are mirror-images of each other, a trimaran is rather like a monohull with two slim outriggers. A trimaran has less accommodation space than a catamaran, but may be capable of even faster speeds. The trimaran has the widest range of interactions of wave systems generated by hulls at speed. The interactions can be favorable or unfavorable, depending on relative hull arrangement and speed. No authentic trimarans exist. Model test results and corresponding simulations provide estimates on the power of the full-scale ships. The calculations show possible advantages in a defined band of relative speeds. | wiki:25699813 |
Multihull | Trimaran | A new type of super-fast vessel, the "wave-piercing" trimaran (WPT) is known as an air-born unloaded (up to 25% of displacement) vessel, that can achieve twice the speed with a relative power. | wiki:25699814 |
Multihull | Four and five hulls | Some multihulls with four (quadrimaran) or five (pentamaran) hulls have been proposed; few have been built. A Swiss entrepreneur is attempting to raise €25 million to build a sail-driven quadrimaran that would use solar power to scoop plastic from the ocean; the project is scheduled for launch in 2020. A French manufacturer, Tera-4, produces motor quadrimarans which use aerodynamic lift between the four hulls to promote planing and reduce power consumption. Design concepts for vessels with two pair of outriggers have been referred to as pentamarans. The design concept comprises a narrow, long hull that cuts through waves. The outriggers then provide the stability that such a narrow hull needs. | wiki:25699815 |
Multihull | Four and five hulls | While the aft sponsons act as trimaran sponsons do, the front sponsons do not touch the water normally; only if the ship rolls to one side do they provide added buoyancy to correct the roll. BMT Group, a shipbuilding and engineering company in the UK, has proposed a fast cargo ship and a yacht using this kind of hull. | wiki:25699816 |
Multihull | SWATH multihulls | Multihull designs may have hull beams that are slimmer at the water surface ("waterplane") than underwater. This arrangement allows good wave-piercing, while keeping a buoyant hydrodynamic hull beneath the waterplane. In a catamaran configuration this is called a small waterplane area twin hull, or SWATH. While SWATHs are stable in rough seas, they have the drawbacks, compared with other catamarans, of having a deeper draft, being more sensitive to loading, and requiring more power because of their higher underwater surface areas. Triple-hull configurations of small waterplane area craft had been studied, but not built, as of 2008. | wiki:25699817 |
Multihull | Characteristics | Multihulls differ significantly from monohulls in a number of ways: | wiki:25699818 |
Multihull | Physical | Multihulls have a broader variety of hull and payload geometries. Compared to a monohull, they have a relatively large beam, deck area (upper and inner), above-water capacity, shallower draft (allowing operation in shallower water) but a limited payload. | wiki:25699819 |
Multihull | Stability | Early Austronesians discovered that round logs tied together into a raft were more stable than a single log. Hollowing out the logs further increased buoyancy and payload. Separating two logs by a pair of cross-members (or "akas") further increased stability. Spanning the intervening distance with a platform provides space for accommodation. Compared to monohulls, multihulls are much less prone to heeling (tilt); a sailing catamaran will rarely heel more than 5° whereas a monohull will frequently heel to 45°. This is particularly noticeable when running the wind; a monohull will roll incessantly, while a catamaran will remain upright. A catamaran's stable motion reduces seasickness and tiredness of the crew, making it safer and more suitable for family cruising. | wiki:25699820 |
Multihull | Stability | The stability also allows more efficient solar energy collection and radar operation. However, shorter multihulls may be more prone towards an uncomfortable motion called "hobby horsing", especially when lightly loaded. Being heavier (because of its ballast), a monohull's momentum will temporarily maintain progress if the wind drops, while a (lighter) multihull has less momentum and may be prone to going "in irons" when going about. (Multihulls need to keep the jib "aback" to complete the turn. However, multihull skippers will frequently choose to "gybe" instead, as gybing is much less of an event in a multihull than in a monohull. | wiki:25699821 |
Multihull | Stability | Multihulls "ghost" well under sail as they respond readily in light airs. | wiki:25699822 |
Multihull | Ballast | From the earliest times, monohulls (whether or not fitted with sails) were stabilized by carrying ballast (such as rocks) in the bilges; and all modern monohull yachts and ships still rely on ballast for stability. Naval architects arrange the vessel's centre of gravity to be well below the hull's metacenter. The low centre of gravity acts as a counterweight as the craft heels around its centre of buoyancy; that is, as a monohull heels, its ballast operates to restore it to its upright position. By contrast, a multihull's stability is derived from its width, and modern multihulls are much wider than earlier designs, with the beam sometimes more than half the LOA. | wiki:25699823 |
Multihull | Ballast | Should the weather hull lift from the water, the weight of the vessel will seek to restore the multihull to its normal position. However, unlike a monohull, a multihull has a "point of no return" which will lead to the vessel becoming inverted. A catamaran dinghy may be righted by its crew, but a large cruising cat will normally remain inverted unless it can be craned upright. A catamaran that is being pressed too hard may "pitchhole (capsize)", a disastrous event whereby the lee bow (downwind bow) digs into the water and trips, followed by the stern rising and the entire vessel somersaulting. | wiki:25699824 |
