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Burrowing owl

The burrowing owl (Athene cunicularia), also called the shoco, is a small, long-legged owl found throughout open landscapes of North and South America. Burrowing owls can be found in grasslands, rangelands, agricultural areas, deserts, or any other open, dry area with low vegetation. They nest and roost in burrows, such as those excavated by prairie dogs (Cynomys spp.). Unlike most owls, burrowing owls are often active during the day, although they tend to avoid the midday heat. Like many other kinds of owls, though, burrowing owls do most of their hunting during dusk and dawn, when they can use their night vision and hearing to their advantage. Living in open grasslands as opposed to forests, the burrowing owl has developed longer legs that enable it to sprint, as well as fly, when hunting.

Taxonomy
The burrowing owl was formally described by Spanish naturalist Juan Ignacio Molina in 1782 under the binomial name Strix cunicularia from a specimen collected in Chile. The specific epithet is from the Latin cunicularius meaning "burrower" or "miner". The burrowing owl is now placed in the genus Athene that was introduced by German zoologist Friedrich Boie in 1822.

The burrowing owl is sometimes classified in the monotypic genus Speotyto based on an overall different morphology and karyotype. Osteology and DNA sequence data, though, suggest that the burrowing owl is a terrestrial member of the little owls (Athene), and it is today placed in that genus by most authorities.

A considerable number of subspecies have been described, but they differ little in appearance and the taxonomy of several of them needs to be validated. Most subspecies are found in/near the Andes and in the Antilles. Although distinct from each other, the relationship of the Florida subspecies to (and its distinctness from) the Caribbean birds is not quite clear.

The 18 recognised subspecies, of which two are now extinct, are:

includes A. c. partridgei (Olrog, 1976) : Corrientes burrowing owl – Corrientes Province, Argentina, probably not distinct from A. c. cunicularia
 * †A. c. amaura (Lawrence, 1878) : Antiguan burrowing owl – formerly Antigua, Saint Kitts, and Nevis Islands, extinct (circa 1905)
 * A. c. boliviana (L. Kelso, 1939) : Bolivian burrowing owl – the Bolivian altiplano
 * A. c. brachyptera (Richmond, 1896) : Margarita Island burrowing owl – Margarita Island, might include A. c. apurensis
 * A. c. carrikeri (Stone, 1922) : east Colombian burrowing owl – eastern Colombia, doubtfully distinct from A. c. tolimae
 * A. c. cunicularia (Molina, 1782) :- southern burrowing owl – lowlands of southern Bolivia and southern Brazil south to Tierra del Fuego, probably
 *  A. c. floridana (Ridgway, 1874) : Florida burrowing owl – Florida and the Bahamas; listed as Vulnerable
 * A. c. grallaria (Temminck, 1822) : Brazilian burrowing owl – central and eastern Brazil
 * †A. c. guadeloupensis (Ridgway, 1874) : Guadeloupe burrowing owl – formerly Guadeloupe and Marie-Galante Islands, extinct (circa 1890)
 * A. c. guantanamensis (Garrido, 2001) : Cuban burrowing owl – Cuba and Isla de la Juventud
 * A. c. hypugaea (Bonaparte, 1825) : western burrowing owl – southern Canada through the Great Plains south to Central America; listed as Apparently Secure
 * A. c. juninensis (Berlepsch & Stolzmann, 1902) : south Andean burrowing owl – Andes from central Peru to northwestern Argentina, might include A. c. punensis.
 * A. c. minor (Cory, 1918) : Guyanese burrowing owl – southern Guyana and Roraima region
 * A. c. nanodes (Berlepsch & Stolzmann, 1892) : southwest Peruvian burrowing owl – southwestern Peru, might include A. c. intermedia
 * A. c. pichinchae (Boetticher, 1929) : west Ecuadorean burrowing owl – western Ecuador
 * A. c. rostrata (C. H. Townsend, 1890) : Revillagigedo burrowing owl – Clarion Island, Revillagigedo Islands
 * A. c. tolimae (Stone, 1899) : west Colombian burrowing owl – western Colombia, might include A. c. carrikeri
 * A. c. troglodytes (Wetmore & Swales, 1931) : Hispaniolan burrowing owl – Hispaniola (Haiti and the Dominican Republic) and surrounding islands (Gonâve Island, Beata Island)

A paleosubspecies, A. c. providentiae, has been described from fossil remains from the Pleistocene of the Bahamas. How these birds relate to the extant A. c. floridana – that is, whether they were among the ancestors of that subspecies, or whether they represented a more distant lineage that completely disappeared later – is unknown.

In addition, prehistoric fossils of similar owls have been recovered from many islands in the Caribbean (Barbuda, the Cayman Islands, Jamaica, Mona Island and Puerto Rico). These birds became extinct towards the end of the Pleistocene, probably because of ecological and sea-level changes at the end of the last ice age rather than human activity. These fossil owls differed in size from present-day burrowing owls and their relationship to the modern taxon has not been resolved.

Description
Burrowing owls have bright eyes; their beaks can be dark yellow or gray depending on the subspecies. They lack ear tufts and have a flattened facial disc. The owls have prominent white eyebrows and a white "chin" patch which they expand and display during certain behaviors, such as a bobbing of the head when agitated.

Adults have brown heads and wings with white spotting. Their chests and abdomens are white with variable brown spotting or barring, also depending on the subspecies. Juvenile owls are similar in appearance, but they lack most of the white spotting above and brown barring below. The juveniles have a buff bar across their upper wings and their breasts may be buff-colored rather than white. Burrowing owls of all ages have grayish legs longer than those of other owls.

Males and females are similar in size and appearance, so display little sexual dimorphism. Females tend to be heavier, but males tend to have longer linear measurements (wing length, tail length, etc.). Adult males appear lighter in color than females because they spend more time outside the burrow during daylight, and their feathers become "sun-bleached". The burrowing owl measures 19 - 28 cm long and spans 50.8 - 61 cm across the wings, and weighs 140 - 240 g.  As a size comparison, an average adult is slightly larger than an American robin (Turdus migratorius).

Distribution and habitat
Before European colonization, burrowing owls probably inhabited every suitable area of the New World, but in North America, they have experienced some restrictions in distribution since then. In parts of South America, they are expanding their range due to deforestation. The western burrowing owls (A. c. hypugaea) are most common in the Rocky Mountain Arsenal National Wildlife Refuge, as well as in most of the western states. Known resident populations inhabit areas of Colorado, Arizona, New Mexico, Texas and California, where their population is reportedly threatened by human encroachment and construction.

