A diagram is a symbolic

representation Representation may refer to: Law and politics *Representation (politics), political activities undertaken by elected representatives, as well as other theories ** Representative democracy, type of democracy in which elected officials represent a ...

of information using visualization techniques. Diagrams have been used since prehistoric times on walls of caves, but became more prevalent during the

Enlightenment Enlightenment or enlighten may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing (alphabetically by country or culture): ...

. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word '' graph'' is sometimes used as a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

for diagram.

Overview

The term "diagram" in its commonly used sense can have a general or specific meaning: * ''visual information device'' : Like the term "

illustration An illustration is a decoration, interpretation or visual explanation of a text, concept or process, designed for integration in print and digital published media, such as posters, flyers, magazines, books, teaching materials, animations, vid ...

", "diagram" is used as a collective term standing for the whole class of technical genres, including graphs, technical drawings and tables. * ''specific kind of visual display'' : This is the genre that shows qualitative data with shapes that are connected by lines, arrows, or other visual links. In science the term is used in both ways. For example, Anderson (1997) stated more generally: "diagrams are pictorial, yet abstract, representations of information, and maps, line graphs, bar charts, engineering blueprints, and architects' sketches are all examples of diagrams, whereas photographs and video are not".Michael Anderson (1997). "Introduction to Diagrammatic Reasoning," at ''cs.hartford.edu.'' Retrieved 21 July 2008. On the other hand, Lowe (1993) defined diagrams as specifically "abstract graphic portrayals of the subject matter they represent". In the specific sense diagrams and charts contrast with computer graphics, technical illustrations, infographics, maps, and technical drawings, by showing "abstract rather than

literal Literal may refer to: * Interpretation of legal concepts: ** Strict constructionism ** The plain meaning rule (a.k.a. "literal rule") * Literal (mathematical logic), certain logical roles taken by propositions * Literal (computer programmin ...

representations of information". The essence of a diagram can be seen as: * a ''form'' of visual

format Format may refer to: Printing and visual media * Text formatting, the typesetting of text elements * Paper formats, or paper size standards * Newspaper format, the size of the paper page Computing * File format, particular way that informati ...

ting devices * a ''display'' that does not show quantitative data (numerical data), but rather relationships and abstract information * with ''building blocks'' such as geometrical shapes connected by

line Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...

arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers c ...

s, or other visual links. Or in Hall's (1996) words "diagrams are simplified figures, caricatures in a way, intended to convey essential meaning".Bert S. Hall (1996). "The Didactic and the Elegant: Some Thoughts on Scientific and Technological Illustrations in the Middle Ages and Renaissance". in: B. Braigie (ed.) ''Picturing knowledge: historical and philosophical problems concerning the use of art in science''. Toronto: University of Toronto Press. p.9 These simplified figures are often based on a set of rules. The basic shape according to White (1984) can be characterized in terms of "elegance, clarity, ease, pattern, simplicity, and validity". Elegance is basically determined by whether or not the diagram is "the simplest and most fitting solution to a problem".

Diagrammatology

Diagrammatology Diagrammatology is the academic study of diagrams. It studies fundamental role played by the diagram in the communication and creation of knowledge. Diagrammatology is not only an interdisciplinary subject, but pan-historical and cross-cultural. ...

is the academic study of diagrams. Scholars note that while a diagram may look similar to the thing that it represents, this is not necessary. Rather a diagram may only have

structural similarity The structural similarity index measure (SSIM) is a method for predicting the perceived quality of digital television and cinematic pictures, as well as other kinds of digital images and videos. SSIM is used for measuring the similarity between tw ...

to what it represents, an idea often attributed to Charles Sanders Peirce. Structural similarity can be defined in terms of a mapping between parts of the diagram and parts of what the diagram represents and the properties of this mapping, such as maintaining relations between these parts and facts about these relations. This is related to the concept of isomorphism, or homomorphism in mathematics. Sometimes certain

geometric Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ca ...

properties (such as which points are closer) of the diagram can be mapped to properties of the thing that a diagram represents. On the other hand the representation of an object in a diagram may be overly specific and properties that are true in the diagram may not be true for the object the diagram represents. A diagram may act as a means of cognitive extension allowing

reasoning Reason is the capacity of consciously applying logic by drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activities as philosophy, science, lang ...

to take place on the diagram based on which constraints are similar.