Multihull | Safety | Having no ballast, multihulls that become holed or inverted have a high rate of survivability; water-tight bulkheads should prevent sinking if the hulls fail. Catamarans may have increased reliability because most have an engine in each hulls. Whereas capsized monohulls typically right themselves, capsized multihulls remain inverted. Large multihulls may have escape hatches in the hulls or bridgedeck. | wiki:25699825 |
Multihull | Performance | Having a low displacement, and long, narrow hulls, a multihull typically produces very small bow waves and wakes, a consequence of a favorable Froude number. Vessels with beamy hulls (typically monohulls) normally create a large bow wave and wake. Such a vessel is limited by its "hull speed", being unable to "climb over" its bow wave unless it changes from displacement mode to planing mode. Vessels with slim hulls (typically multihulls) will normally create no appreciable bow wave to limit their progress. In 1978, 101 years after catamarans like "Amaryllis" were banned from yacht racing they returned to the sport. | wiki:25699826 |
Multihull | Performance | This started with the victory of the trimaran "Olympus Photo", skippered by Mike Birch in the first Route du Rhum. Thereafter, no open ocean race was won by a monohull. Winning times dropped by 70%, since 1978. Olympus Photo's 23-day 6 hr 58' 35" success dropped to Gitana 11's 7d 17h 19'6", in 2006. Around 2016 the first large wind driven foil-borne racing catamarans were built. These cats rise onto foils and T-foiled rudders only at higher speeds. | wiki:25699827 |
Multihull | Sailing multihulls and workboats | The increasing popularity of catamaran since the 1960s is down to the added space, speed, shallow draft, and lack of heeling underway. The stability of a multihull makes sailing much less tiring for the crew, and is particularly suitable for families. Having no need for ballast for stability, multihulls are much lighter than monohull sailboats; but a multihull's fine hull sections mean that one must take care not to overload the vessel. Powerboats catamarans are increasingly used for racing, cruising and as workboats and fishing boats. Speed, the stable working platform, safety, and added space are the prime advantages for power cats. | wiki:25699828 |
Multihull | Sailing multihulls and workboats | "The weight of a multihull, of this length, is probably not much more than half the weight of a monohull of the same length and it can be sailed with less crew effort." Racing catamarans and trimarans are popular in France, New Zealand and Australia. Cruising cats are commonest in the Caribbean and Mediterranean (where they form the bulk of the charter business) and Australia. Multihulls are less common in the US, perhaps because their increased beam require wider dock/slips. Smaller multihulls may be collapsible and trailerable, and thus suitable for daybooks and racers. Until the 1960s most multihull sailboats (except for beach cats) were built either by their owners or by boat builders; since then companies have been selling mass-produced boats, of which there are more than 150 models. | wiki:25699829 |
Multics Relational Data Store | Introduction | The Multics Relational Data Store, or MRDS for short, was the first commercial relational database management system. It was written in PL/1 by Honeywell for the Multics operating system and first sold in June 1976. Unlike the SQL systems that emerged in the late 1970s and early 80's, MRDS used a command language only for basic data manipulation, equivalent to the codice_1 or codice_2 statements in SQL. Other operations, like creating a new database, or general file management, required the use of a separate command program. | wiki:25699830 |
Mike Oldfield | Introduction | Michael Gordon Oldfield (born 15 May 1953) is an English musician, multi-instrumentalist and songwriter best known for his debut studio album "Tubular Bells" (1973), which became an unexpected critical and commercial success and propelled him to worldwide fame. Though primarily a guitarist, Oldfield is known for playing a range of instruments which include keyboards, percussion, and vocals. He has adopted a range of musical styles throughout his career, including progressive rock, world, folk, classical, electronic, ambient, and new age music. Oldfield took up the guitar at age ten and left school in his teens to embark on a music career. | wiki:25699831 |
Mike Oldfield | Introduction | From 1967 to 1970, he and his sister Sally Oldfield were a folk duo The Sallyangie, after which he performed with Kevin Ayers. In 1971, Oldfield started work on "Tubular Bells" which caught the attention of Richard Branson, who agreed to release it on his new label, Virgin Records. Its opening was used in the horror film "The Exorcist" and the album went on to sell over 2.7 million copies in the UK. Oldfield followed it with "Hergest Ridge" (1974), "Ommadawn" (1975), and "Incantations" (1978), all of which feature longform and mostly instrumental pieces. In the late 1970s, Oldfield began to tour and release more commercial and song-based music, beginning with "Platinum" (1979), "QE2" (1980), and "Five Miles Out" (1982). | wiki:25699832 |
Mike Oldfield | Introduction | His most successful album of this period was "Crises" (1983), which features the worldwide hit single "Moonlight Shadow" with vocalist Maggie Reilly. After signing with WEA in the early 1990s, Oldfield's most significant album of the decade was "Tubular Bells II" (1992) and experimented with virtual reality and gaming content with his MusicVR project. In 2012, he performed at the opening ceremony for the 2012 Olympic Games held in London. Oldfield's discography includes 26 studio albums, nine of which have reached the UK top-ten. His most recent album is "Return to Ommadawn" (2017). | wiki:25699833 |
Mike Oldfield | Early life | Oldfield was born on 15 May 1953 in Reading, Berkshire, to Raymond Oldfield, a general practitioner, and Maureen ("née" Liston), a nurse of Irish descent. He has two elder siblings, sister Sally and brother Terence. When Oldfield was seven his mother gave birth to a younger brother, David, but he had Down syndrome and died in infancy. His mother was prescribed barbiturates, to which she became addicted. She suffered from mental health problems and spent much of the rest of her life in mental institutions. She died in early 1975, shortly after Oldfield had started writing "Ommadawn". Oldfield attended St Joseph's Convent School, Highlands Junior School, St Edward's Preparatory School, and Presentation College, all in Reading. | wiki:25699834 |
