Engineering is the science, skill, and profession of acquiring and applying scientific, economic, social, and practical knowledge, in order to design and also build structures, machines, devices, systems, materials and processes.
The American Engineers' Council for Professional Development (ECPD, the predecessor of ABET) has defined "engineering" as:
The creative application of scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behavior under specific operating conditions; all as respects an intended function, economics of operation or safety to life and property.
One who practices engineering is called an engineer, and those licensed to do so may have more formal designations such as Professional Engineer, Chartered Engineer, Incorporated Engineer, Ingenieur or European Engineer. The broad discipline of engineering encompasses a range of more specialized sub disciplines, each with a more specific emphasis on certain fields of application and particular areas of technology.
- 1 History
- 2 Main branches of engineering
- 3 Methodology
- 4 Social context
- 5 Relationships with other disciplines
- 6 See also
- 7 References
- 8 Further reading
- 9 External links
Engineering has existed since ancient times as humans devised fundamental inventions such as the pulley, lever, and wheel. Each of these inventions is consistent with the modern definition of engineering, exploiting basic mechanical principles to develop useful tools and objects.
The term engineering itself has a much more recent etymology, deriving from the word engineer, which itself dates back to 1325, when an engine'er (literally, one who operates an engine) originally referred to "a constructor of military engines." In this context, now obsolete, an "engine" referred to a military machine, i.e., a mechanical contraption used in war (for example, a catapult). Notable exceptions of the obsolete usage which have survived to the present day are military engineering corps, e.g., the U.S. Army Corps of Engineers.
Later, as the design of civilian structures such as bridges and buildings matured as a technical discipline, the term civil engineering entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline of military engineering.
The Pharos of Alexandria, the pyramids in Egypt, the Hanging Gardens of Babylon, the Acropolis and the Parthenon in Greece, the Roman aqueducts, Via Appia and the Colosseum, Teotihuacán and the cities and pyramids of the Mayan, Inca and Aztec Empires, the Great Wall of China, the Brihadeshwara temple of Tanjavur and tombs of India, among many others, stand as a testament to the ingenuity and skill of the ancient civil and military engineers.
The earliest civil engineer known by name is Imhotep. As one of the officials of the Pharaoh, Djosèr, he probably designed and supervised the construction of the Pyramid of Djoser (the Step Pyramid) at Saqqara in Egypt around 2630-2611 BC. He may also have been responsible for the first known use of columns in architecture[cn].
Ancient Greece developed machines in both the civilian and military domains. The Antikythera mechanism, the first known mechanical computer, and the mechanical inventions of Archimedes are examples of early mechanical engineering. Some of Archimedes' inventions as well as the Antikythera mechanism required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory that helped design the gear trains of the Industrial revolution, and are still widely used today in diverse fields such as robotics and automotive engineering.
Chinese, Greek and Roman armies employed complex military machines and inventions such as artillery which was developed by the Greeks around the 4th century B.C., the trireme, the ballista and the catapult. In the Middle Ages, the Trebuchet was developed.
The first steam engine was built in 1698 by mechanical engineer Thomas Savery. The development of this device gave rise to the industrial revolution in the coming decades, allowing for the beginnings of mass production.
With the rise of engineering as a profession in the eighteenth century, the term became more narrowly applied to fields in which mathematics and science were applied to these ends. Similarly, in addition to military and civil engineering the fields then known as the mechanic arts became incorporated into engineering.
Electrical engineering can trace its origins in the experiments of Alessandro Volta in the 1800s, the experiments of Michael Faraday, Georg Ohm and others and the invention of the electric motor in 1872. The work of James Maxwell and Heinrich Hertz in the late 19th century gave rise to the field of Electronics. The later inventions of the vacuum tube and the transistor further accelerated the development of electronics to such an extent that electrical and electronics engineers currently outnumber their colleagues of any other Engineering specialty.
The inventions of Thomas Savery and the Scottish engineer James Watt gave rise to modern Mechanical Engineering. The development of specialized machines and their maintenance tools during the industrial revolution led to the rapid growth of Mechanical Engineering both in its birthplace Britain and abroad.