Burrowing owls range from the southern portions of the western Canadian provinces (British Columbia, Alberta, Saskatchewan, Manitoba) and all the way through Mexico to western Panamá. They are also found across the state of Florida, as well as some Caribbean islands. In South America, they are fairly common, and are known to inhabit every country on the continent, with the exception of the dense Amazon rainforest interior and the highest ranges of the Andes Mountains. Their preference is for the cooler, possibly sub-tropical coastal and temperate regions. South of the Amazon, their population seems to again rebound, as they are widely distributed from southern Brazil and the Pantanal down to Patagonia and Tierra del Fuego.

Burrowing owls are year-round residents in most of their range. Birds that breed in Canada and the northern U.S. usually migrate south to Mexico and the southern U.S. during winter months.

Behaviour and ecology

This species can live for at least 9 years in the wild and over 10 years in captivity. They are often killed by vehicles when crossing roads, and have many natural enemies, including badgers, coyotes, and snakes. They are also killed by both feral and domestic cats and dogs. Two birds studied in the Parque Nacional de La Macarena of Colombia were free of blood parasites.

Burrowing owls often nest and roost in the burrows made by ground squirrels, a strategy also used by rattlesnakes. When threatened, the owl retreats to the burrow and produces rattling and hissing sounds similar to those of a rattlesnake. The behavior is suggested to be an example of acoustic Batesian mimicry and has been observed to be an effective strategy against animals that are familiar with the dangers posed by rattlesnakes.

Breeding
The nesting season begins in late March or April in North America. Burrowing owls usually only have one mate but occasionally a male will have two mates. Pairs of owls will sometimes nest in loose colonies. Their typical breeding habitat is open grassland or prairie, but they can occasionally adapt to other open areas like airports, golf courses, and agricultural fields. Burrowing owls are slightly tolerant of human presence, often nesting near roads, farms, homes, and regularly maintained irrigation canals.

The owls nest in a burrow, hence the name burrowing owl. If burrows are unavailable and the soil is not hard or rocky, the owls may excavate their own. Burrowing owls will also nest in shallow, underground, man-made structures that have easy access to the surface.

During the nesting season, burrowing owls will collect a wide variety of materials to line their nest, some of which are left around the entrance to the burrow. The most common material is mammal dung, usually from cattle. At one time it was thought that the dung helped to mask the scent of the juvenile owls, but researchers now believe the dung helps to control the microclimate inside the burrow and to attract insects, which the owls may eat.

The female lays an egg every one or two days until she has completed a clutch, which can consist of four to 12 eggs (usually 9). She then incubates the eggs for 3–4 weeks while the male brings her food. After the eggs hatch, both parents feed the chicks. Four weeks after hatching, the chicks can make short flights and begin leaving the nest burrow. The parents still help feed the chicks for 1–3 months.

Site fidelity rates appear to vary among populations. In some locations, owls will frequently reuse a nest several years in a row. Owls in migratory northern populations are less likely to return to the same burrow every year. Also, as with many other birds, the female owls are more likely to disperse to a different site than are male owls.

Food and feeding
When hunting, they wait on a perch until they spot prey. Then, they swoop down on prey or fly up to catch insects in flight. Sometimes, they chase prey on foot across the ground. The highly variable diet includes invertebrates and small vertebrates, which make up roughly one third and two thirds of the diet, respectively. Burrowing owls mainly eat large insects and small rodents. Although burrowing owls often live close to ground squirrels (Marmotini), they rarely prey upon them. They also hunt bats. An analysis of burrowing owl diets in the Dominican Republic found the owls consumed ~53% invertebrates, ~28% other birds, ~15% reptiles, ~3% amphibians, and 1% mammals.

Rodent prey is usually dominated by locally superabundant species, like the delicate vesper mouse (Calomys tener) in southern Brazil. Among squamates and amphibians, small lizards like the tropical house gecko (Hemidactylus mabouia), snakes, frogs, and toads predominate. Generally, most vertebrate prey is in the weight class of several grams per individual. The largest prey are usually birds, such as eared doves (Zenaida auriculata) which may weigh almost as much as a burrowing owl, as well as sparrows.

Regarding invertebrates, the burrowing owl seems less of a generalist. It is extremely fond of termites such as Termitidae, and Orthoptera such as Conocephalinae and Copiphorinae katydids, Jerusalem crickets (Stenopelmatidae), true crickets (Gryllidae) and grasshoppers. Bothynus and Dichotomius anaglypticus scarab beetles (Scarabaeidae) were eaten far more often than even closely related species by many burrowing owls across central São Paulo (Brazil). Similarly, it was noted that among scorpions Bothriuridae were much preferred, among spiders Lycosidae (wolf spiders), and among millipedes (Diplopoda) certain Diplocheta. Small ground beetles (Carabidae) are eaten in quantity, while larger ones are much less popular as burrowing owl food, perhaps due to the vigorous defense the large species can put up. Earthworms are also preyed upon. Burrowing owls are also known to place the fecal matter of large herbivorous mammals around the outside of their burrows to attract dung beetles, which are used to provide a steady source of food for the owls. Burrowing owls can also predate on invertebrates attracted to artificial night lighting.

Unlike other owls, they also eat fruits and seeds, especially the fruit of tasajillo (Cylindropuntia leptocaulis) and other prickly pear and cholla cacti. On Clarion Island, where mammalian prey is lacking, they feed essentially on crickets and prickly pear fruit, adding Clarión wrens (Troglodytes tanneri) and young Clarion mourning doves (Zenaida macroura clarionensis) on occasion.

Status and conservation
The burrowing owl is endangered in Canada and threatened in Mexico. It is a state threatened species in Colorado and Florida and a California species of special concern. It is common and widespread in open regions of many Neotropical countries, where they sometimes even inhabit fields and parks in cities. In regions bordering the Amazon Rainforest they are spreading with deforestation. It is therefore listed as Least Concern on the IUCN Red List. Burrowing owls are protected under the Migratory Bird Treaty Act in Canada, the United States, and Mexico. They are also included in CITES Appendix II. NatureServe lists the species as Apparently Secure.

California Endangered Species Act Listing Petition
In March 2024, Center for Biological Diversity, Urban Bird Foundation, Defenders of Wildlife, Burrowing Owl Preservation Society, Santa Clara Valley Audubon Society, Central Valley Bird Club and San Bernardino Valley Audubon Society submitted a California Endangered Species Act listing petition to the Fish and Game Commission to get protections for five populations of the western burrowing owl.

The petition requests endangered status for burrowing owls in southwestern California, central-western California and the San Francisco Bay Area, and  threatened status for burrowing owls in the  Central Valley and southern desert  range.