Mike Oldfield | Early life | When he was thirteen the family moved to Harold Wood, then in Essex, and Oldfield attended Hornchurch Grammar School where, having already displayed musical talent, he earned one GCE qualification in English. Oldfield took up the guitar aged ten, first learning on a 6-string acoustic that his father gave him. He learned technique by copying parts from songs by folk guitarists Bert Jansch and John Renbourn that he played on a portable record player. He tried to learn musical notation but was a "very, very slow" learner; "If I have to, I can write things down. But I don't like to". | wiki:25699835 |
Mike Oldfield | Early life | By the time he was 12, Oldfield played the electric guitar and performed in local folk and youth clubs and dances, earning as much as £4 per gig. During a six-month break from music that Oldfield had around this time, he took up painting. In May 1968, when Oldfield turned fifteen, his school headmaster requested that he cut his long hair. Oldfield refused and left abruptly. He then decided to pursue music on a full-time, professional basis. | wiki:25699836 |
Mike Oldfield | 1968–1972: Early career | After leaving school Oldfield accepted an invitation from his sister Sally to form a folk duo The Sallyangie, taking its name from her name and Oldfield's favourite Jansch tune, "Angie". They toured England and Paris and struck a deal with Transatlantic Records, for which they recorded one album, "Children of the Sun" (1969). After they split in the following year Oldfield suffered a nervous breakdown. He auditioned as bassist for Family in 1969 following the departure of Ric Grech, but the group did not share Roger Chapman's enthusiasm towards Oldfield's performance. Oldfield spent much of the next year living off his father and performing in an electric rock band named Barefoot that included his brother Terry on flute, until the group disbanded in early 1970. | wiki:25699837 |
Mike Oldfield | 1968–1972: Early career | In February 1970, Oldfield auditioned as the bassist in The Whole World, a new backing band that former Soft Machine vocalist Kevin Ayers was putting together. He landed the position despite the bass being a new instrument for him, but he also played occasional lead guitar and later looked back on this time as providing valuable training on the bass. Oldfield went on to play on Ayers's albums "Shooting at the Moon" (1970) and "Whatevershebringswesing" (1971), and played mandolin on "Edgar Broughton Band" (1971). All three albums were recorded at Abbey Road Studios, where Oldfield familiarised himself with a variety of instruments, such as orchestral percussion, piano, Mellotron, and harpsichord, and started to write and put down musical ideas of his own. | wiki:25699838 |
Mike Oldfield | 1968–1972: Early career | While doing so Oldfield took up work as a reserve guitarist in a stage production of "Hair" at the Shaftesbury Theatre, where he played and gigged with Alex Harvey. After ten performances Oldfield grew bored of the job and was fired after he decided to play his part for "Let the Sunshine In" in 7/8 time. | wiki:25699839 |
Mike Oldfield | "Tubular Bells" | By mid-1971, Oldfield had assembled a demo tape containing sections of a longform instrumental piece initially titled "Opus One". Attempts to secure a recording deal to record it professionally came to nothing. In September 1971 Oldfield, now a session musician and bassist for the Arthur Louis Band, attended recording sessions at The Manor Studio near Kidlington, Oxfordshire, owned by businessman Richard Branson and run by engineers Tom Newman and Simon Heyworth. Branson already had several business ventures and was about to launch Virgin Records with Simon Draper. Newman and Heyworth heard some of Oldfield's demos and took them to Branson and Draper, who eventually gave Oldfield one week of recording time at The Manor, after which Oldfield had completed what became "Part One" of his composition, "Tubular Bells". | wiki:25699840 |
Mike Oldfield | "Tubular Bells" | He recorded "Part Two" from February to April 1973. Branson agreed to release "Tubular Bells" as the first record on the Virgin label and secured Oldfield a six-album deal with an additional four albums as optional. "Tubular Bells" was released on 25 May 1973. Oldfield played more than twenty different instruments in the multi-layered recording, and its style moved through diverse musical genres. Its 2,630,000 UK sales puts it at No. 34 on the list of the best-selling albums in the country. The title track became a top 10 hit single in the US after the opening was used in "The Exorcist" film in 1973. | wiki:25699841 |
Mike Oldfield | "Tubular Bells" | It is today considered to be a forerunner of the new-age music movement. | wiki:25699842 |
Mike Oldfield | "Hergest Ridge" to "Incantations" | In 1974, Oldfield played the guitar on the critically acclaimed album "Rock Bottom" by Robert Wyatt. In late 1974, his follow-up LP, "Hergest Ridge", was No. 1 in the UK for three weeks before being dethroned by "Tubular Bells". Although "Hergest Ridge" was released over a year after "Tubular Bells", it reached No. 1 first. "Tubular Bells" spent 11 weeks (10 of them consecutive) at No. 2 before its one week at the top. Like "Tubular Bells", "Hergest Ridge" is a two-movement instrumental piece, this time evoking scenes from Oldfield's Herefordshire country retreat. It was followed in 1975 by the pioneering world music piece "Ommadawn" released after the death of his mother Maureen. | wiki:25699843 |
Mike Oldfield | "Hergest Ridge" to "Incantations" | In 1975, Oldfield recorded a version of the Christmas piece "In Dulci Jubilo" which charted at No. 4 in the UK. | wiki:25699844 |