Chemical Engineering, like its counterpart Mechanical Engineering, developed in the nineteenth century during the Industrial Revolution. Industrial scale manufacturing demanded new materials and new processes and by 1880 the need for large scale production of chemicals was such that a new industry was created, dedicated to the development and large scale manufacturing of chemicals in new industrial plants. The role of the chemical engineer was the design of these chemical plants and processes.
Aeronautical Engineering deals with aircraft design while Aerospace Engineering is a more modern term that expands the reach envelope of the discipline by including spacecraft design. Its origins can be traced back to the aviation pioneers around the turn of the century from the 19th century to the 20th although the work of Sir George Cayley has recently been dated as being from the last decade of the 18th century. Early knowledge of aeronautical engineering was largely empirical with some concepts and skills imported from other branches of engineering.
The first PhD in engineering (technically, applied science and engineering) awarded in the United States went to Willard Gibbs at Yale University in 1863; it was also the second PhD awarded in science in the U.S.
Only a decade after the successful flights by the Wright brothers, there was extensive development of aeronautical engineering through development of military aircraft that were used in World War I . Meanwhile, research to provide fundamental background science continued by combining theoretical physics with experiments.
Main branches of engineering
Engineering, much like other science, is a broad discipline which is often broken down into several sub-disciplines. These disciplines concern themselves with differing areas of engineering work. Although initially an engineer will usually be trained in a specific discipline, throughout an engineer's career the engineer may become multi-disciplined, having worked in several of the outlined areas. Engineering is often characterized as having four main branches:
- Chemical engineering – The application of physics, chemistry, biology, and engineering principles in order to carry out chemical processes on a commercial scale.
- Civil engineering – The design and construction of public and private works, such as infrastructure (airports, roads, railways, water supply and treatment etc.), bridges, dams, and buildings.
- Electrical engineering – The design and study of various electrical and electronic systems, such as electrical circuits, generators, motors, electromagnetic/electromechanical devices, electronic devices, electronic circuits, optical fibers, optoelectronic devices, computer systems, telecommunications, instrumentation, controls, and electronics.
- Mechanical engineering – The design of physical or mechanical systems, such as power and energy systems, aerospace/aircraft products, weapon systems, transportation products engines, compressors, powertrains, kinematic chains, vacuum technology, and vibration isolation equipment.
Beyond these four, sources vary on other main branches. Historically, naval engineering and mining engineering were major branches. Modern fields sometimes included as major branches include aerospace, petroleum, systems, audio engineering, architectural, biosystems, biomedical, industrial, materials science and nuclear engineering.[cn]
New specialties sometimes combine with the traditional fields and form new branches. A new or emerging area of application will commonly be defined temporarily as a permutation or subset of existing disciplines; there is often gray area as to when a given sub-field becomes large and/or prominent enough to warrant classification as a new "branch." One key indicator of such emergence is when major universities start establishing departments and programs in the new field.
For each of these fields there exists considerable overlap, especially in the areas of the application of sciences to their disciplines such as physics, chemistry and mathematics.
Engineers apply the sciences of physics and mathematics to find suitable solutions to problems or to make improvements to the status quo. More than ever, engineers are now required to have knowledge of relevant sciences for their design projects. As a result, they may keep on learning new material throughout their career.
If multiple options exist, engineers weigh different design choices on their merits and choose the solution that best matches the requirements. The crucial and unique task of the engineer is to identify, understand, and interpret the constraints on a design in order to produce a successful result. It is usually not enough to build a technically successful product; it must also meet further requirements.
Constraints may include available resources, physical, imaginative or technical limitations, flexibility for future modifications and additions, and other factors, such as requirements for cost, safety, marketability, productibility, and serviceability. By understanding the constraints, engineers derive specifications for the limits within which a viable object or system may be produced and operated.
Engineers use their knowledge of science, mathematics, logic, economics, and appropriate experience or tacit knowledge to find suitable solutions to a problem. Creating an appropriate mathematical model of a problem allows them to analyze it (sometimes definitively), and to test potential solutions.
Usually multiple reasonable solutions exist, so engineers must evaluate the different design choices on their merits and choose the solution that best meets their requirements. Genrich Altshuller, after gathering statistics on a large number of patents, suggested that compromises are at the heart of "low-level" engineering designs, while at a higher level the best design is one which eliminates the core contradiction causing the problem.