Gallery of diagram types

There are at least the following types of diagrams: * Logical or conceptual diagrams, which take a collection of items and relationships between them, and express them by giving each item a 2D position, while the relationships are expressed as connections between the items or overlaps between the items, for example: * Quantitative diagrams, which display a relationship between two variables that take either discrete or a continuous range of values; for example: * Schematics and other types of diagrams, for example: Many of these types of diagrams are commonly generated using diagramming software such as Visio and Gliffy. Diagrams may also be classified according to use or purpose, for example, explanatory and/or how to diagrams. Thousands of diagram techniques exist. Some more examples follow:

Specific diagram types

;A * Activity diagram used in UML 6/9 and SysML ;B * Bachman diagram * Booch – used in software engineering * Bow-tie diagram * Block diagram *

Block definition diagram (BDD) Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...

used in SysML ;C * Carroll diagram * Cartogram * Catalytic cycle * Computer network diagram * Chemical equation * Curly arrow diagram * Category theory diagrams *

Cause-and-effect diagram Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams) are causal diagrams created by Kaoru Ishikawa that show the potential causes of a specific event. Common uses of the Ishikawa diagram are product ...

Chord diagram (disambiguation) A chord diagram may refer to: * Chord diagram (music), a diagram showing the fingering of a chord on a guitar or other fretted musical instrument *Chord diagram (information visualization), a diagram showing a many-to-many relationship between objec ...

* Circuit diagram * Class diagram – from UML 1/9 *

Cobweb diagram A cobweb plot, or Verhulst diagram is a visual tool used in the dynamical systems field of mathematics to investigate the qualitative behaviour of one-dimensional iterated functions, such as the logistic map. Using a cobweb plot, it is possible t ...

Collaboration diagram A communication diagram in the Unified Modeling Language (UML) 2.0, is a simplified version of the UML 1.x collaboration diagram. UML has four types of interaction diagrams: * Sequence diagram * Communication diagram * Interaction overview di ...

– from

UML 2.0 The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. The creation of UML was originally ...

* Communication diagram – from

Commutative diagram 350px, The commutative diagram used in the proof of the five lemma. In mathematics, and especially in category theory, a commutative diagram is a diagram such that all directed paths in the diagram with the same start and endpoints lead to the s ...

* Comparison diagram * Component diagram – from UML 3/9 * Composite structure diagram – from

* Concept map * Constellation diagram * Context diagram * Control flow diagram * Contour diagram * Cordier diagram *

Cross functional flowchart A deployment flowchart (sometimes referred to as a cross functional flowchart) is a business process mapping tool used to articulate the steps and Project stakeholder, stakeholders of a given business process, process. "Deployment flowcharts con ...

;D * Data model diagram * Data flow diagram * Data structure diagram *

Dendrogram A dendrogram is a diagram representing a tree. This diagrammatic representation is frequently used in different contexts: * in hierarchical clustering, it illustrates the arrangement of the clusters produced by the corresponding analyses. ...

Dependency diagram In mathematics, computer science and digital electronics, a dependency graph is a directed graph representing dependencies of several objects towards each other. It is possible to derive an evaluation order or the absence of an evaluation order t ...

* Deployment diagram – from UML 9/9 * Dynkin diagram *

Dot and cross diagram Lewis structures, also known as Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDS), are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons tha ...