Mike Oldfield | "Platinum" to "Heaven's Open" | Oldfield's fifth album, "Platinum", was released in November 1979 and marked the start of his transition from long compositions towards mainstream and pop music. Oldfield performed across Europe between April and December 1980 with the In Concert 1980 tour. In 1980, Oldfield released "QE2", named after the ocean liner, which features a variety of guest musicians including Phil Collins on drums. This was followed by the European Adventure Tour 1981, during which Oldfield accepted an invitation to perform at a free concert celebrating the wedding of Prince Charles and Lady Diana in Guildhall. He wrote a new track, "Royal Wedding Anthem", for the occasion. | wiki:25699845 |
Mike Oldfield | "Platinum" to "Heaven's Open" | His next album, "Five Miles Out", followed in March 1982, which features the 24-minute track "Taurus II" occupying side one. The Five Miles Out World Tour 1982 saw Oldfield perform from April to December of that year. "Crises" saw Oldfield continue the pattern of one long composition with shorter songs. The first single from the album, "Moonlight Shadow", with Maggie Reilly on vocals, became Oldfield's most successful single, reaching No. 4 in the UK and No. 1 in nine other countries. The subsequent Crises Tour in 1983 concluded with a concert at Wembley Arena to commemorate the tenth anniversary of "Tubular Bells". | wiki:25699846 |
Mike Oldfield | "Platinum" to "Heaven's Open" | The next album, "Discovery", continues with this trend, being the first single "To France" and subsequent tour Discovery Tour 1984. | wiki:25699847 |
Mike Oldfield | 1992–2003: Warner years | By early 1992, Oldfield had secured Clive Banks as his new manager and had several record label owners listen to his demo of "Tubular Bells II" at his house. Oldfield signed with Rob Dickins of WEA Warner and recorded the album with Trevor Horn as producer. Released in August 1992, the album went to No. 1 in the UK. Its live premiere followed on 4 September at Edinburgh Castle which was released on home video as "Tubular Bells II Live". Oldfield supported the album with his Tubular Bells II 20th Anniversary Tour in 1992 and 1993, his first concert tour since 1984. | wiki:25699848 |
Mike Oldfield | 1992–2003: Warner years | By April 1993, the album had sold over three million copies worldwide. Oldfield continued to embrace new musical styles, with "The Songs of Distant Earth" (based on Arthur C. Clarke's novel of the same name) exhibiting a softer new-age sound. In 1994, he also had an asteroid, 5656 Oldfield, named after him. In 1995, Oldfield continued to embrace new musical styles by producing the Celtic-themed album "Voyager". In 1992, Oldfield met Luar na Lubre, a Galician Celtic-folk band (from A Coruña, Spain), with the singer Rosa Cedrón. The band's popularity grew after Oldfield covered their song "O son do ar" ("The sound of the air") on his "Voyager" album. | wiki:25699849 |
Mike Oldfield | 2004–present: Mercury years | On 12 April 2004 Oldfield launched his next virtual reality project, "Maestro", which contains music from the "Tubular Bells 2003" album and some new chillout melodies. The games have since been made available free of charge on Tubular.net. In 2005, Oldfield signed a deal with Mercury Records UK, who secured the rights to his catalogue when the rights had reverted back to himself. Mercury acquired the rights to Oldfield's back catalogue, in July 2007. Oldfield released his first album on the Mercury label, "Light + Shade", in September 2005. It is a double album of music of contrasting mood: relaxed (Light) and upbeat and moody (Shade). | wiki:25699850 |
Mike Oldfield | 2004–present: Mercury years | In 2006 and 2007, Oldfield headlined the Night of the Proms tour, consisting of 21 concerts across Europe. Also in 2007, Oldfield released his autobiography, "Changeling". In March 2008 Oldfield released his first classical album, "Music of the Spheres"; Karl Jenkins assisted with the orchestration. In the first week of release the album topped the UK Classical chart and reached number 9 on the main UK Album Chart. A single "Spheres", featuring a demo version of pieces from the album, was released digitally. The album was nominated for a Classical Brit Award, the NS&I Best Album of 2009. | wiki:25699851 |
Mike Oldfield | Musicianship | Although Oldfield considers himself primarily a guitarist, he is also one of popular music's most skilled and diverse multi-instrumentalists. His 1970s recordings were characterised by a very broad variety of instrumentation predominantly played by himself, plus assorted guitar sound treatments to suggest other instrumental timbres (such as the bagpipe, mandolin, "Glorfindel" and varispeed guitars on the original "Tubular Bells"). During the 1980s Oldfield became expert in the use of digital synthesizers and sequencers (notably the Fairlight CMI) which began to dominate the sound of his recordings: from the late 1990s onwards, he became a keen user of software synthesizers. He has, however, regularly returned to projects emphasising detailed, manually played and part-acoustic instrumentation (such as 1990's "Amarok", 1996's "Voyager" and 1999's "Guitars"). | wiki:25699852 |
Mike Oldfield | Musicianship | Oldfield has played over forty distinct and different instruments on record, including: While generally preferring the sound of guest vocalists, Oldfield has frequently sung both lead and backup parts for his songs and compositions. He has also contributed experimental vocal effects such as fake choirs and the notorious "Piltdown Man" impression on "Tubular Bells". | wiki:25699853 |
Mike Oldfield | Guitars | Over the years, Oldfield has used a range of guitars. Among the more notable of these are: Oldfield used a modified Roland GP8 effects processor in conjunction with his PRS Artist to get many of his heavily overdriven guitar sounds from the "Earth Moving" album onwards. Oldfield has also been using guitar synthesizers since the mid-1980s, using a 1980s Roland GR-300/G-808 type system, then a 1990s Roland GK2 equipped red PRS Custom 24 (sold in 2006) with a Roland VG8, and most recently a Line 6 Variax. Oldfield has an unusual playing style, using fingers and long right-hand fingernails and different ways of creating vibrato: a "very fast side-to-side vibrato" and "violinist's vibrato". | wiki:25699854 |