Dependency on burrowing animals
The major reasons for declining populations in North America are loss of habitat, and control programs for prairie dogs. While some species of burrowing owl can dig their own burrows, most species rely on burrowing animals to burrow holes that the owls can use as shelter and nesting space. There is a high correlation between the location of burrowing animal colonies, like those of ground squirrels, with the presence of burrowing owls. Rates of burrowing owl decline have also been shown to correlate with prairie dog decline. Western burrowing owls, for example, nest in burrows made by black-tailed prairie dogs since they are unable to dig their own. However, prairie dog populations have experienced a decline, one of the causes of this being prairie dog eradication programs. When prairie dogs dig burrows, they can uproot plants in the process. This is most common in agricultural areas, where burrows cause damage to existing crops, creating a problem for local farmers. In Nebraska and Montana, eradication programs have already been put in place to manage the population of prairie dogs. Eradication programs for ground squirrels have also been put in place. In California, California ground squirrels have been known to feed on crop seedlings as well as grasses meant for cattle, which prevents crop growth and decreases food supply for cattle. However, as burrowing animal populations decrease, burrowing owls become more vulnerable to exposure to predators. With fewer burrows available, burrowing owl populations will be more concentrated, with more owls occupying fewer burrows. As a result, predators will more easily detect owl populations and be capable of eliminating larger broods of owls at once. Prairie dogs and ground squirrels also act as a buffer between owls and their predators, since they become the target prey rather than the owls. Another benefit prairie dogs in particular provide burrowing owls takes the form of their alarm calls, which alert burrowing owls if predators are nearby, therefore giving the owls ample time to hide or escape. Without burrowing animals, almost every aspect contributing to suitable and safe living for burrowing owls will no longer be available. Organizations have tried contributing to the conservation of burrowing owls by digging artificial burrows for these owls to occupy in areas with no active colony of burrowing animals. However, creating artificial burrows is not sustainable and is not effective as a long term solution.

Anthropogenic impacts
Burrowing owls readily inhabit some anthropogenic landscapes, such as airport grasslands or golf courses, and are known to take advantage of artificial nest sites (plastic burrows with tubing for the entrance) and perches. Burrowing owls have demonstrated similar reproductive success in rural grasslands and urban settings. The urban-residing burrowing owls have also developed the behavior of digging their own burrows and exhibit different fear responses to human and domestic dogs compared to their rural counterparts. Research has suggested that this species has made adaptations to the rapid urbanization of their usual habitat, and conservation efforts should be considered accordingly. Genetic analysis of the two North American subspecies indicates that inbreeding is not a problem within those populations.

Relocation
Where the presence of burrowing owls conflicts with development interests, a passive relocation technique has been applied successfully: rather than capturing the birds and transporting them to a new site (which may be stressful and prone to failure), the owls are half-coerced, half-enticed to move on their own accord. The preparations need to start several months prior to the anticipated disturbance with observing the owl colony and noting especially their local movements and site preferences. After choosing a location nearby that has suitable ground and provides good burrowing owl breeding habitat, this new site is enhanced by adding burrows, perches, etc. Once the owls have accustomed to the changes and are found to be interested in the location – if possible, this should be at the onset of spring, before the breeding season starts – they are prevented from entering the old burrows. A simple one-way trapdoor design has been described that is placed over the burrow for this purpose. If everything has been correctly prepared, the owl colony will move over to the new site in the course of a few nights at most. It will need to be monitored occasionally for the following months or until the major human construction nearby has ended.

Some organizations like Center for Biological Diversity and Urban Bird Foundation contend that the removal from their burrows, either through active or passive relocation, has been a factor in the extirpation of burrowing owl populations in California because of the species high site fidelity.

title: Burrowing owl


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COCOMO

The Constructive Cost Model (COCOMO) is a procedural software cost estimation model developed by Barry W. Boehm. The model parameters are derived from fitting a regression formula using data from historical projects (63 projects for COCOMO 81 and 163 projects for COCOMO II).

History
The constructive cost model was developed by Barry W. Boehm in the late 1970s and published in Boehm's 1981 book Software Engineering Economics as a model for estimating effort, cost, and schedule for software projects. It drew on a study of 63 projects at TRW Aerospace where Boehm was Director of Software Research and Technology. The study examined projects ranging in size from 2,000 to 100,000 lines of code, and programming languages ranging from assembly to PL/I. These projects were based on the waterfall model of software development which was the prevalent software development process in 1981.

References to this model typically call it COCOMO 81. In 1995 COCOMO II was developed and finally published in 2000 in the book Software Cost Estimation with COCOMO II. COCOMO II is the successor of COCOMO 81 and is claimed to be better suited for estimating modern software development projects; providing support for more recent software development processes and was tuned using a larger database of 161 projects. The need for the new model came as software development technology moved from mainframe and overnight batch processing to desktop development, code reusability, and the use of off-the-shelf software components.

COCOMO consists of a hierarchy of three increasingly detailed and accurate forms. The first level, Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs, but its accuracy is limited due to its lack of factors to account for difference in project attributes (Cost Drivers). Intermediate COCOMO takes these Cost Drivers into account and Detailed COCOMO additionally accounts for the influence of individual project phases. Last one is Complete COCOMO model which addresses the shortcomings of both basic & intermediate.

Intermediate COCOMOs
Intermediate COCOMO computes software development effort as function of program size and a set of "cost drivers" that include subjective assessment of product, hardware, personnel and project attributes. This extension considers a set of four "cost drivers", each with a number of subsidiary attributes:-

 * Product attributes
 * Required software reliability extent
 * Size of application database
 * Complexity of the product
 * Hardware attributes
 * Run-time performance constraints
 * Memory constraints
 * Volatility of the virtual machine environment
 * Required turnabout time
 * Personnel attributes
 * Analyst capability
 * Software engineering capability
 * Applications experience
 * Virtual machine experience
 * Programming language experience
 * Project attributes
 * Use of software tools
 * Application of software engineering methods
 * Required development schedule

Each of the 15 attributes receives a rating on a six-point scale that ranges from "very low" to "extra high" (in importance or value). An effort multiplier from the table below applies to the rating. The product of all effort multipliers results in an effort adjustment factor (EAF). Typical values for EAF range from 0.9 to 1.4.

The Intermediate Cocomo formula now takes the form:

where E is the effort applied in person-months, KLoC is the estimated number of thousands of delivered lines of code for the project, and EAF is the factor calculated above. The coefficient ai and the exponent bi are given in the next table.