Double bubble map David Hyerle is an author and creator of a thought-organization methodology called "Thinking Maps" that is popular in public schools in the United States. Thinking Maps In 1988, David Hyerle wrote ''Expand Your Thinking'' and introduced Thinki ...

– used in education *

Drakon-chart DRAKON is a free and open source algorithmic visual programming and modeling language developed within the Buran space project following ergonomic design principles. The language provides a uniform way to represent flowcharts of any com ...

;E * Entity-relationship diagram (ERD) * Event-driven process chain * Euler diagram * Eye diagram – a diagram of a received telecommunications signal *

Exploded-view drawing An exploded-view drawing is a diagram, picture, schematic or technical drawing of an object, that shows the relationship or order of assembly of various parts. It shows the components of an object slightly separated by distance, or suspended in ...

* Express-G * Extended functional flow block diagram (EFFBD) ;F * Family tree * Feynman diagram * Flow chart * Flow process chart * Flow diagram *

Fusion diagram Fusion, or synthesis, is the process of combining two or more distinct entities into a new whole. Fusion may also refer to: Science and technology Physics *Nuclear fusion, multiple atomic nuclei combining to form one or more different atomic nuc ...

* Free body diagram ;G * Gantt chart – shows the timing of tasks or activities (used in project management) *

Grotrian diagram A Grotrian diagram, or term diagram, shows the allowed electronic transitions between the energy levels of atoms. They can be used for one-electron and multi-electron atoms. They take into account the specific selection rules related to change ...

* Goodman diagram – shows the

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

data (example: for a wind turbine blades) ;H * Hasse diagram * HIPO diagram ;I *

Internal block diagram (IBD) Internal may refer to: * Internality as a concept in behavioural economics * Neijia, internal styles of Chinese martial arts * Neigong or "internal skills", a type of exercise in meditation associated with Daoism *'' Internal (album)'' by Safia, 20 ...

used in SysML * IDEF0 * IDEF1 (entity relations) *

Interaction overview diagram Interaction Overview Diagram is one of the fourteen types of diagrams of the Unified Modeling Language (UML), which can picture a control flow with nodes that can contain interaction diagrams. The interaction overview diagram is similar to the ...

– from

UML The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. The creation of UML was originally ...

* Ishikawa diagram ;J * Jackson diagram * Jones diagram ;K * Karnaugh map *

Kinematic diagram In mechanical engineering, a kinematic diagram or kinematic scheme (also called a joint map or skeleton diagram) illustrates the connectivity of Linkage (mechanical), links and Mechanical joint, joints of a mechanism (engineering), mechanism or ...

Knot diagram In the mathematical field of topology, knot theory is the study of mathematical knots. While inspired by knots which appear in daily life, such as those in shoelaces and rope, a mathematical knot differs in that the ends are joined so it cannot ...

;L * Ladder diagram * Levi graph * Line of balance * Link grammar diagram ;M * Martin ERD * Message sequence chart * Mind map – used for learning, brainstorming, memory, visual thinking and problem solving * Minkowski spacetime diagram * Molecular orbital diagram * Motion diagram ;N * N2 *

Nassi–Shneiderman diagram A Nassi–Shneiderman diagram (NSD) in computer programming is a graphical design representation for structured programming. This type of diagram was developed in 1972 by Isaac Nassi and Ben Shneiderman who were both graduate students at Ston ...

or structogram – a representation for

structured programming Structured programming is a programming paradigm aimed at improving the clarity, quality, and development time of a computer program by making extensive use of the structured control flow constructs of selection ( if/then/else) and repetition ( ...