Mike Oldfield | Guitars | Oldfield has stated that his playing style originates from his musical roots playing folk music and the bass guitar. | wiki:25699855 |
Mike Oldfield | Keyboards | Over the years, Oldfield has owned and used a vast number of synthesizers and other keyboard instruments. In the 1980s, he composed the score for the film "The Killing Fields" on a Fairlight CMI. Some examples of keyboard and synthesised instruments which Oldfield has made use of include Sequential Circuits Prophet-5s (notably on "Platinum" and "The Killing Fields"), Roland JV-1080/JV-2080 units (1990s), a Korg M1 (as seen in the "Innocent" video), a Clavia Nord Lead and Steinway pianos. In recent years, he has also made use of software synthesis products, such as Native Instruments. | wiki:25699856 |
Mike Oldfield | Lead vocalists | Oldfield has occasionally sung himself on his records and live performances, sometimes using a vocoder as a resource. It is not unusual for him to collaborate with diverse singers and to hold auditions before deciding the most appropriate for a particular song or album. Featured lead vocalists who have collaborated with him include: | wiki:25699857 |
Mike Oldfield | Recording | Oldfield has self-recorded and produced many of his albums, and played the majority of the featured instruments, largely at his home studios. In the 1990s and 2000s he mainly used DAWs such as Apple Logic, Avid Pro Tools and Steinberg Nuendo as recording suites. For composing orchestral music Oldfield has been quoted as using the software notation program Sibelius running on Apple Macintoshes. He also used the FL Studio DAW on his 2005 double album "Light + Shade". Among the mixing consoles Oldfield has owned are an AMS Neve Capricorn 33238, a Harrison Series X, and a Euphonix System 5-MC. | wiki:25699858 |
Mike Oldfield | Personal life | Oldfield and his siblings were raised as Roman Catholics, their mother's faith. In his early life, Oldfield used drugs including LSD, whose effects on his mental health he discussed in his autobiography. During the early 1990s he underwent a course on mental health problems, and subsequently set up a foundation called Tonic, which sponsored people to have counselling and therapy. The trustee was the Professor of Psychiatry at Guy's Hospital, London. Oldfield has been married three times and has seven children. In 1978 he married Diana Fuller, a relative of the Exegesis group leader, which lasted for three months. Oldfield recalled that he phoned Branson the day after the ceremony and said he had made a mistake. | wiki:25699859 |
Mike Oldfield | Personal life | From 1979 to 1986, Oldfield was married to Sally Cooper, who he met through Virgin. They had three children, daughter Molly and sons Dougal (1981–2015) and Luke. Shortly before Luke's birth in 1986, the relationship had broken down and they amicably split. By this time, Oldfield had entered a relationship with Norwegian singer Anita Hegerland, lasting until 1991. The pair had met backstage at one of Oldfield's gigs while touring Germany in 1984. They lived in Switzerland, France, and England. They have two children: Greta and Noah. In the late 1990s, Oldfield posted in a lonely hearts column in a local Ibiza newspaper. | wiki:25699860 |
Mike Oldfield | Personal life | It was answered by Amy Lauer and the pair dated, but the relationship was troubled by Oldfield's bouts of alcohol and substance abuse and it ended after two months. In 2001, Oldfield began counselling and psychotherapy. Between 2002 and 2013, Oldfield was married to Fanny Vandekerckhove, who he had met while living in Ibiza. They have two sons, Jake and Eugene. Oldfield is a motorcycle fan and has five bikes. These include a BMW R1200GS, a Suzuki GSX-R750, a Suzuki GSX-R1000, and a Yamaha R1. He says that some of his inspiration for composing comes from riding them. Throughout his life Oldfield has also had a passion for building and flying model aircraft. | wiki:25699861 |
Mike Oldfield | Personal life | Since 1980, he has been a licensed pilot and has flown fixed wing aircraft (the first of which was a Beechcraft Sierra) and helicopters (including the Agusta Bell 47G, which featured on the sleeve of his cover version of the ABBA song "Arrival" as a pastiche of their album artwork). He is also interested in cars and has owned a Ferrari and a Bentley which was a gift from Richard Branson as an incentive for him to give his first live performance of "Tubular Bells". He has endorsed the Mercedes-Benz S-Class in the Mercedes UK magazine. Oldfield also considers himself to be a Trekkie. | wiki:25699862 |
Mike Oldfield | Personal life | He noted in an interview in 2008 that he had two boats. | wiki:25699863 |
Mike Oldfield | Awards and nominations | Grammy Awards Ivor Novello Awards NME Awards | wiki:25699864 |
Mutual recursion | Introduction | In mathematics and computer science, mutual recursion is a form of recursion where two mathematical or computational objects, such as functions or data types, are defined in terms of each other. Mutual recursion is very common in functional programming and in some problem domains, such as recursive descent parsers, where the data types are naturally mutually recursive. | wiki:25699865 |
Mutual recursion | Data types | The most important basic example of a data type that can be defined by mutual recursion is a tree, which can be defined mutually recursively in terms of a forest (a list of trees). Symbolically: A forest "f" consists of a list of trees, while a tree "t" consists of a pair of a value "v" and a forest "f" (its children). This definition is elegant and easy to work with abstractly (such as when proving theorems about properties of trees), as it expresses a tree in simple terms: a list of one type, and a pair of two types. | wiki:25699866 |
