https://RustRocket.rs -- Cloud Monk Losang Jinpa, Ph.D., MCSE / MCT, https://Rustaceans.rs, Full Stack Cloud Native Rust DevOps Engineer - Rocket Framework Rust Microservices on Kubernetes-AWS-Azure-GCP

, a

that a predicate (Boolean-valued function, i.e. a true–false

) is always true at that point in code execution. It can help a programmer read the code, help a

compile it, or help the program detect its own defects. For the latter, some programs check assertions by actually evaluating the predicate as they run and if it is not in fact true – an assertion failure – the program considers itself to be broken and typically deliberately

or throws an assertion failure exception.}}

</ref><ref name=“ms”>

</ref>

• the addition of a pair to the collection
• the removal of a pair from the collection
• the modification of an existing pair
• the lookup of a value associated with a particular key}}

and discrete mathematics (a subject of study in both mathematics and

).}}

and mathematical logic dedicated to understanding different aspects of reasoning. The study of automated reasoning helps produce computer programs that allow computers to reason completely, or nearly completely, automatically. Although automated reasoning is considered a sub-field of

, it also has connections with

, and even philosophy.}}

, a set of programs, or other operations, in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it.<ref>

to adequately deal with. Data with many cases (rows) offer greater statistical power, while data with higher complexity (more attributes or columns) may lead to a higher false discovery rate.<ref>

</ref>}}

</ref> Edmund Landau,<ref name=Landau>

</ref> logarithmic search,

or binary chop.

}}

that finds the position of a target value within a sorted array.<ref>

</ref><ref>

</ref>}}

</ref> Some authors allow the binary tree to be the empty set as well.<ref name=“Skiena2009”>

</ref>}}

digit can have one of two possible

, and may be physically represented with a two-state device. These state values are most commonly represented as either a

.<ref name=“Mackenzie_1980”>

s://web.archive.org/web/20160526172151/https://textfiles.meulie.net/bitsaved/Books/Mackenzie_CodedCharSets.pdf</ref>}}

, the number of

that are conveyed or processed per unit of time.<ref>

</ref>}}

, a basic access control mechanism that allows through all elements (email addresses, users, passwords, URLs, IP addresses, domain names, file hashes, etc.), except those explicitly mentioned in a list of prohibited elements. Those items on the list are denied access. The opposite is a

, which means only items on the list are allowed through whatever gate is being used while all other elements are blocked. A greylist contains items that are temporarily blocked (or temporarily allowed) until an additional step is performed.}}

</ref> and OS/2<ref name=“os2bmp”>

</ref> operating systems.}}

used in a

</ref>}}

, representing a

. Historically, the byte was the number of bits used to encode a single character of text in a computer<ref name=“Buchholz_1962”>

</ref> and for this reason it is the smallest addressable unit of

in many

.}}

. There, a small program is stored called firmware. It does power-on self-tests and, most importantly, allows access to other types of memory like a hard disk and main memory. The firmware loads bigger programs into the computer's main memory and runs it.}}

</ref>}}

that carries out the

of a

by performing the basic arithmetic, logic, controlling, and

(I/O) operations specified by the instructions. The computer industry has used the term “central processing unit” at least since the early 1960s.<ref name=“weik1961”>

(CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.<ref name=“kuck”>

</ref>}}

</ref>}}

, an

for performing encryption or decryption&mdash;a series of well-defined steps that can be followed as a

.}}

, an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods).

}} In many languages, the class name is used as the name for the class (the template itself), the name for the default constructor of the class (a

that creates objects), and as the type of objects generated by instantiating the class; these distinct concepts are easily conflated.