* Nomogram * Network diagram ;O * Object diagram – from UML 2/9 * Organigram * Onion diagram – also known as "stacked Venn diagram" ;P *

Package diagram A package diagram in the Unified Modeling Language depicts the dependencies between the packages that make up a model. Overview In addition to the standard UML Dependency relationship, there are two special types of dependencies defined betwe ...

from UML 4/9 and SysML * Parametric diagram from SysML * PERT * Petri net – shows the structure of a distributed system as a directed

bipartite graph In the mathematical field of graph theory, a bipartite graph (or bigraph) is a graph whose vertices can be divided into two disjoint and independent sets U and V, that is every edge connects a vertex in U to one in V. Vertex sets U and V are ...

with annotations *

Phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

- represents a phylogeny (evolutionary relationships among groups of organisms) * Piping and instrumentation diagram (P&ID) *

Phase diagram A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct phases (such as solid, liquid or gaseous ...

used to present solid/liquid/gas information * Plant diagram * Pressure volume diagram used to analyse engines * Pourbaix diagram *

Process flow diagram A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between ''major'' equipment of a plant facility and does n ...

or PFD – used in chemical engineering *

Program structure diagram Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * Program, a part of planning Arts and entertainment Audio * Progra ...

;R * Radar chart * Radial diagram *

Requirement diagram A requirement diagram is a diagram specially used in SysML in which requirement In product development and process optimization, a requirement is a singular documented physical or functional need that a particular design, product or process aims ...

Used in SysML *

Rich picture __NOTOC__ Part of the soft systems methodology, rich pictures provide a mechanism for learning about complex or ill-defined problems by drawing detailed ("rich") representations of them. Typically, rich pictures follow no commonly agreed syntax, us ...

R-diagram A Randolph diagram (R-diagram) is a simple way to visualize logical expressions and combinations of sets. Randolph diagrams were created by mathematician John F. Randolph in 1965, while he was teaching at the University of Arkansas. Overview R ...

* Routing diagram ;S * Sankey diagram – represents material, energy or cost flows with quantity proportional arrows in a process network * Sentence diagram – represents the

grammatical In linguistics, grammaticality is determined by the conformity to language usage as derived by the grammar of a particular variety (linguistics), speech variety. The notion of grammaticality rose alongside the theory of generative grammar, the go ...

structure of a

natural language In neuropsychology, linguistics, and philosophy of language, a natural language or ordinary language is any language that has evolved naturally in humans through use and repetition without conscious planning or premeditation. Natural languages ...

sentence * Sequence diagram from UML 8/9 and SysML * SDL/GR diagram – specification and description Language. SDL is a formal language used in computer science. * Smith chart * Spider chart * Spray diagram * SSADM – structured systems analysis and design methodology (used in software engineering) *

Star chart A star chart is a celestial map of the night sky with astronomical objects laid out on a grid system. They are used to identify and locate constellations, stars, nebulae, galaxies, and planets. They have been used for human navigation since ...

Celestial sphere In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, ...

* State diagram are used for state machines in software engineering from UML 7/9 * Swim lane * Syntax diagram used in software engineering to represent a

context-free grammar In formal language theory, a context-free grammar (CFG) is a formal grammar whose production rules are of the form :A\ \to\ \alpha with A a ''single'' nonterminal symbol, and \alpha a string of terminals and/or nonterminals (\alpha can be empt ...

* Systems Biology Graphical Notation – a graphical notation used in diagrams of biochemical and cellular processes studied in

systems biology Systems biology is the computational modeling, computational and mathematical analysis and modeling of complex biological systems. It is a biology-based interdisciplinary field of study that focuses on complex interactions within biological syst ...

* System context diagram * System structure * Systematic layout planning ;T *Timing diagram: digital timing diagram *Timing diagram:

* TQM Diagram * Tree structure * Treemap ;U * UML diagram – Unified Modeling Language (used in software engineering) * Use case diagram – from UML 5/9 and SysML ;V * Value stream mapping * Venn diagram * Violin plot * Voronoi diagram ;W * Warnier-Orr * Wedge-dash diagram * Williot diagram ;Y * Yourdon-Coad – see Edward Yourdon, used in software engineering

Overview

Diagrammatology

Gallery of diagram types

Specific diagram types

See also

References

Further reading