Engineers typically attempt to predict how well their designs will perform to their specifications prior to full-scale production. They use, among other things: prototypes, scale models, simulations, destructive tests, nondestructive tests, and stress tests. Testing ensures that products will perform as expected.
Engineers take on the responsibility of producing designs that will perform as well as expected and will not cause unintended harm to the public at large. Engineers typically include a factor of safety in their designs to reduce the risk of unexpected failure. However, the greater the safety factor, the less efficient the design may be.
The study of failed products is known as forensic engineering, and can help the product designer in evaluating his or her design in the light of real conditions. The discipline is of greatest value after disasters, such as bridge collapses, when careful analysis is needed to establish the cause or causes of the failure.
As with all modern scientific and technological endeavors, computers and software play an increasingly important role. As well as the typical business application software there are a number of computer aided applications (Computer-aided technologies) specifically for engineering. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods.
One of the most widely used tools in the profession is computer-aided design (CAD) software which enables engineers to create 3D models, 2D drawings, and schematics of their designs. CAD together with Digital mockup (DMU) and CAE software such as finite element method analysis or analytic element method allows engineers to create models of designs that can be analyzed without having to make expensive and time-consuming physical prototypes.
These allow products and components to be checked for flaws; assess fit and assembly; study ergonomics; and to analyze static and dynamic characteristics of systems such as stresses, temperatures, electromagnetic emissions, electrical currents and voltages, digital logic levels, fluid flows, and kinematics. Access and distribution of all this information is generally organized with the use of Product Data Management software.
There are also many tools to support specific engineering tasks such as Computer-aided manufacture (CAM) software to generate CNC machining instructions; Manufacturing Process Management software for production engineering; EDA for printed circuit board (PCB) and circuit schematics for electronic engineers; MRO applications for maintenance management; and AEC software for civil engineering.
- Original research is welcome on Wikinfo
Engineering is a subject that ranges from large collaborations to small individual projects. Almost all engineering projects are beholden to some sort of financing agency: a company, a set of investors, or a government. The few types of engineering that are minimally constrained by such issues are pro bono engineering and open design engineering.
By its very nature engineering is bound up with society and human behavior. Every product or construction used by modern society will have been influenced by engineering design. Engineering design is a very powerful tool to make changes to environment, society and economies, and its application brings with it a great responsibility. Many engineering societies have established codes of practice and codes of ethics to guide members and inform the public at large.
Engineering projects can be subject to controversy. Examples from different engineering disciplines include the development of nuclear weapons, the Three Gorges Dam, the design and use of Sport utility vehicles and the extraction of oil. In response, some western engineering companies have enacted serious corporate and social responsibility policies.
Engineering is a key driver of human development. Sub-Saharan Africa in particular has a very small engineering capacity which results in many African nations being unable to develop crucial infrastructure without outside aid. The attainment of many of the Millennium Development Goals requires the achievement of sufficient engineering capacity to develop infrastructure and sustainable technological development.
All overseas development and relief NGOs make considerable use of engineers to apply solutions in disaster and development scenarios. A number of charitable organizations aim to use engineering directly for the good of mankind:
- Engineers Without Borders
- Engineers Against Poverty
- Registered Engineers for Disaster Relief
- Engineers for a Sustainable World
- Engineering for Change
- Engineering Ministries International
Relationships with other disciplines
Scientists study the world as it is; engineers create the world that has never been.
There exists an overlap between the sciences and engineering practice; in engineering, one applies science. Both areas of endeavor rely on accurate observation of materials and phenomena. Both use mathematics and classification criteria to analyze and communicate observations.
Scientists may also have to complete engineering tasks, such as designing experimental apparatus or building prototypes. Conversely, in the process of developing technology engineers sometimes find themselves exploring new phenomena, thus becoming, for the moment, scientists.
In the book What Engineers Know and How They Know It, Walter Vincenti asserts that engineering research has a character different from that of scientific research. First, it often deals with areas in which the basic physics and/or chemistry are well understood, but the problems themselves are too complex to solve in an exact manner.
Examples are the use of numerical approximations to the Navier-Stokes equations to describe aerodynamic flow over an aircraft, or the use of Miner's rule to calculate fatigue damage. Second, engineering research employs many semi-empirical methods that are foreign to pure scientific research, one example being the method of parameter variation[cn].