 * {| class="wikitable"

!Software project !width="20%"|ai !width="20%"|bi !width="20%"|ci ! Organic ! Semi-detached ! Embedded
 * align="center"|3.2
 * align="center"|1.05
 * align="center"|0.38
 * align="center"|3.0
 * align="center"|1.12
 * align="center"|0.35
 * align="center"|2.8
 * align="center"|1.20
 * align="center"|0.32
 * }

The Development time D and also the most effective number of Persons P calculation uses E in the same way as in the Basic COCOMO:

Note that in addition to the EAF, the parameter ai is different in Intermediate COCOMO from the Basic model:

 * {| class="wikitable"

!Software project !width="20%"|ab ! Organic ! Semi-detached ! Embedded
 * align="center"|2.4
 * align="center"|3.0
 * align="center"|3.6
 * }

The parameters b and c are the same in both models.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: COCOMO


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2003 National Assembly for Wales election

The 2003 National Assembly for Wales election was the second general election to the National Assembly for Wales. It was held on 1 May 2003. The election was characterised by a resurgence for the Labour Party, whilst Plaid Cymru saw a reduction in support and the number of Assembly Members they returned. Having won thirty seats, one short of a majority, Labour chose to govern in minority without a coalition partner.

This election also saw the returning of John Marek as an independent member of the Assembly. Of the 60 members elected, 30 were male and 30 were female.

It was held on the same day as the 2003 Scottish Parliament election and 2003 United Kingdom local elections.

Party leaders in 2003

 * Welsh Labour - Rhodri Morgan
 * Plaid Cymru - Ieuan Wyn Jones
 * Welsh Conservatives - Nicholas Bourne
 * Welsh Liberal Democrats - Michael James German
 * UK Independence Party (UKIP) - Roger Knapman

National vote

 * Overall turnout - 38.2%

!rowspan=3 colspan=2 | Parties !colspan=10 | Additional member system !rowspan=2 colspan=5 | Total seats !colspan=5 |Constituency !colspan=5 |Region ! Votes !! % !! +/− !! Seats !! +/− ! Votes !! % !! +/− !! Seats !! +/− ! Total !! +/− !! %
 * style="background-color:white" colspan=15 | Welsh assembly election 2003.svg
 * style="background-color:white" colspan=15 | Welsh assembly election 2003.svg

 * || Total || 851,357 || ||  || 40 ||   || 849,552 ||  ||   || 20 ||  || 60 ||   ||
 * }
 * }

Mid and West Wales
! colspan=2 |Constituency ! Elected member ! Result

North Wales
! colspan=2 |Constituency ! Elected member ! Result

South Wales Central
! colspan=2 |Constituency ! Elected member ! Result

South Wales East
! colspan=2 |Constituency ! Elected member ! Result

South Wales West
! colspan=2 |Constituency ! Elected member ! Result


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Liverpool City Council

Liverpool City Council is the local authority for the city of Liverpool in Merseyside, England. Liverpool has had a local authority since 1207, which has been reformed on numerous occasions. Since 1974 the council has been a metropolitan borough council. It provides the majority of local government services in the city. The council has been a member of the Liverpool City Region Combined Authority since 2014.

The council has been under Labour majority control since 2010. It meets at Liverpool Town Hall and has its main offices at the Cunard Building.

History
Liverpool was an ancient borough, having been granted its first charter by King John in 1207. It had a mayor from at least 1292.

Municipal borough
Liverpool was reformed to become a municipal borough in 1836 under the Municipal Corporations Act 1835, which standardised how most boroughs operated across the country. It was then governed by a body formally called the 'mayor, aldermen and burgesses of the borough of Liverpool', generally known as the corporation or town council. As part of the same reforms, the borough boundaries were enlarged to match the larger Liverpool parliamentary constituency, which had been expanded in 1832 to include the neighbouring parishes of Everton and Kirkdale and part of West Derby. The corporation created a police force in 1836.

Liverpool was granted city status in 1880, after which the corporation was also known as the city council. When elected county councils were established in 1889, Liverpool was considered large enough to provide its own county-level services, and so it became a county borough, independent from the new Lancashire County Council, whilst remaining part of the geographical county of Lancashire. In 1893 the city was granted the right to appoint a lord mayor.

The city boundaries were enlarged on several occasions, notably gaining Wavertree, Walton and parts of Toxteth and West Derby in 1895, Fazakerley in 1905, Allerton, Childwall and Woolton in 1913, the rest of West Derby in 1928, and Speke in 1932.

Liverpool's first female councillor was Eleanor Rathbone, elected in 1909. Eighteen years later, Margaret Beavan became the first female Lord Mayor in 1927.

Metropolitan borough
The city was reformed to become a metropolitan district in 1974 under the Local Government Act 1972. It kept the same boundaries as the former county borough (which had last been adjusted in 1956) and became one of five metropolitan districts within the new metropolitan county of Merseyside. Liverpool's borough and city statuses and its lord mayoralty passed to the reformed district and its council.

From 1974 until 1986 the council was a lower-tier authority, with upper-tier functions provided by Merseyside County Council. The county council was abolished in 1986 and its functions passed to Merseyside's five borough councils, including Liverpool, with some services provided through joint committees.

During the 1980s, the Militant group gained control of Liverpool's Labour Party. Under their leadership the council attempted to challenge the national government on several issues, including refusing to set a budget in 1985. The leadership of the national Labour Party was drawn into the controversy, ultimately expelling members of Militant, including the council's deputy leader, Derek Hatton, in 1986.

In 2012 the council introduced the position of Mayor of Liverpool as a directly elected mayor to serve as the council's political leader instead of having a leader of the council chosen by the councillors. The position was separate from the more ceremonial role of the Lord Mayor. The directly elected mayor position was abolished in 2023 and the position of leader of the council was reinstated.

Since 2014 the council has been a member of the Liverpool City Region Combined Authority, which has been led by the directly elected Mayor of the Liverpool City Region since 2017. The combined authority provides strategic leadership and co-ordination for certain functions across the region, but Liverpool City Council continues to be responsible for most local government functions.

The council's chief executive, Ged Fitzgerald, was suspended in 2017 and subsequently resigned in 2018 following an investigation by Lancashire Constabulary into financial irregularities relating to a joint project between Lancashire County Council and British Telecom (BT) during Fitzgerald's tenure as chief executive of the county council. The police investigation subsequently widened to investigate alleged criminality at the city council and the Merseyside pension fund too. In 2020, it was reported that the city council's accounts since 2015 had not been signed off by its auditors on account of the 'complex ongoing police investigation'.

In December 2020, the elected mayor, Joe Anderson, was arrested as part of an anti-corruption investigation. The Labour Party suspended Anderson on news of his arrest. He did not resign as mayor but stood back from active duties, handing effective control to the deputy mayor, Wendy Simon, for the remainder of his term of office to May 2021. As of April 2024 no charges had been brought against him, but the investigation had yet to conclude.

