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 Projected is an American rock supergroup consisting of Sevendust members John Connolly and Vinnie Hornsby, Alter Bridge and Creed drummer Scott Phillips, and former Submersed and current Tremonti guitarist Eric Friedman. The band released thei ...

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 Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties *Graph (topology), a topological space resembling a graph in the sense of discre ...

, 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 informatio ...

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 Continuity or continuous may refer to: Mathematics * Continuity (mathematics), the opposing concept to discreteness; common examples include ** Continuous probability distribution or random variable in probability and statistics ** 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 Gliffy is software for diagramming via an HTML5 cloud-based app. It is used to create UML diagrams, floor plans, Venn diagrams, flowcharts and various other kinds of diagrams online. Gliffy diagrams can be shared with and edited by users in real tim ...

. 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 method, Booch – used in software engineering *Bow-tie diagram *Block diagram *Block definition diagram (BDD) used in SysML ;C *Carroll diagram *Cartogram *Catalytic cycle *Computer network diagram *Chemical equation *Arrow pushing, Curly arrow diagram *Diagram (category theory), Category theory diagrams *Cause-and-effect diagram *Chord diagram (disambiguation) *Circuit diagram *Class diagram – from Unified Modeling Language, UML 1/9 *Cobweb diagram *Communication diagram, Collaboration diagram – from Unified Modeling Language, UML 2.0 *Communication diagram – from Unified Modeling Language, UML 2.0 *Commutative diagram *Comparison diagram *Component diagram – from Unified Modeling Language, UML 3/9 *Composite structure diagram – from Unified Modeling Language, UML 2.0 *Concept map *Constellation diagram *Context diagram *Control flow diagram *Contour diagram *Cordier diagram *Cross functional flowchart ;D *Data model diagram *Data flow diagram *Data structure diagram *Dendrogram *Dependency diagram *Deployment diagram – from Unified Modeling Language, UML 9/9 *Dynkin diagram *Dot and cross diagram *Double bubble map – used in education *DRAKON, Drakon-chart ;E *Entity-relationship diagram (ERD) *Event-driven process chain *Euler diagram *Eye diagram – a diagram of a received telecommunications signal *Exploded-view drawing *Express-G *Extended functional flow block diagram (EFFBD) ;F *Family tree *Feynman diagram *Flow chart *Flow process chart *Flow diagram *Fusion diagram *Free body diagram ;G *Gantt chart – shows the timing of tasks or activities (used in project management) *Grotrian diagram *Goodman diagram – shows the fatigue (material), fatigue data (example: for a wind turbine blades) ;H *Hasse diagram *HIPO diagram ;I *Internal block diagram (IBD) used in SysML *IDEF0 *IDEF1 (entity relations) *Interaction overview diagram – from Unified Modeling Language, UML *Ishikawa diagram ;J *Jackson Structured Programming, Jackson diagram *Jones diagram ;K *Karnaugh map *Kinematic diagram *Knot diagram ;L *Ladder logic, Ladder diagram *Levi graph *Line of balance *Link grammar, Link grammar diagram ;M *Martin ERD *Message sequence chart *Mind map – used for learning, brainstorming, memory, visual thinking and problem solving *Minkowski diagram, Minkowski spacetime diagram *Molecular orbital diagram *Motion diagram ;N *N2 diagram, N2 *Nassi–Shneiderman diagram or structogram – a representation for structured programming *Nomogram *Network diagram ;O *Object diagram – from Unified Modeling Language, UML 2/9 *Organigram *Onion model, Onion diagram – also known as "stacked Venn diagram" ;P *Package diagram from Unified Modeling Language, UML 4/9 and SysML *Parametric diagram from SysML *PERT *Petri net – shows the structure of a distributed system as a directed bipartite graph with annotations *Phylogenetic tree - represents a phylogeny (evolutionary relationships among groups of organisms) *Piping and instrumentation diagram (P&ID) *Phase diagram used to present solid/liquid/gas information *Plant diagram *Pressure volume diagram used to analyse engines *Pourbaix diagram *Process flow diagram or PFD – used in chemical engineering *Program structure diagram ;R *Radar chart *Radial diagram *Requirement diagram Used in SysML *Rich picture *Randolph diagram, R-diagram *Routing diagram ;S *Sankey diagram – represents material, energy or cost flows with quantity proportional arrows in a process network *Sentence diagram – represents the grammar, grammatical structure of a natural language sentence *Sequence diagram from Unified Modeling Language, UML 8/9 and SysML *Specification and Design Language, SDL/GR diagram – specification and description Language. SDL is a formal language used in computer science. *Smith chart *Radar chart, Spider chart *Spray diagram *SSADM – structured systems analysis and design methodology (used in software engineering) *Star chart/Celestial sphere *State diagram are used for state machines in software engineering from Unified Modeling Language, UML 7/9 *Swim lane *Syntax diagram used in software engineering to represent a context-free grammar *Systems Biology Graphical Notation – a graphical notation used in diagrams of biochemical and cellular processes studied in systems biology *System context diagram *System structure *Systematic layout planning ;T *Timing diagram: digital timing diagram *Timing diagram: Unified Modeling Language, UML 2.0 *TQM Diagram *Tree structure *Treemapping, Treemap ;U *Unified Modeling Language#Diagrams, UML diagram – Unified Modeling Language (used in software engineering) *Use case, Use case diagram – from Unified Modeling Language, 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