Mutual recursion | Data types | Further, it matches many algorithms on trees, which consist of doing one thing with the value, and another thing with the children. This mutually recursive definition can be converted to a singly recursive definition by inlining the definition of a forest: A tree "t" consists of a pair of a value "v" and a list of trees (its children). This definition is more compact, but somewhat messier: a tree consists of a pair of one type and a list of another, which require disentangling to prove results about. In Standard ML, the tree and forest data types can be mutually recursively defined as follows, allowing empty trees: | wiki:25699867 |
Mutual recursion | Computer functions | Just as algorithms on recursive data types can naturally be given by recursive functions, algorithms on mutually recursive data structures can be naturally given by mutually recursive functions. Common examples include algorithms on trees, and recursive descent parsers. As with direct recursion, tail call optimization is necessary if the recursion depth is large or unbounded, such as using mutual recursion for multitasking. Note that tail call optimization in general (when the function called is not the same as the original function, as in tail-recursive calls) may be more difficult to implement than the special case of tail-recursive call optimization, and thus efficient implementation of mutual tail recursion may be absent from languages that only optimize tail-recursive calls. | wiki:25699868 |
Mutual recursion | Computer functions | In languages such as Pascal that require declaration before use, mutually recursive functions require forward declaration, as a forward reference cannot be avoided when defining them. As with directly recursive functions, a wrapper function may be useful, with the mutually recursive functions defined as nested functions within its scope if this is supported. This is particularly useful for sharing state across a set of functions without having to pass parameters between them. | wiki:25699869 |
Mutual recursion | Basic examples | A standard example of mutual recursion, which is admittedly artificial, determines whether a non-negative number is even or odd by defining two separate functions that call each other, decrementing each time. In C: bool is_even(unsigned int n) { bool is_odd(unsigned int n) { | wiki:25699870 |
Mutual recursion | Advanced examples | A more complicated example is given by recursive descent parsers, which can be naturally implemented by having one function for each production rule of a grammar, which then mutually recurse; this will in general be multiple recursion, as production rules generally combine multiple parts. This can also be done without mutual recursion, for example by still having separate functions for each production rule, but having them called by a single controller function, or by putting all the grammar in a single function. Mutual recursion can also implement a finite-state machine, with one function for each state, and single recursion in changing state; this requires tail call optimization if the number of state changes is large or unbounded. | wiki:25699871 |
Mutual recursion | Advanced examples | This can be used as a simple form of cooperative multitasking. A similar approach to multitasking is to instead use coroutines which call each other, where rather than terminating by calling another routine, one coroutine yields to another but does not terminate, and then resumes execution when it is yielded back to. This allows individual coroutines to hold state, without it needing to be passed by parameters or stored in shared variables. There are also some algorithms which naturally have two phases, such as minimax (min and max), and these can be implemented by having each phase in a separate function with mutual recursion, though they can also be combined into a single function with direct recursion. | wiki:25699872 |
Mutual recursion | Mathematical functions | In mathematics, the Hofstadter Female and Male sequences are an example of a pair of integer sequences defined in a mutually recursive manner. Fractals can be computed (up to a given resolution) by recursive functions. This can sometimes be done more elegantly via mutually recursive functions; the Sierpiński curve is a good example. | wiki:25699873 |
Mutual recursion | Prevalence | Mutual recursion is very common in the functional programming style, and is often used for programs written in LISP, Scheme, ML, and similar languages. For example, Abelson and Sussman describe how a metacircular evaluator can be used to implement LISP with an eval-apply cycle. In languages such as Prolog, mutual recursion is almost unavoidable. Some programming styles discourage mutual recursion, claiming that it can be confusing to distinguish the conditions which will return an answer from the conditions that would allow the code to run forever without producing an answer. Peter Norvig points to a design pattern which discourages the use entirely, stating: | wiki:25699874 |
Mutual recursion | Terminology | Mutual recursion is also known as indirect recursion, by contrast with direct recursion, where a single function calls itself directly. This is simply a difference of emphasis, not a different notion: "indirect recursion" emphasises an individual function, while "mutual recursion" emphasises the set of functions, and does not single out an individual function. For example, if "f" calls itself, that is direct recursion. If instead "f" calls "g" and then "g" calls "f," which in turn calls "g" again, from the point of view of "f" alone, "f" is indirectly recursing, while from the point of view of "g" alone, "g" is indirectly recursing, while from the point of view of both, "f" and "g" are mutually recursing on each other. | wiki:25699875 |
Mutual recursion | Terminology | Similarly a set of three or more functions that call each other can be called a set of mutually recursive functions. | wiki:25699876 |