On 24 March 2021, the Secretary of State for Housing, Communities and Local Government, Robert Jenrick, announced that he was appointing commissioners to oversee some of the authority's functions for at least 3 years. This was following an investigation, commissioned in December 2020 that found there were "multiple apparent failures" and a "deeply concerning picture of mismanagement" in the council.

The commissioners remained in post until June 2024. Following improvements in the council's performance and management, the intervention was then scaled back to less direct supervision, due to last until March 2025.

Governance
Liverpool City Council provides metropolitan borough services. Some strategic functions in the area are provided by the Liverpool City Region Combined Authority; the leader of Liverpool City Council sits on the combined authority as Liverpool's representative. There are no civil parishes in the city.

Political control
The council has been under Labour majority control since 2010.

In the late nineteenth and early twentieth centuries, the council was run by the Conservatives. Labour councillors were first elected to the council in 1905, but Liverpool was one of the last major cities in the UK in which the Labour Party gained control, which first occurred in 1955.

Municipal borough

Political control of the council since the 1974 reforms has been as follows:

Metropolitan borough

Leadership
The role of Lord Mayor of Liverpool is largely ceremonial role. Political leadership is instead provided by the leader of the council. Between 2012 and 2023 the council had a directly elected Mayor of Liverpool (a separate post from the Lord Mayor) instead of a leader. The directly elected mayor position was abolished in 2023 and the position of leader reinstated. The leaders since 1918 have been:

County Borough leaders The last leader of the council before the 1974 reforms, Bill Sefton, went on to be the first leader of Merseyside County Council.

Metropolitan Borough leaders

Directly elected mayors

Metropolitan Borough leaders

Composition
Following the 2023 election the composition of the council was:

The next election is due in 2027.

Elections
Since the last boundary changes in 2023, 85 councillors have been elected from 64 wards, with each ward electing one, two or three councillors. Elections are held every four years.

These are the wards since the 2023 local elections.

Premises
Council meetings are held at Liverpool Town Hall at the junction of High Street, Dale Street and Water Street, which was built between 1749 and 1754. The council's main administrative offices are located in the Cunard Building at Pier Head, which had been completed in 1917 as the headquarters of the Cunard Line. The council bought the building in 2013.

From 1868 until 2016 the council's main offices were the Municipal Buildings on Dale Street. The Municipal Buildings were sold in 2016 after the council decided they were too large and costly to maintain and following the transfer of most offices to the Cunard Building.

title: Liverpool City Council


text:
Log-structured file system

A log-structured filesystem is a file system in which data and metadata are written sequentially to a circular buffer, called a log. The design was first proposed in 1988 by John K. Ousterhout and Fred Douglis and first implemented in 1992 by Ousterhout and Mendel Rosenblum for the Unix-like Sprite distributed operating system.

Rationale
Conventional file systems tend to lay out files with great care for spatial locality and make in-place changes to their data structures in order to perform well on optical and magnetic disks, which tend to seek relatively slowly.

The design of log-structured file systems is based on the hypothesis that this will no longer be effective because ever-increasing memory sizes on modern computers would lead to I/O becoming write-heavy because reads would be almost always satisfied from memory cache. A log-structured file system thus treats its storage as a circular log and writes sequentially to the head of the log.

This has several important side effects:
 * Write throughput on optical and magnetic disks is improved because they can be batched into large sequential runs and costly seeks are kept to a minimum.
 * The structure is naturally suited to media with append-only zones or pages such as flash storages and shingled magnetic recording HDDs
 * Writes create multiple, chronologically-advancing versions of both file data and meta-data. Some implementations make these old file versions nameable and accessible, a feature sometimes called time-travel or snapshotting. This is very similar to a versioning file system.
 * Recovery from crashes is simpler. Upon its next mount, the file system does not need to walk all its data structures to fix any inconsistencies, but can reconstruct its state from the last consistent point in the log.

Log-structured file systems, however, must reclaim free space from the tail of the log to prevent the file system from becoming full when the head of the log wraps around to meet it. The tail can release space and move forward by skipping over data for which newer versions exist farther ahead in the log. If there are no newer versions, then the data is moved and appended to the head.

To reduce the overhead incurred by this garbage collection, most implementations avoid purely circular logs and divide up their storage into segments. The head of the log simply advances into non-adjacent segments which are already free. If space is needed, the least-full segments are reclaimed first. This decreases the I/O load (and decreases the write amplification) of the garbage collector, but becomes increasingly ineffective as the file system fills up and nears capacity.

Disadvantages
The design rationale for log-structured file systems assumes that most reads will be optimized away by ever-enlarging memory caches. This assumption does not always hold:
 * On magnetic media—where seeks are relatively expensive—the log structure may actually make reads much slower, since it fragments files that conventional file systems normally keep contiguous with in-place writes.
 * On flash memory—where seek times are usually negligible—the log structure may not confer a worthwhile performance gain because write fragmentation has much less of an impact on write throughput. Another issue is stacking one log on top of another log, which is not a very good idea as it forces multiple erases with unaligned access. However many flash based devices cannot rewrite part of a block, and they must first perform a (slow) erase cycle of each block before being able to re-write, so by putting all the writes in one block, this can help performance as opposed to writes scattered into various blocks, each one of which must be copied into a buffer, erased, and written back, which is a clear advantage for so-called "raw" flash memory where flash translation layer is bypassed.

title: Log-structured file system


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Verse paragraph

Verse paragraphs are stanzas with no regular number of lines or groups of lines that make up units of sense. They are usually separated by blank lines. It stands for a group of lines in a poem that form a rhetorical unit similar to that of a prose paragraph.

Milton's Paradise Lost and Wordsworth's The Prelude consist of verse paragraphs.

Verse paragraphs are frequently used in blank verse and in free verse.

title: Verse paragraph


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Otto Grotewohl

Otto Emil Franz Grotewohl (11 March 1894 – 21 September 1964) was a German politician who served as the first prime minister of the German Democratic Republic (GDR/East Germany) from its foundation in October 1949 until his death in September 1964.

Grotewohl was a Social Democratic Party (SPD) politician in the Free State of Brunswick during the Weimar Republic and leader of the party branch in the Soviet Occupation Zone after World War II. Grotewohl led the SPD's merger with the Communist Party (KPD) to form the Socialist Unity Party of Germany (SED) in 1946 and served as co-chairman of the party with KPD leader Wilhelm Pieck until 1950. Grotewohl chaired the Council of Ministers after the establishment of the GDR in 1949 and served as the de jure head of government under First Secretary Walter Ulbricht until his death in 1964.

