Investment (military)

Investment is the military process of surrounding an enemy fort (or town) with armed forces to prevent entry or escape. It serves both to cut communications with the outside world, and to prevent supplies and reinforcements from being introduced.

A circumvallation is a line of fortifications, built by the attackers around the besieged fortification facing towards an enemy fort (to protect the besiegers from sorties by its defenders and to enhance the blockade). The resulting fortifications are known as 'lines of circumvallation'. Lines of circumvallation generally consist of earthen ramparts and entrenchments that encircle the besieged city. The line of circumvallation can be used as a base for launching assaults against the besieged city or for constructing further earthworks nearer to the city.

A contravallation may be constructed in cases where the besieging army is threatened by a field army allied to an enemy fort. This is a second line of fortifications outside the circumvallation, facing away from an enemy fort. The contravallation protects the besiegers from attacks by allies of the city's defenders and enhances the blockade of an enemy fort by making it more difficult to smuggle in supplies.

Invest (meteorology)

An invest in meteorology (short for investigative area, alternatively written INVEST) is a designated area of disturbed weather that is being monitored for tropical cyclone development. Invests are designated by three separate forecast centers: the National Hurricane Center, Central Pacific Hurricane Center and Joint Typhoon Warning Center.

Designation

Invests are designated by three separate forecast centers: the National Hurricane Center, Central Pacific Hurricane Center and Joint Typhoon Warning Center. The designation of a system as an invest does not necessarily correspond to any particular likelihood of development of the system into a tropical cyclone. Invests are numbered from 90 to 99, followed by L in the Atlantic, E and C in the East and Central Pacific respectively, or W in the West Pacific; the Joint Typhoon Warning Center also issues unofficial warnings for the Australian cyclone region, designating tropical invests with the "S" suffix when they form west of 135°E, and the "P" suffix when they form east of 135°E. Invests in the North Indian Ocean cyclone basin are also labelled by the JTWC, and are suffixed with "A" if they form in the Arabian Sea and with "B" if they form in the Bay of Bengal. Numbers are rotated within the season and are re-used as necessary (the next invest after 99 would be numbered 90). If the system develops into a tropical cyclone, it is reclassified as the next name/number on the list.

INVEST (mnemonic)

The INVEST mnemonic was created by Bill Wake as a reminder of the characteristics of a good quality user story, as may be used in a Scrum or Kanban backlog or XP project.

Independent

One of the characteristics of Agile Methodologies such as Scrum, Kanban or XP is the ability to move stories around, taking into account their relative priority - for example - without much effort. If you find user stories that are tightly dependent, a good idea might be to combine them into a single user story.

Negotiable

The only thing that is fixed and set in stone in an agile project is an iteration backlog (and, even then, this "can be clarified and re-negotiated... as more is learned."). While the story lies in the product backlog, it can be rewritten or even discarded, depending on business, market, technical or any other type of requirement by team members.

Valuable

The focus here is to bring actual project-related value to the end-user. Coming up with technical stories that are really fun to code but bring no value to the end-user violates one of the Agile Principles, which is to continuously deliver valuable software.

Distributive property

In abstract algebra and formal logic, the distributive property of binary operations generalizes the distributive law from elementary algebra. In propositional logic, distribution refers to two valid rules of replacement. The rules allow one to reformulate conjunctions and disjunctions within logical proofs.

For example, in arithmetic:

In the left-hand side of the first equation, the 2 multiplies the sum of 1 and 3; on the right-hand side, it multiplies the 1 and the 3 individually, with the products added afterwards. Because these give the same final answer (8), it is said that multiplication by 2 distributes over addition of 1 and 3. Since one could have put any real numbers in place of 2, 1, and 3 above, and still have obtained a true equation, we say that multiplication of real numbers distributes over addition of real numbers.

Definition

Given a set S and two binary operators ∗ and + on S, we say that the operation:

∗ is left-distributive over + if, given any elements x, y, and z of S,

Probability distribution

In probability and statistics, a probability distribution assigns a probability to each measurable subset of the possible outcomes of a random experiment, survey, or procedure of statistical inference. Examples are found in experiments whose sample space is non-numerical, where the distribution would be a categorical distribution; experiments whose sample space is encoded by discrete random variables, where the distribution can be specified by a probability mass function; and experiments with sample spaces encoded by continuous random variables, where the distribution can be specified by a probability density function. More complex experiments, such as those involving stochastic processes defined in continuous time, may demand the use of more general probability measures.

In applied probability, a probability distribution can be specified in a number of different ways, often chosen for mathematical convenience:

History monoid

In mathematics and computer science, a history monoid is a way of representing the histories of concurrently running computer processes as a collection of strings, each string representing the individual history of a process. The history monoid provides a set of synchronization primitives (such as locks, mutexes or thread joins) for providing rendezvous points between a set of independently executing processes or threads.

History monoids occur in the theory of concurrent computation, and provide a low-level mathematical foundation for process calculi, such as CSP the language of communicating sequential processes, or CCS, the calculus of communicating systems. History monoids were first presented by M.W. Shields.

History monoids are isomorphic to trace monoids (free partially commutative monoids) and to the monoid of dependency graphs. As such, they are free objects and are universal. The history monoid is a type of semi-abelian categorical product in the category of monoids.