As stated by Fung et al. in the revision to the classic engineering text, Foundations of Solid Mechanics:
"Engineering is quite different from science. Scientists try to understand
nature. Engineers try to make things that do not exist in nature. Engineers stress invention. To embody an invention the engineer must put his idea in concrete terms, and design something that people can use. That something can be a device, a gadget, a material, a method, a computing program, an innovative experiment, a new solution to a problem, or an improvement on what is existing. Since a design has to be concrete, it must have its geometry, dimensions, and characteristic numbers. Almost all engineers working on new designs find that they do not have all the needed information. Most often, they are limited by insufficient scientific knowledge. Thus they study mathematics, physics, chemistry, biology and mechanics. Often they have to add to the sciences relevant to their profession. Thus engineering sciencesare born."
Although engineering solutions make use of scientific principles, engineers must also take into account safety, efficiency, economy, reliability and constructability or ease of fabrication, as well as legal considerations such as patent infringement or liability in the case of failure of the solution.
Medicine and biology
The study of the human body, albeit from different directions and for different purposes, is an important common link between medicine and some engineering disciplines. Medicine aims to sustain, enhance and even replace functions of the human body, if necessary, through the use of technology.
Modern medicine can replace several of the body's functions through the use of artificial organs and can significantly alter the function of the human body through artificial devices such as, for example, brain implants and pacemakers. The fields of Bionics and medical Bionics are dedicated to the study of synthetic implants pertaining to natural systems.
Conversely, some engineering disciplines view the human body as a biological machine worth studying, and are dedicated to emulating many of its functions by replacing biology with technology. This has led to fields such as artificial intelligence, neural networks, fuzzy logic, and robotics. There are also substantial interdisciplinary interactions between engineering and medicine.
Both fields provide solutions to real world problems. This often requires moving forward before phenomena are completely understood in a more rigorous scientific sense and therefore experimentation and empirical knowledge is an integral part of both.
Medicine, in part, studies the function of the human body. The human body, as a biological machine, has many functions that can be modeled using Engineering methods.
The heart for example functions much like a pump, the skeleton is like a linked structure with levers, the brain produces electrical signals etc. These similarities as well as the increasing importance and application of Engineering principles in Medicine, led to the development of the field of biomedical engineering that uses concepts developed in both disciplines.
Newly emerging branches of science, such as Systems biology, are adapting analytical tools traditionally used for engineering, such as systems modeling and computational analysis, to the description of biological systems.
There are connections between engineering and art; they are direct in some fields, for example, architecture, landscape architecture and industrial design (even to the extent that these disciplines may sometimes be included in a University's Faculty of Engineering); and indirect in others.
The Art Institute of Chicago, for instance, held an exhibition about the art of NASA's aerospace design. Robert Maillart's bridge design is perceived by some to have been deliberately artistic. At the University of South Florida, an engineering professor, through a grant with the National Science Foundation, has developed a course that connects art and engineering.
In Political science the term engineering has been borrowed for the study of the subjects of Social engineering and Political engineering, which deal with forming political and social structures using engineering methodology coupled with political science principles. Financial engineering has similarly borrowed the term.
- ABET History
- Engineers' Council for Professional Development. (1947). Canons of ethics for engineers
- Engineers' Council for Professional Development definition on Encyclopaedia Britannica (Includes Britannica article on Engineering)
- Oxford English Dictionary
- Origin: 1250–1300; ME engin < AF, OF < L ingenium nature, innate quality, esp. mental power, hence a clever invention, equiv. to in- + -genium, equiv. to gen- begetting; Source: Random House Unabridged Dictionary, Random House, Inc. 2006.
- Barry J. Kemp, Ancient Egypt, Routledge 2005, p. 159
- "The Antikythera Mechanism Research Project", The Antikythera Mechanism Research Project. Retrieved 2007-07-01 Quote: "The Antikythera Mechanism is now understood to be dedicated to astronomical phenomena and operates as a complex mechanical "computer" which tracks the cycles of the Solar System."
- Wilford, John. (July 31, 2008). Discovering How Greeks Computed in 100 B.C.. New York Times.
- Wright, M T. (2005). "Epicyclic Gearing and the Antikythera Mechanism, part 2". Antiquarian Horology 29 (1 (September 2005)): 54–60.