Early years
Grotewohl was born on 11 March 1894 in Braunschweig to a middle-class Protestant family, the son of a master tailor, and was apprenticed to a printer. At the age of 16 he joined the youth wing of the Social Democratic Party of Germany. Grotewohl served in the German Army during World War I, and started his political career after the war as a leader of the Independent Social Democratic Party of Germany (USPD), and in 1920 was elected to the Landtag of the Free State of Brunswick in the Weimar Republic. Grotewohl served as a minister in numerous cabinets of the Brunswick state government, including Minister of Justice and Education from March to May 1922, and Minister of Justice from February 1923.

In 1922, Grotewohl and the majority of the USPD members joined the Social Democratic Party, and on 31 October 1925 he became a member of parliament in the national Reichstag to replace the SPD representative Elise Bartels after her death. Grotewohl was elected to the Reichstag in his own right in the September 1930 election and re-elected in the July 1932, November 1932, and March 1933 elections.

Nazi era
Grotewohl was eventually dismissed as a representative in the Reichstag after the Machtergreifung, the establishment of Nazi Germany, and like other SPD members was subject to discrimination. On 23 March 1933, Grotewohl had voted against Chancellor Adolf Hitler's Enabling Act, a constitutional amendment allowing Hitler to enact laws without the Reichstag's approval, which passed. Grotewohl was brutally beaten, arrested and imprisoned several times by Nazi police and subsequently forced to leave Braunschweig, first moving to Hamburg then from 1938 to Berlin, where he worked as a greengrocer and industrial representative. Grotewohl joined a resistance group centered around Erich Gniffke, an SPD politician he knew from Braunschweig, but the group ended up ensuring the contact and economic survival of its members rather than resisting Nazi rule. In August 1938, Grotewohl was again brutally beaten, arrested and charged by Nazi police with treason before the People's Court. On 4 March 1939, Grotewohl was released from pre-trial detention and the court's procedure against him was discontinued after seven months. Grotewohl was again brutally beaten and arrested by Nazi police after Georg Elser's attempted assassination of Adolf Hitler and other high-ranking Nazis on 8 November 1939, spending about eight weeks in custody before being released. Grotewohl worked as a clerk in Berlin after his release and increasingly devoted his time to painting. Grotewohl had been scheduled for arrest again on 20 July 1944, but the Gestapo was unable to locate him because he was now living off-the-grid. According to Heinz Voßke's 1979 biography of Grotewohl, this lifestyle allowed him to avoid being conscripted into the Volkssturm during the closing months of World War II.

Formation of the Socialist Unity Party
After German defeat in World War II in May 1945, the country was occupied by the Allied forces and divided into four zones governed by the United States, the Soviet Union, the United Kingdom, and France, respectively. Grotewohl and several other former SPD politicians founded a branch of the re-established Social Democratic Party of Germany in the Soviet Occupation Zone, and he became the branch leader as Chairman of the Central Committee. Immediately after the war, the Soviets believed the Communist Party of Germany (KPD), rebuilt by the "Ulbricht Group" and led by Wilhelm Pieck, would naturally develop into the strongest political force in their zone with some guidance. However, Soviet leader Joseph Stalin and KPD deputy leader Walter Ulbricht began to push for a merger with the eastern SPD after the poor performance of communist parties in elections in Hungary and Austria in November 1945. The SPD in the Soviet zone faced increasing pressure from the Soviet Military Administration (SVAG) to merge with the KPD, despite historic animosity between the two parties. Unification was pushed by some members of Grotewohl's SPD in the Soviet zone and Berlin, under the belief that division between the main left-wing parties had led to Nazi rise to power. Grotewohl initially opposed the merger, but under duress from Ulbricht and SVAG soon yielded and became a proponent of a quick unification. Grotewohl's change of heart was fiercely opposed by Kurt Schumacher, a prominent member of the eastern SPD and anti-communist, who subsequently became leader of the western SPD after the merger.

In April 1946, the KPD and the eastern branch of the SPD merged as the Socialist Unity Party (SED), with Pieck and Grotewohl serving as co-chairmen. Grotewohl's hand appeared alongside Pieck's on the SED's "handshake" logo derived from the SPD-KPD congress establishing the party where he symbolically shook hands with Pieck. Grotewohl's position allowed him to avoid the systematic sidelining and exclusion of former SPD members that began soon after the merger. The few recalcitrant SPD supporters were condemned as "Agents of Schumacher" and shunted aside, accelerating a process that left the SED as essentially the KPD under a new name. Eventually, Grotewohl was one of the few holdovers from the SPD half of the merger to have a prominent post in the merged party.

In 1948, Grotewohl became Chairman of the constitutional committee of the German People's Council, the predecessor of the Volkskammer.

Prime Minister

On 12 October 1949, Grotewohl became the first prime minister (Ministerpräsident) of the German Democratic Republic (commonly known as East Germany or the GDR), five days after its establishment from the Soviet Occupation Zone with the SED as the ruling party. Grotewohl was appointed Chairman of the Council of Ministers (Ministerrat), the de jure government of the GDR, while Pieck served as State President. Although Grotewohl and Pieck were officially on equal footing, Grotewohl wielded far more real political power in state affairs than Pieck. In the East German political hierarchy, the prime minister was the highest state official, with the president nominally ranking second. Thus, for the GDR's first year of existence, Grotewohl was the most powerful politician in the country.

Grotewohl's power was significantly reduced in July 1950, when the SED restructured along more orthodox Soviet lines. Ulbricht became First Secretary of the SED's Central Committee, the de facto power center of the GDR, and thus the de facto leader of East Germany. Grotewohl remained as Chairman of the Council of Ministers and the official head of government without challenge from the SED. However, the Council of Ministers, despite being officially defined as the "government" of East Germany, was reduced to a transmission belt for policies made by the SED's Politburo. Grotewohl was this left as mostly a figurehead without any real influence on state affairs. Grotewohl was a member of the delegation that signed the Treaty of Zgorzelec on the recognition of the Oder-Neisse border as a border between the GDR and the People's Republic of Poland. In 1957, Grotewohl advocated for the Rapacki Plan for a nuclear weapon-free zone in Central Europe.

Unlike Ulbricht and most of his other SED colleagues, Grotewohl was known to openly favour a more humane way of governing. He condemned abuses in the legal system in a major speech at the SED party conference on 28 March 1956. He also denounced illegal arrests, called for more respect for civil rights, and even called for lively debate in the Volkskammer. Grotewohl also made a veiled criticism of Justice Minister Hilde Benjamin's notoriously high-handed handling of political trials. Despite his open criticism of the SED's increasingly heavy-handed rule, Grotewohl retained his posts without reprisal because the Kremlin maintained its trust in him.