}}}}

(OOP) in which inheritance occurs via defining “

” of

, instead of via the objects alone (compare prototype-based programming).}}

</ref> The focus of the cleanroom process is on defect prevention, rather than defect removal.}}

together with an environment.<ref>Sussman and Steele. “Scheme: An interpreter for extended lambda calculus”. “… a data structure containing a lambda expression, and an environment to be used when that lambda expression is applied to arguments.” (Wikisource)</ref>}}

, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and

,

,

or

specifications. In IBM's OS/360 and its successors they are referred to as partitioned data sets.}}

for accomplishing a specific

task. Programming involves tasks such as analysis, generating

, profiling algorithms' accuracy and resource consumption, and the implementation of algorithms in a chosen

(commonly referred to as coding<ref name=“tumblr2014”>

</ref><ref name=“tumblr1”>

</ref>). The

of a program is written in one or more programming languages. The purpose of programming is to find a sequence of instructions that will automate the performance of a task for solving a given problem. The process of programming thus often requires expertise in several different subjects, including knowledge of the

, specialized algorithms, and formal logic.}}

,

, error detection and correction, data transmission and data storage. Codes are studied by various scientific disciplines—such as information theory, electrical engineering, mathematics, linguistics, and

—for the purpose of designing efficient and reliable data transmission methods. This typically involves the removal of redundancy and the correction or detection of errors in the transmitted data.}}

. Each record consists of one or more

, separated by commas. The use of the comma as a field separator is the source of the name for this file format.}}

that transforms computer code written in one

from a high-level programming language to a lower-level language (e.g. assembly language, object code, or machine code) to create an

program.<ref>

</ref>}}

, and of the theory of computation that originated in the 1930s with the study of computable functions and Turing degrees. The field has since expanded to include the study of generalized computability and definability. In these areas, recursion theory overlaps with proof theory and effective descriptive set theory.}}

</ref> that includes both arithmetical and non-arithmetical steps and follows a well-defined model, e.g. an

. The study of computation is paramount to the discipline of

.}}

, to calculate the structures and properties of molecules and solids.}}

which focuses on classifying computational problems according to their inherent difficulty, and relating these classes to each other. A computational problem is a task solved by a computer. A computation problem is solvable by mechanical application of mathematical steps, such as an

.}}

that requires extensive computational resources to study the behavior of a complex system by computer simulation.<ref>

</ref>}}

</ref><ref>What is computational neuroscience? Patricia S. Churchland, Christof Koch, Terrence J. Sejnowski. in Computational Neuroscience pp.46-55. Edited by Eric L. Schwartz. 1993. MIT Press

</ref><ref>

</ref><ref>

</ref>}}

.</ref> Historically, computational physics was the first application of modern computers in science, and is now a subset of computational science.}}

. Modern computers have the ability to follow generalized sets of operations, called

. These programs enable computers to perform an extremely wide range of tasks.}}

systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer but not a particular implementation.<ref>

</ref> In other definitions computer architecture involves instruction set architecture design, microarchitecture design, logic design, and implementation.<ref>

</ref>}}

components and recording media that are used to retain digital data. Data storage is a core function and fundamental component of all modern computer systems.<ref>name=“Patterson”>

</ref>

}}

</ref>}}

.}}

</ref> that can be executed by a computer to perform a specific task. }}

for accomplishing a specific

task. Programming involves tasks such as analysis, generating

, profiling algorithms' accuracy and resource consumption, and the implementation of algorithms in a chosen

(commonly referred to as coding<ref name=“tumblr2014”/><ref name=“tumblr1”/>). The

of a program is written in one or more programming languages. The purpose of programming is to find a sequence of instructions that will automate the performance of a task for solving a given problem. The process of programming thus often requires expertise in several different subjects, including knowledge of the

, specialized algorithms, and formal logic.}}

. It involves the study of

that process, store, and communicate digital information. A

specializes in the theory of

and the design of computational systems.<ref>

</ref>}}

, the study of the theoretical foundations of information and computation and their application.<ref>

</ref>}}

</ref> or information technology security (IT security).}}

, or electronic data, as well as from disruption or misdirection of the services they provide.}}

.</ref><ref>Huang, T. (1996-11-19). Vandoni, Carlo, E, ed. Computer Vision : Evolution And Promise (PDF). 19th CERN School of Computing. Geneva: CERN. pp. 21–25. doi:10.5170/CERN-1996-008.21.