- Britannica on Greek civilization in the 5th century Military technology Quote: "The 7th century, by contrast, had witnessed rapid innovations, such as the introduction of the hoplite and the trireme, which still were the basic instruments of war in the 5th." and "But it was the development of artillery that opened an epoch, and this invention did not predate the 4th century. It was first heard of in the context of Sicilian warfare against Carthage in the time of Dionysius I of Syracuse."
- Merriam-Webster Collegiate Dictionary, 2000, CD-ROM, version 2.5.
- Jenkins, Rhys (1936). Links in the History of Engineering and Technology from Tudor Times. Ayer Publishing. p. 66. ISBN 0-8369-2167-4.
- Imperial College: Studying engineering at Imperial: Engineering courses are offered in five main branches of engineering: aeronautical, chemical, civil, electrical and mechanical. There are also courses in computing science, software engineering, information systems engineering, materials science and engineering, mining engineering and petroleum engineering.
- Van Every, Kermit E. (1986). "Aeronautical engineering". Encyclopedia Americana. 1. Grolier Incorporated. pp. 226.
- Wheeler, Lynde, Phelps (1951). Josiah Willard Gibbs — the History of a Great Mind. Ox Bow Press. ISBN 1-881987-11-6.
- Journal of the British Nuclear Energy Society: Volume 1 British Nuclear Energy Society - 1962 - Snippet view Quote: In most universities it should be possible to cover the main branches of engineering, ie civil, mechanical, electrical and chemical engineering in this way. More specialised fields of engineering application, of which nuclear power is ...
- The Engineering Profession by Sir James Hamilton, UK Engineering Council Quote: "The Civilingenior degree encompasses the main branches of engineering civil, mechanical, electrical, chemical." (From the Internet Archive)
- Bronzino JD, ed., The Biomedical Engineering Handbook, CRC Press, 2006, ISBN 0-8493-2121-2
- Arbe, Katrina (2001.05.07). "PDM: Not Just for the Big Boys Anymore". ThomasNet. http://news.thomasnet.com/IMT/archives/2001/05/pdm_not_just_fo.html.
- Arbe, Katrina (2003.05.22). "The Latest Chapter in CAD Software Evaluation". ThomasNet. http://news.thomasnet.com/IMT/archives/2003/05/the_latest_chap.html.
- PDF on Human Development
- MDG info pdf
- Home page for EMI
- Rosakis, Ares Chair, Division of Engineering and Applied Science. "Chair's Message, CalTech.". http://www.eas.caltech.edu/about/chair. Retrieved 15 October 2011.
- Ryschkewitsch, M.G. NASA Chief Engineer. "Improving the capability to Engineer Complex Systems –Broadening the Conversation on the Art and Science of Systems Engineering". p. 8. http://sdm.mit.edu/conf09/presentations/ryschkewitsch.pdf. Retrieved 15 October 2011.
- American Society for Engineering Education (1970). Engineering education. 60. American Society for Engineering Education. p. 467. http://books.google.ca/books?id=frZVAAAAMAAJ&q=Scientists+study+the+world+as+it+is;+engineers+create+the+world+that+has+never+been&dq=Scientists+study+the+world+as+it+is;+engineers+create+the+world+that+has+never+been&hl=en&ei=v7OZTrXBL6Lx0gGpu5TgBA&sa=X&oi=book_result&ct=result&resnum=6&ved=0CEQQ6AEwBQ. "The great engineer Theodore von Karman once said, "Scientists study the world as it is, engineers create the world that never has been." Today, more than ever, the engineer must create a world that never has been..."
- Vincenti, Walter G. (1993). What Engineers Know and How They Know It: Analytical Studies from Aeronautical History. Johns Hopkins University Press. ISBN 0-8018-3974-2.
- Classical and Computational Solid Mechanics, YC Fung and P. Tong. World Scientific. 2001.