Last years and death
Grotewohl, who was 55 years old upon coming to power, faced rapidly declining health during his premiership. Grotewohl was repeatedly taken to a government hospital during the 1950s, typically minor examinations in which he was released on the same day, but also multi-day stays. However, Grotewohl was not only examined by specialist physicians in the GDR, who identified arteriosclerosis and incipient calcification of the coronary system in his heart in 1953, but also took advantage of the medical care of top Soviet politicians in Moscow. On 12 November 1953, Grotewohl visited the Kremlin Polyclinic in Moscow. Afterwards, Grotewohl completed a three-and-a-half-week cure on the Black Sea. He reportedly took advantage of these unofficial stays in Moscow to conduct political talks with the Kremlin, but there are no official records. From 1955, Grotewohl's doctors were worried about the condition of his cardiovascular system. In 1959, they finally diagnosed incipient heart failure and pushed for a reduction in workload. Due to the persistent high blood pressure and the chronic arrhythmia, the physicians feared a heart attack.

In 1960, Grotewohl was diagnosed with leukemia, and the course of the year saw his health deteriorate rapidly to the point he was barely able to participate in daily political business. On 4 April 1960, Grotewohl traveled to a four-week relaxing holiday on the Black Sea; eight months later, he arrived again for several weeks in the Soviet sanatorium in Barwicha. After his return from the Soviet Union, he reluctantly moved with his wife from Pankow to Wandlitz, giving in to a previous decision from Ulbricht. At the end of October 1960, Grotewohl had commissioned his top deputy, Willi Stoph, as acting prime minister, although he officially remained in office. The permanent cardiovascular disorders prevented Grotewohl's return to politics, and he was no longer able to participate actively in the meetings of the leadership committees of the party and the government. As his eyesight also faded, he could no longer read any script, which is why there are hardly any public speeches from him at the beginning of 1961. Despite the clear medical situation, his resignation was out of the question. On the contrary, in September 1960 Grotewohl became Deputy Chairman of the State Council, the collective body that was created on the base of the Presidency which was abolished after Wilhelm Pieck's death in 1960.

Grotewohl died on 21 September 1964, at 12:35 noon, in the Niederschönhausen area of Pankow, East Berlin, from the complications of a brain haemorrhage. A few hours later, the GDR flag on the Brandenburg Gate was lowered half-mast and the Deutscher Fernsehfunk broadcasting was interrupted. The GDR Council of Ministers ordered 3-day mourning period and Grotewohl was lying in state in the SED Headquarters. On 15 October, his ashes were buried at the Memorial to the Socialists (Gedenkstätte der Sozialisten) in the Friedrichsfelde Central Cemetery, Berlin.

Legacy
After his death, the Wilhelmstrasse in East Berlin was renamed Otto-Grotewohl-Straße in his honor; the street retained this name until 1991, following German reunification. On 15 April 1986, the present-day Mohrenstraße U-Bahn station in eastern Berlin, then known as the Thälmannplatz station, was also renamed Otto-Grotewohl-Straße. The Third German School in Chapayesky Lane, Moscow, was named the Otto Grotewohl School.

Personal life
Grotewohl was married to Marie Martha Louise (née Ohst) from 1919 until 1949. The couple had two children, a son Hans and daughter Dorle. Hans Grotewohl (1924–1999), was an architect who was sent by his father to lead a German Work Team for rebuilding Hamhung, North Korea, in 1954 after the Korean War. Grotewohl married his secretary, Johanna Schumann (née Danielzik) the same year as his divorce from Ohst.

He was an avid painter and amateur filmmaker.

title: Otto Grotewohl


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Rhyme scheme

A rhyme scheme is the pattern of rhymes at the end of each line of a poem or song. It is usually referred to by using letters to indicate which lines rhyme; lines designated with the same letter all rhyme with each other.

An example of the ABAB rhyming scheme, from "To Anthea, who may Command him Anything", by Robert Herrick:

Function in writing
These rhyme patterns have various effects, and can be used to:

 * Control flow: If every line has the same rhyme (AAAA), the stanza will read as having a very quick flow, whereas a rhyme scheme like ABCABC can be felt to unfold more slowly.
 * Structure a poem's message and thought patterns: For example, a simple couplet with a rhyme scheme of AABB lends itself to simpler direct ideas, because the resolution comes in the very next line. Essentially these couplets can be thought of as self-contained statements. This idea of rhyme schemes reflecting thought processes is often discussed particularly regarding sonnets.
 * Determine whether a stanza is balanced or unbalanced.
 * Help to reinforce the feeling being expressed: If the writer wants to express stubbornness, they may use tight structured rhyme schemes, whereas if one was writing about feeling lost, then perhaps the stanza would only have one rhyme (XXAXXXA).

A basic distinction is between rhyme schemes that apply to a single stanza, and those that continue their pattern throughout an entire poem (see chain rhyme). There are also more elaborate related forms, like the sestina – which requires repetition of exact words in a complex pattern. Rhyming is not a mandatory feature of poetry; a four-line stanza with non-rhyming lines could be described as using the scheme ABCD.

Notation and examples
Notation used below:
 * ABAB – Four-line stanza, first and third lines rhyme at the end, second and fourth lines rhyme at the end.
 * AB AB – Two two-line stanzas, with the first lines rhyming at the end and the second lines rhyming at the end.
 * AB,AB – Single two-line stanza, with the two lines having both a single internal rhyme and a conventional rhyme at the end.
 * aBaB – Two different possible meanings for a four-line stanza:
 * First and third lines rhyme at the end, second and fourth lines are repeated verbatim.
 * First and third lines have a feminine rhyme and the second and fourth lines have a masculine rhyme.
 * A1abA2 A1abA2 – Two stanzas, where the first lines of both stanzas are exactly the same, and the last lines of both stanzas are the same. The second lines of the two stanzas are different, but rhyme at the end with the first and last lines.  (In other words, all the "A" and "a" lines rhyme with each other, but not with the "b" lines.)
 * XAXA – Four lines, two unrhymed (X) and two with the same end rhyme (A)

Other notation examples:
 * Indicating the number of stressed syllables in certain lines: AA4B2CC4 or AA4B2CC4
 * Some publications use lowercase or have punctuation to separate lines or stanzas, e.g. abba cdcd or a-b-b-a,c-d-c-d. (These variations are not used elsewhere in this article, for clarity.)