.</ref><ref>Milan Sonka; Vaclav Hlavac; Roger Boyle (2008). Image Processing, Analysis, and Machine Vision. Thomson.

.</ref>}}

</ref>}}

</ref>}}

which performs different computations or actions depending on whether a programmer-specified Boolean condition evaluates to true or false. Apart from the case of branch predication, this is always achieved by selectively altering the

based on some condition.}}

in which

is passed explicitly in the form of a continuation. This is contrasted with direct style, which is the usual style of programming. Gerald Jay Sussman and Guy L. Steele, Jr. coined the phrase in AI Memo 349 (1975), which sets out the first version of the Scheme programming language.<ref>

</ref><ref>

</ref>}}

</ref> The organization has released several copyright-licenses, known as Creative Commons licenses, free of charge to the public.}}

</ref> More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages;<ref name=“modern-crypto”>

</ref> various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation<ref name=“hac”>

</ref> are central to modern cryptography. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, electrical engineering, communication science, and physics. Applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.}}

or is embedded in the

. It either explains how it operates or how to use it, and may mean different things to people in different roles.}}

</ref>}}

or to a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. By providing a worldwide, distributed directory service, the Domain Name System has been an essential component of the functionality of the Internet since 1985.}}

point.}}

</ref> such as a web server, an FTP server, an email server, or other similar systems. This contrasts with

</ref> Modern encryption schemes utilize the concepts of public-key and symmetric-key.<ref name=“:1” /> Modern encryption techniques ensure security because modern computers are inefficient at cracking the encryption.}}

in which the

is determined by

such as user actions (mouse clicks, key presses), sensor outputs, or messages from other programs or

. Event-driven programming is the dominant paradigm used in graphical user interfaces and other applications (e.g. JavaScript web applications) that are centered on performing certain actions in response to

. This is also true of programming for device drivers (e.g. P in USB device driver stacks<ref>

</ref>).}}

for global optimization inspired by biological evolution, and the subfield of

and

studying these algorithms. In technical terms, they are a family of population-based trial-and-error problem-solvers with a metaheuristic or stochastic optimization character.}}

</ref> as opposed to a data file that must be parsed by a program to be meaningful. The exact interpretation depends upon the use - while “instructions” is traditionally taken to mean machine code instructions for a physical CPU, in some contexts a file containing bytecode or scripting language instructions may also be considered executable.}}

. It is provided by specialized

constructs, computer hardware mechanisms like interrupts, or operating system IPC facilities like signals.}}

, a combination of one or more

,

,

, and

that the programming language interprets (according to its particular rules of precedence and of association) and computes to produce (“to return”, in a

environment) another value. This process, as for mathematical expressions, is called evaluation.}}

. Originally, it addressed zero-sum games, in which each participant's gains or losses are exactly balanced by those of the other participants. Today, game theory applies to a wide range of behavioral relations, and is now an umbrella term for the science of logical decision making in humans, animals, and computers.}}

, in which a poorly written program might produce nonsensical behavior.}}

. The unit symbol for the gigabyte is GB.}}

, a variable with global

, a hash table (hash map) is a data structure that implements an associative array abstract data type, a structure that can map keys to

<!–DOI for chapter–></ref>}}

, behavioral sciences, design, media studies, and several other fields of study.}}

that uses

that change a program's

. In much the same way that the imperative mood in natural languages expresses commands, an imperative program consists of

with the iterative philosophy of prototyping.}}

, for locating and assessing

for team-centric efforts.}}

, the mechanism of basing an

or

upon another object (prototype-based inheritance) or class (class-based inheritance), retaining similar implementation. Also defined as deriving new classes (sub classes) from existing ones (super class or base class) and forming them into a hierarchy of classes.}}

, and the outside world, possibly a human or another information processing system. Inputs are the signals or data received by the system and outputs are the signals or data sent from it. The term can also be used as part of an action; to “perform I/O” is to perform an input or output operation.}}