- Bjerklie, David. "The Art of Renaissance Engineering." MIT's Technology Review Jan./Feb.1998: 54-9. Article explores the concept of the "artist-engineer", an individual who used his artistic talent in engineering. Quote from article: Da Vinci reached the pinnacle of "artist-engineer"-dom, Quote2: "It was Leonardo da Vinci who initiated the most ambitious expansion in the role of artist-engineer, progressing from astute observer to inventor to theoretician." (Bjerklie 58)
- Ethical Assessment of Implantable Brain Chips. Ellen M. McGee and G. Q. Maguire, Jr. from Boston University
- IEEE technical paper: Foreign parts (electronic body implants).by Evans-Pughe, C. quote from summary: Feeling threatened by cyborgs?
- Institute of Medicine and Engineering: Mission statement The mission of the Institute for Medicine and Engineering (IME) is to stimulate fundamental research at the interface between biomedicine and engineering/physical/computational sciences leading to innovative applications in biomedical research and clinical practice.
- IEEE Engineering in Medicine and Biology: Both general and technical articles on current technologies and methods used in biomedical and clinical engineering...
- Royal Academy of Engineering and Academy of Medical Sciences: Systems Biology: a vision for engineering and medicine in pdf: quote1: Systems Biology is an emerging methodology that has yet to be defined quote2: It applies the concepts of systems engineering to the study of complex biological systems through iteration between computational and/or mathematical modelling and experimentation.
- Science Museum of Minnesota: Online Lesson 5a; The heart as a pump
- Minnesota State University emuseum: Bones act as levers
- UC Berkeley News: UC researchers create model of brain's electrical storm during a seizure
- Lehigh University project: We wanted to use this project to demonstrate the relationship between art and architecture and engineering
- National Science Foundation:The Art of Engineering: Professor uses the fine arts to broaden students' engineering perspectives
- MIT World:The Art of Engineering: Inventor James Dyson on the Art of Engineering: quote: A member of the British Design Council, James Dyson has been designing products since graduating from the Royal College of Art in 1970.
- University of Texas at Dallas: The Institute for Interactive Arts and Engineering
- Aerospace Design: The Art of Engineering from NASA’s Aeronautical Research
- Princeton U: Robert Maillart's Bridges: The Art of Engineering: quote: no doubt that Maillart was fully conscious of the aesthetic implications...
- quote:..the tools of artists and the perspective of engineers..
- Drew U: user website: cites Bjerklie paper
- Dorf, Richard, ed. (2005). The Engineering Handbook (2 ed.). Boca Raton: CRC. ISBN 0-8493-1586-7.
- Billington, David P. (1996-06-05). The Innovators: The Engineering Pioneers Who Made America Modern. Wiley; New Ed edition. ISBN 0-471-14026-0.
- Petroski, Henry (1992-03-31). To Engineer is Human: The Role of Failure in Successful Design. Vintage. ISBN 0-679-73416-3.
- Petroski, Henry (1994-02-01). The Evolution of Useful Things: How Everyday Artifacts-From Forks and Pins to Paper Clips and Zippers-Came to be as They are. Vintage. ISBN 0-679-74039-2.
- Lord, Charles R. (2000-08-15). Guide to Information Sources in Engineering. Libraries Unlimited. doi:10.1336/1563086999. ISBN 1-56308-699-9.
- Vincenti, Walter G. (1993-02-01). What Engineers Know and How They Know It: Analytical Studies from Aeronautical History. The Johns Hopkins University Press. ISBN 0-8018-4588-2.
- Hill, Donald R. (1973-12-31) . The Book of Knowledge of Ingenious Mechanical Devices: Kitáb fí ma'rifat al-hiyal al-handasiyya. Pakistan Hijara Council. ISBN 969-8016-25-2.
|40x40px||Look up engineering in Wiktionary, the free dictionary.|
|40x40px||Wikiversity has learning materials about Engineering|
|40x40px||Wikiquote has a collection of quotations related to: Engineering|
- National Society of Professional Engineers position statement on Licensure and Qualifications for Practice
- National Academy of Engineering (NAE)
- American Society for Engineering Education (ASEE)
- The US Library of Congress Engineering in History bibliography
- ICES: Institute for Complex Engineered Systems, Carnegie Mellon University, Pittsburgh, PA
- History of engineering bibliography at University of Minnesota
|This page uses content from Wikipedia. The original article was at Engineering.
The list of authors can be seen in the page history. The text of this Wikinfo article is available under the GNU Free Documentation License and the Creative Commons Attribution-Share Alike 3.0 license.