Mutual recursion | Conversion to direct recursion | Mathematically, a set of mutually recursive functions are primitive recursive, which can be proven by course-of-values recursion, building a single function "F" that lists the values of the individual recursive function in order: formula_1 and rewriting the mutual recursion as a primitive recursion. Any mutual recursion between two procedures can be converted to direct recursion by inlining the code of one procedure into the other. If there is only one site where one procedure calls the other, this is straightforward, though if there are several it can involve code duplication. In terms of the call stack, two mutually recursive procedures yield a stack ABABAB..., and inlining B into A yields the direct recursion (AB)(AB)(AB)... | wiki:25699877 |
Mutual recursion | Conversion to direct recursion | Alternately, any number of procedures can be merged into a single procedure that takes as argument a variant record (or algebraic data type) representing the selection of a procedure and its arguments; the merged procedure then dispatches on its argument to execute the corresponding code and uses direct recursion to call self as appropriate. This can be seen as a limited application of defunctionalization. This translation may be useful when any of the mutually recursive procedures can be called by outside code, so there is no obvious case for inlining one procedure into the other. Such code then needs to be modified so that procedure calls are performed by bundling arguments into a variant record as described; alternately, wrapper procedures may be used for this task. | wiki:25699878 |
Metasyntactic variable | Introduction | A metasyntactic variable is a specific word or set of words identified as a placeholder in computer science and specifically computer programming. These words are commonly found in source code and are intended to be modified or substituted before real-world usage. The words foo and bar are good examples as they are used in over 330 Internet Engineering Task Force Requests for Comments, the documents which define foundational internet technologies like HTTP (websites), TCP/IP, and email protocols. By mathematical analogy, a metasyntactic variable is a word that is a variable for other words, just as in algebra letters are used as variables for numbers. | wiki:25699879 |
Metasyntactic variable | Introduction | Metasyntactic variables are used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept, which is useful for teaching programming. | wiki:25699880 |
Metasyntactic variable | Common metasyntactic variables | Due to English being the foundation-language, or lingua franca, of most computer programming languages these variables are commonly seen even in programs and examples of programs written for other spoken-language audiences. The typical names may depend however on the subculture that has developed around a given programming language. | wiki:25699881 |
Metasyntactic variable | General usage | Metasyntactic variables used commonly across all programming languages include "foobar", "foo", "bar", "baz", "qux", "quux", "quuz", "corge", "grault", "garply", "waldo", "fred", "plugh", "xyzzy", and "thud"; several of these words are references to the game "Colossal Cave Adventure". "Wibble", "wobble", "wubble", and "flob" are also used in the UK. A complete reference can be found in a MIT Press book titled "The Hacker's Dictionary". | wiki:25699882 |
Metasyntactic variable | Japanese | In Japanese, the words "hoge" (ほげ) and "piyo" (ぴよ) are commonly used, with other common words and variants being "fuga" (ふが), "hogera" (ほげら), and "hogehoge" (ほげほげ). Note that "-ra" is a pluralizing ending in Japanese, and reduplication is also used for pluralizing. The origin of "hoge" as a metasyntactic variable is not known, but it is believed to date to the early 1980s. | wiki:25699883 |
Metasyntactic variable | French | In France, the word "toto" is widely used, with variants "tata", "titi", "tutu" as related placeholders. One commonly-raised source for the use of "toto" is a reference to the stock character used to tell jokes with Tête à Toto. | wiki:25699884 |
Metasyntactic variable | C | In the following example the function name foo and the variable name bar are both metasyntactic variables. Lines beginning with // are comments. // The function named foo int foo(void) | wiki:25699885 |
Metasyntactic variable | C++ | Function prototypes with examples of different argument passing mechanisms: void Foo(Fruit bar); void Foo(Fruit* bar); void Foo(const Fruit& bar); Example showing the function overloading capabilities of the C++ language void Foo(int bar); void Foo(int bar, int baz); void Foo(int bar, int baz, int qux); | wiki:25699886 |
Metasyntactic variable | Python | Spam, ham, and eggs are the principal metasyntactic variables used in the Python programming language. This is a reference to the famous comedy sketch, "Spam", by Monty Python, the eponym of the language. In the following example spam, ham, and eggs are metasyntactic variables and lines beginning with # are comments. def spam(): | wiki:25699887 |
Metasyntactic variable | IETF Requests for Comments | Both the IETF RFCs and computer programming languages are rendered in plain text, making it necessary to distinguish metasyntactic variables by a naming convention, since it would not be obvious from context. Here is an example from the official IETF document explaining the e-mail protocols (from RFC 772 - cited in RFC 3092): Another point reflected in the above example is the convention that a metavariable is to be uniformly substituted with the same instance in all its appearances in a given schema. This is in contrast with nonterminal symbols in formal grammars where the nonterminals on the right of a production can be substituted by different instances. | wiki:25699888 |
Metasyntactic variable | SQL | It is common to use the name ACME in example SQL Databases and as placeholder company-name for the purpose of teaching. The term 'ACME Database' is commonly used to mean a training or example-only set of database data used solely for training or testing. ACME is also commonly used in documentation which shows SQL usage examples, a common practice with in many educational texts as well as technical documentation from companies such as Microsoft and Oracle. | wiki:25699889 |