(CPU) follows from

until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.}}

</ref> It occurs after unit testing and before validation testing. Integration testing takes as its input modules that have been unit tested, groups them in larger aggregates, applies tests defined in an integration test plan to those aggregates, and delivers as its output the integrated system ready for system testing.<ref>Martyn A Ould & Charles Unwin (ed), ''Testing in Software Development'', BCS (1986), p71. Accessed 31 Oct 2014</ref>}}

</ref><ref>

Fact Sheets on the European Union|publisher=European Parliament|access-date=2018-12-06}}</ref> There are many types of intellectual property, and some countries recognize more than others.<ref>

</ref><ref>

</ref><ref>

</ref> The most well-known types are copyrights, patents, trademarks, and trade secrets.}}

</ref> Intelligent agents may also learn or use knowledge to achieve their goals. They may be very simple or very complex. A reflex machine, such as a thermostat, is considered an example of an intelligent agent.<ref>According to the definition given by

</ref>}}

, computer hardware, peripheral devices, humans, and combinations of these.<ref name=“HookwayInterface14”>

</ref> Some computer hardware devices, such as a touchscreen, can both send and receive data through the interface, while others such as a mouse or microphone may only provide an interface to send data to a given system.<ref>

</ref>}}

is said to have Internal Documentation if the notes on how and why various parts of code operate is included within the

as comments. It is often combined with meaningful variable names with the intention of providing potential future programmers a means of understanding the workings of the code. This contrasts with external documentation, where programmers keep their notes and explanations in a separate document.}}

that runs automated tasks (scripts) over the Internet.<ref>

that directly

instructions written in a

or scripting language, without requiring them to have been previously

into a machine language program.}}

that is class-based,

</ref>), and designed to have as few implementation

as possible. It is intended to let application developers “write once, run anywhere” (WORA),<ref>

</ref> meaning that

Java code can run on all platforms that support Java without the need for recompilation.<ref name=“design_goals”>

</ref>}}

, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and

,

,

, or

specifications.}}

. It sequentially checks each element of the list until a match is found or the whole list has been searched.

}}

</ref>}}

, where the same value may occur more than once. An instance of a list is a computer representation of the mathematical concept of a finite sequence; the (potentially) infinite analog of a list is a

.<ref>

</ref>

Lists are a basic example of

, as they contain other values. If the same value occurs multiple times, each occurrence is considered a distinct item.}}

, a bug in a program that causes it to operate incorrectly, but not to terminate abnormally (or crash). A logic error produces unintended or undesired output or other behaviour, although it may not immediately be recognized as such.}}

which is largely based on formal logic. Any program written in a logic

is a set of sentences in logical form, expressing facts and rules about some problem domain. Major logic programming language families include Prolog, answer set programming (ASP), and Datalog.}}

</ref>}}

.<ref>

</ref> In a general sense object code is a sequence of statements or instructions in a computer language,<ref>

</ref> usually a machine code language (i.e., binary) or an intermediate language such as register transfer language (RTL). The term indicates that the code is the goal or result of the compiling process, with some early sources referring to source code as a “subject program.”}}

, as well as using visual modeling throughout the software development process to guide stakeholder communication and product quality.}}

based on the concept of “objects”, which can contain data, in the form of

</ref><ref>

, section 1.6 “Object-Oriented Programming”</ref> OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of

, which also determine their types.}}

in which

is released under a license in which the copyright holder grants users the rights to study, change, and distribute the software to anyone and for any purpose.<ref>

</ref> Open-source software may be developed in a collaborative public manner. Open-source software is a prominent example of open collaboration.<ref name=“Open Collaboration”>

</ref>}}

resources, and provides common

for

.}}

</ref> Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer.<ref>

</ref>}}

</ref> reviews each line of code as it is typed in. The two programmers switch roles frequently.}}

in which many calculations or the execution of processes are carried out simultaneously.<ref>

</ref> Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different forms of parallel computing: bit-level, instruction-level, data, and task parallelism.}}

, a special kind of variable, used in a

to refer to one of the pieces of data provided as input to the subroutine.

being discussed.}} These pieces of data are the values<ref>

</ref><ref>

</ref><ref>

, a condition or predicate that must always be true just after the execution of some section of code or after an operation in a formal specification. Postconditions are sometimes tested using assertions within the code itself. Often, postconditions are simply included in the documentation of the affected section of code.}}