Notable rhyme schemes and forms that use specific rhyme schemes:
 * Ballad stanza: ABCB
 * Ballade: Three stanzas of ABABBCBC followed by BCBC
 * Balliol rhyme: AABB
 * Boy Named Sue: AABCC(B, or infrequently D)
 * Bref double: AXBC XAXC AXAB AB and other schemes, where "X" represents unrhymed lines
 * Burns stanza: AAABAB(B) or AABCCCB
 * Canopus: ABABCBC
 * Chant royal: Five stanzas of ababccddedE followed by either ddedE or ccddedE (capital letters represent lines repeated verbatim)
 * Chastushka: ABAB, ABCB, or AABB
 * Cinquain: ABABB
 * Clerihew: AABB
 * Couplet: AA, but usually occurs as AA BB CC DD ...
 * Décima: ABBAACCDDC
 * Double dactyl: XXXA XXXA
 * Enclosed rhyme (or enclosing rhyme): ABBA
 * Englyn: complex structure
 * "Fire and Ice" stanza: ABAABCBCB as used in Robert Frost's poem "Fire and Ice"
 * Keatsian Ode: ABABCDECDE used in Keats' Ode on Indolence, Ode on a Grecian Urn, and Ode to a Nightingale.
 * Klin: complex structure
 * Limerick: AABBA
 * Lutherstrophe: ABABCCB or ABABCCX
 * Mâni: AABA
 * Monorhyme: AAAAA... an identical rhyme on every line, common in Latin and Arabic
 * Octave: ABBA ABBA
 * Onegin stanzas: aBaBccDDeFFeGG with the lowercase letters representing feminine rhymes and the uppercase representing masculine rhymes, written in iambic tetrameter
 * Ottava rima: ABABABCC
 * A quatrain is any four-line stanza or poem. There are 15 possible rhyme sequences for a four-line poem; common rhyme schemes for these include AAAA, AABB, ABAB, ABBA, and ABCB.
 * "The Raven" stanza: ABCBBB, or AA,B,CC,CB,B,B when accounting for internal rhyme, as used by Edgar Allan Poe in his poem "The Raven"
 * Rhyme royal: ABABBCC
 * The Road Not Taken stanza: ABAAB as used in Robert Frost's poem The Road Not Taken, and in Glæde over Danmark by Poul Martin Møller.
 * Rondeau: ABaAabAB (capital letters represent lines repeated verbatim)
 * Rondelet: AbAabbA (capital letters represent lines repeated verbatim)
 * Roundel: abaB bab abaB (capital letters represent lines repeated verbatim)
 * Rubaiyat: AABA or AAAA
 * Sapphic stanza in Polish poetry - various
 * Scottish stanza: AAABAB, as used by Robert Burns in works such as "To a Mouse"
 * Sestain: AABBCC, ABABCC, AABCCB, AAABAB, and others
 * Sestet: various schemes depending on the country
 * Sestina: ABCDEF FAEBDC CFDABE ECBFAD DEACFB BDFECA, the seventh stanza is a tercet where line 1 has A in it but ends with D, line 2 has B in it but ends with E, line 3 has C in it but ends with F
 * Sestuplo-nel-quintetto: Any quantity of stanzas of AABCCB, occasionally followed by either a repeating pattern of BCCB, or AA, plainly.
 * Sicilian octave: ABABABAB
 * Simple 4-line: ABCB
 * Sonnet, 14 lines:
 * 4 + 4 + 3 + 3 lines:
 * Petrarchan sonnet: ABBA ABBA CDE CDE or ABBA ABBA CDC DCD
 * 4 + 4 + 4 + 2 lines
 * Shakespearean sonnet: ABAB CDCD EFEF GG
 * Spenserian sonnet: ABAB BCBC CDCD EE
 * Spenserian stanza: ABABBCBCC, where the last line is an alexandrine line
 * Stopping by Woods on a Snowy Evening form: AABA BBCB CCDC DDDD, a modified Ruba'i stanza used by Robert Frost for the eponymous poem
 * Tail rhyme: B lines appear intermittently
 * Tanaga: traditional Tagalog tanaga is AABB
 * Terza rima: ABA BCB CDC ..., ending on YZY Z; YZY ZZ; or YZY ZYZ
 * A tristich or tercet is any three-line stanza or poem; common rhyme schemes for these are AAA (triplet) and ABA (enclosed tercet). The only other possibilities for three-line poems are AAB, ABB, and ABC.  Multiple tercets can be combined into longer poems, as in the terza rima form.
 * Traditional rhyme: ABAB CDCD EFEF GHGH...
 * Triolet: ABaAabAB and others (capital letters represent lines repeated verbatim)
 * Triplet: AAA, often repeating such as: AAA BBB CCC DDD...
 * Trova: XAXA
 * Villanelle: A1bA2 abA1 abA2 abA1 abA2 abA1A2, where A1 and A2 are lines repeated exactly which rhyme with the "a" lines

In hip-hop music
Hip-hop music and rapping's rhyme schemes include traditional schemes such as couplets, as well as forms specific to the genre, which are broken down extensively in the books How to Rap and Book of Rhymes. Rhyme schemes used in hip-hop music include
 * Couplets
 * Single-liners
 * Multi-liners
 * Combinations of schemes
 * Whole verse

Couplets are the most common type of rhyme scheme in old school rap and are still regularly used, though complex rhyme schemes have progressively become more frequent. Rather than relying on end rhymes, rap rhyme schemes can have rhymes placed anywhere in the bars of music to create a structure. There can also be numerous rhythmic elements which all work together in the same scheme – this is called internal rhyme in traditional poetry, though rap rhymes schemes can be anywhere in the bar, they could all be internal, so the term is not always used. Rap verses can also employ 'extra rhymes', which do not structure the verse like the main rhyme schemes, but which add to the overall sound of the verse.

Number of rhyme schemes for a poem with n lines
The number of different possible rhyme schemes for an n-line poem is given by the Bell numbers, which for n = 1, 2, 3, ... are
 * 1, 2, 5, 15, 52, 203, 877, 4140, 21147, 115975, ...

Examples: We find one rhyme scheme for a one-line poem (A), two different rhyme schemes for a two-line poem (AA, AB), and five for a three-line poem: AAA, AAB, ABA, ABB, and ABC.

These counts, however, include rhyme schemes in which rhyme is not employed at all (ABCD). There are many fewer rhyme schemes when all lines must rhyme with at least one other line; a count of these is given by the numbers,
 * 0, 1, 1, 4, 11, 41, 162, 715, 3425, 17722, ....

For example, for a three-line poem, there is only one rhyming scheme in which every line rhymes with at least one other (AAA), while for a four-line poem, there are four such schemes (AABB, ABAB, ABBA, and AAAA).

title: Rhyme scheme