Mondegreen | Introduction | A mondegreen is a mishearing or misinterpretation of a phrase in a way that gives it a new meaning. Mondegreens are most often created by a person listening to a poem or a song; the listener, being unable to clearly hear a lyric, substitutes words that sound similar and make some kind of sense. American writer Sylvia Wright coined the term in 1954, writing that as a girl, when her mother read to her from Percy's "Reliques", she had misheard the lyric "layd him on the green" in the fourth line of the Scottish ballad "The Bonny Earl of Murray" as "Lady Mondegreen". | wiki:25699890 |
Mondegreen | Introduction | "Mondegreen" was included in the 2000 edition of the "Random House Webster's College Dictionary", and in the "Oxford English Dictionary" in 2002. Merriam-Webster's "Collegiate Dictionary" added the word in 2008. | wiki:25699891 |
Mondegreen | Etymology | In a 1954 essay in "Harper's Magazine", Wright described how, as a young girl, she misheard the last line of the first stanza from the seventeenth-century ballad "The Bonnie Earl O' Moray". She wrote: The correct fourth line is, "And "laid him on the green"." Wright explained the need for a new term: | wiki:25699892 |
Mondegreen | Psychology | People are more likely to notice what they expect than things not part of their everyday experiences; this is known as confirmation bias. Similarly, one may mistake an unfamiliar stimulus for a familiar and more plausible version. For example, to consider a well-known mondegreen in the song "Purple Haze", one would be more likely to hear Jimi Hendrix singing that he is about to "kiss this guy" than that he is about to "kiss the sky". Similarly, if a lyric uses words or phrases that the listener is unfamiliar with, they may be misheard as using more familiar terms. The creation of mondegreens may be driven in part by cognitive dissonance, as the listener finds it psychologically uncomfortable to listen to a song and not make out the words. | wiki:25699893 |
Mondegreen | Psychology | Steven Connor suggests that mondegreens are the result of the brain's constant attempts to make sense of the world by making assumptions to fill in the gaps when it cannot clearly determine what it is hearing. Connor sees mondegreens as the "wrenchings of nonsense into sense". This dissonance will be most acute when the lyrics are in a language the listener is fluent in. On the other hand, Steven Pinker has observed that mondegreen mishearings tend to be "less" plausible than the original lyrics, and that once a listener has "locked in" to a particular misheard interpretation of a song's lyrics, it can remain unquestioned, even when that plausibility becomes strained. | wiki:25699894 |
Mondegreen | Psychology | Pinker gives the example of a student "stubbornly" mishearing the chorus to "Venus" ("I'm your Venus") as "I'm your penis," and being surprised that the song was allowed on the radio. The phenomenon may, in some cases, be triggered by people hearing "what they want to hear", as in the case of the song "Louie Louie": parents heard obscenities in the Kingsmen recording where none existed. | wiki:25699895 |
Mondegreen | Notable collections | The classicist and Linguist Steve Reece has collected examples of English mondegreens in song lyrics, religious creeds and liturgies, commercials and advertisements, and jokes and riddles. He has used this collection to shed light on the process of "junctural metanalysis" during the oral transmission of the ancient Greek epics, the "Iliad" and "Odyssey." | wiki:25699896 |
Mondegreen | In songs | The national anthem of the United States is highly susceptible (especially for young grade-school students) to the creation of mondegreens, two in the first line. Francis Scott Key's "Star-Spangled Banner" begins with the line "O say can you see, by the dawn's early light." This has been accidentally and deliberately misinterpreted as "Jose, can you see," another example of the Hobson-Jobson effect, countless times. The second half of the line has been misheard as well, as "by the donzerly light," or other variants. This has led to many people believing that "donzerly" is an actual word. Religious songs, learned by ear (and often by children), are another common source of mondegreens. | wiki:25699897 |
Mondegreen | In songs | The most-cited example is "Gladly, the cross-eyed bear" (from the line in the hymn "Keep Thou My Way" by Fanny Crosby and Theodore E. Perkins, "Kept by Thy tender care, gladly the cross I'll bear"). Jon Carroll and many others quote it as "Gladly the cross "I'd" bear" Mondegreens expanded as a phenomenon with radio, and, especially, the growth of rock and roll (and even more so with rap). Amongst the most-reported examples are: Both Creedence's John Fogerty and Hendrix eventually acknowledged these mishearings by deliberately singing the "mondegreen" versions of their songs in concert. | wiki:25699898 |
Mondegreen | Standardized and recorded mondegreens | Sometimes, the modified version of a lyric becomes standard, as is the case with "The Twelve Days of Christmas". The original has "four colly birds" ("colly" means "black"; cf. "A Midsummer Night's Dream": "Brief as the lightning in the collied night."); by the turn of the twentieth century, these became "calling" birds, which is the lyric used in the 1909 Frederic Austin version. For more on this and other shifts in that song's lyrics, see Variations of the Lyrics. A number of misheard lyrics have been recorded, turning a mondegreen into a real title. The song "Sea Lion Woman", recorded in 1939 by Christine and Katherine Shipp, was performed by Nina Simone under the title, "See Line Woman". | wiki:25699899 |
Mondegreen | Standardized and recorded mondegreens | According to the liner notes from the compilation "A Treasury of Library of Congress Field Recordings", the correct title of this playground song might also be "See [the] Lyin' Woman" or "C-Line Woman". Jack Lawrence's misinterpretation of the French phrase "pauvre Jean" ("poor John") as the identically pronounced "pauvres gens" ("poor people") led to the translation of "La Goualante du pauvre Jean" ("The Ballad of Poor John") as "The Poor People of Paris", a hit song in 1956. | wiki:25699900 |