, a condition or predicate that must always be true just prior to the execution of some section of code or before an operation in a formal specification. If a precondition is violated, the effect of the section of code becomes undefined and thus may or may not carry out its intended work. Security problems can arise due to incorrect preconditions.}}

or

data structure, but where additionally each element has a “priority” associated with it. In a priority queue, an element with high priority is served before an element with low priority. In some implementations, if two elements have the same priority, they are served according to the order in which they were enqueued, while in other implementations, ordering of elements with the same priority is undefined.}}

Subroutines may be defined within programs, or separately in libraries that can be used by many programs. In different programming languages, a subroutine may be called a routine, subprogram, function, method, or procedure. Technically, these terms all have different definitions. The generic, umbrella term callable unit is sometimes used.<ref name=“U.S. Election Assistance Commission 2007”>

</ref>}}

undergoes, from initial creation to deployment and execution. The phases are edit time, compile time, link time, distribution time, installation time, load time, and run time.}}

to implement

.}}

</ref>}}

</ref><ref name=Bratko2012>

</ref><ref name=Covington1994>

.</ref>}}

. A quantum computer is used to perform such computation, which can be implemented theoretically or physically.<ref name=2018Report>

</ref>

}}

R Foundation

The R Core Team asks authors who use R in their data analysis to cite the software using:

• R Core Team (2016). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org/.

}} The R language is widely used among statisticians and data miners for developing statistical software

}} and data analysis.<ref>

</ref>}}

that is the standard in

, the radix is two, because it uses only two digits, 0 and 1, to uniquely specify each number.}}

</ref><ref name=“Radványi”>

</ref><ref name=“Kahate”>

</ref><ref>

</ref>}}

, where a function being defined is applied within its own definition. While this apparently defines an infinite number of instances (function values), it is often done in such a way that no infinite loop or infinite chain of references can occur.}}

,

, or

to a resource, such as an object, a block of memory, disk space, and others. In garbage collection algorithms, reference counts may be used to deallocate objects which are no longer needed.}}

</ref>

}}

</ref> Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time.}}

</ref>) is re-running functional and non-functional tests to ensure that previously developed and tested software still performs after a change.<ref>

</ref>).}}

</ref>}}

, and others. Robotics involves design, construction, operation, and use of robots, as well as computer systems for their perception, control, sensory feedback, and information processing. The goal of robotics is to design intelligent machines that can help and assist humans in their day-to-day lives and keep everyone safe.}}

</ref>}}

using exact arithmetic and the result produced by the same algorithm using finite-precision, rounded arithmetic.<ref name=“Forrester_2018”>

</ref> Rounding errors are due to inexactness in the representation of real numbers and the arithmetic operations done with them. This is a form of quantization error.<ref>

</ref> When using approximation equations or algorithms, especially when using finitely many digits to represent real numbers (which in theory have infinitely many digits), one of the goals of numerical analysis is to estimate computation errors.<ref>

</ref> Computation errors, also called numerical errors, include both truncation errors and roundoff errors.<ref>

</ref>}}

</ref>}}

s life cycle, in which the code is being executed on the computer's central processing unit (CPU) as machine code. In other words, “runtime” is the running phase of a program.}}

which solves the search problem, namely, to retrieve information stored within some data structure, or calculated in the search space of a problem

, either with discrete or continuous values.}}

</ref><ref name=Weikum01>Gerhard Weikum, Gottfried Vossen (2001): ''Transactional Information Systems'', Elsevier,

</ref> When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object. For many complex objects, such as those that make extensive use of references, this process is not straightforward. Serialization of object-oriented objects does not include any of their associated methods with which they were previously linked.

This process of serializing an object is also called marshalling an object in some situations.://www.ruby-doc.org/core/classes/Marshal.html://caml.inria.fr/pub/docs/manual-ocaml/libref/Marshal.html The opposite operation, extracting a data structure from a series of bytes, is deserialization, (also called unserialization or unmarshalling).}}

</ref><ref>

</ref>}}

.</ref> Software design may refer to either “all the activity involved in conceptualizing, framing, implementing, commissioning, and ultimately modifying complex systems” or “the activity following requirements specification and before programming, as … [in] a stylized software engineering process.”<ref>

</ref>}}

</ref> Therefore, software development may include research, new development, prototyping, modification, reuse, re-engineering, maintenance, or any other activities that result in software products.<ref>

</ref>}}

</ref><ref name=“ACM 2020”>

</ref><ref name=“Laplante 2007”>

</ref> Software engineering is a computing discipline.<ref>

</ref>}}

</ref>}}

</ref> Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include the process of executing a program or application with the intent of finding software bugs (errors or other defects), and verifying that the software product is fit for use. }}

, which adds an element to the collection, and

• , which removes the most recently added element that was not yet removed.

The order in which elements come off a stack gives rise to its alternative name, LIFO (last in, first out). Additionally, a peek operation may give access to the top without modifying the stack.<ref>By contrast, a simple QUEUE operates FIFO (first in, first out).</ref> The name “stack” for this type of structure comes from the analogy to a set of physical items stacked on top of each other. This structure makes it easy to take an item off the top of the stack, while getting to an item deeper in the stack may require taking off multiple other items first.<ref name=“clrs_pages_232-233”>

</ref>}}

</ref> the remembered information is called the state of the system.}}

</ref> A program written in such a language is formed by a sequence of one or more statements. A statement may have internal components (e.g., expressions).}}

</ref>

}}

</ref><ref>

</ref> NoSQL databases are increasingly used in big data and real-time web applications.<ref>

</ref> NoSQL systems are also sometimes called “Not only SQL” to emphasize that they may support SQL-like query languages or sit alongside SQL databases in polyglot-persistent architectures.<ref>

</ref><ref>

</ref>}}

Subroutines may be defined within programs, or separately in libraries that can be used by many programs. In different programming languages, a subroutine may be called a routine, subprogram, function, method, or procedure. Technically, these terms all have different definitions. The generic, umbrella term callable unit is sometimes used.<ref name=“U.S. Election Assistance Commission 2007”>

</ref>}}

}}

</ref>

although many people use the two terms interchangeably.

Thus

<nowiki>http:</nowiki>//www.example.com

is a URL, while

www.example.com

is not.<ref>

</ref>}} URLs occur most commonly to reference web pages (http), but are also used for file transfer (ftp), email (mailto), database access (JDBC), and many other applications.}}

</ref> Power users use advanced features of programs, though they are not necessarily capable of computer programming and system administration.}}

) that acts on behalf of a

, such as a web browser that “retrieves, renders and facilitates end user interaction with Web content”.<ref>

</ref> An email reader is a mail user agent.}}

for machines and

, such as computers, home appliances, mobile devices, and other electronic devices, with the focus on maximizing usability and the user experience. The goal of user interface design is to make the user's interaction as simple and efficient as possible, in terms of accomplishing user goals (user-centered design).}}

the stored value, in addition to referring to the variable itself, depending on the context. This separation of name and content allows the name to be used independently of the exact information it represents. The identifier in computer

can be bound to a value during run time, and the value of the variable may therefore change during the course of

.<ref>

</ref><ref>

</ref>}}

of a computer system. Virtual machines are based on

and attempt to provide the same functionality as a physical computer. Their implementations may involve specialized hardware, software, or a combination of both.}}

, and is an example of the more general V-model. Instead of moving down in a linear way, the process steps are bent upwards after the

phase, to form the typical V shape. The V-Model demonstrates the relationships between each phase of the development life cycle and its associated phase of testing. The horizontal and vertical axes represent time or project completeness (left-to-right) and level of abstraction (coarsest-grain abstraction uppermost), respectively.<ref>Kevin Forsberg and Harold Mooz, “The Relationship of System Engineering to the Project Cycle”, in Proceedings of the First Annual Symposium of National Council on System Engineering, October 1991: 57–65.</ref>}}