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<div>An '''artificial chemistry''' is a [[computer model]] used to simulate various types of [[system]]s. Artificial chemistry is in some ways similar to a chemical reaction, hence the name. The field of artificial chemistry originated in [[artificial life]] but has shown to be a versatile method with applications in many fields such as [[chemistry]], [[economics]], [[sociology]] and [[linguistics]].<br />
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==Formal definition==<br />
An artificial chemistry is defined in general as a triple (S,R,A). In some cases it is sufficient to define it as a tuple (S,I).<br />
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*S is the [[Set (mathematics)|set]] of possible molecules S={s<sub>1</sub>...,s<sub>n</sub>}, where n is the number of elements in the set, possibly infinite. <br />
*R is a set of [[arity|n-ary]] [[operation (mathematics)|operation]]s on the molecules in S, the reaction rules R={r<sub>1</sub>...,r<sub>n</sub>}. Each rule r<sub>i</sub> is written like a chemical reaction a+b+c->a*+b*+c*. Note here that r<sub>i</sub> are operators, as opposed to +.<br />
*A is an [[algorithm]] describing how to apply the rules R to a [[subset]] P<math>\subset</math>S.<br />
*I are the interaction rules of the molecules in S.<br />
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==Types of artificial chemistries==<br />
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* depending on the space of possible molecules<br />
** finite<br />
** infinite<br />
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* depending on the type of reactions<br />
** catalytic systems<br />
** reactive systems<br />
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* depending on the space topology<br />
** well stirred reactor<br />
** topologically arranged (1,2,3 dimensional)<br />
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==Important concepts==<br />
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* Organizations: An organization is a set of molecules that is closed and self-maintaining. As such, it is a set that does not create anything outside itself, and such that any molecule inside the set can be generated within the set.<br />
* Closed sets<br />
* Self-maintaining sets<br />
* Hasse diagram of organizations<br />
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==History of artificial chemistries==<br />
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Artificial chemistries emerged as a sub-field of [[artificial life]], in particular from [[strong artificial life]]. The idea behind this field was that if one wanted to build something alive, it had to be done by a combination of non-living entities. For instance, a cell is itself alive, and yet is a combination of non-living molecules. Artificial chemistry enlists, among others, researchers that believe in an extreme bottom-up approach to artificial life.<br />
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==Important contributors==<br />
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The first reference about artificial Chemistries come from a Technical paper written by [[John McCaskill]]. [[Walter Fontana]] working with [[Leo Buss]] then took up the work developing the [[AlChemy model]]. The model was presented at the second International Conference of Artificial Life. In his first papers he presented the concept of [[organization]], as a set of molecules that is algebraically closed and self-maintaining.<br />
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Two main schools of artificial chemistries have been in Japan and Germany. In Japan the main researchers have been [[Takashi Ikegami]], [[Hideaki Suzuki]] and [[Yasuhiro Suzuki]]. In [[Germany]], it was [[Wolfgang Banzhaf]], who, together with his students [[Peter Dittrich]] and [[Jens Ziegler]], developed various<br />
artificial chemistry models. Their 2001 paper 'Artificial Chemistries - A Review' became a standard in the field. [[Jens Ziegler]], as part of his PhD thesis, proved that an artificial chemistry could be used to control a small Khepera robot. Among other models, [[Peter Dittrich]] developed the [[Seceder model]] which is able to explain group formation in society through some simple rules. Since then he became a professor in [[Jena]] where he investigates artificial chemistries as a way to define a general theory of [[constructive dynamical system]]s.<br />
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==Applications of artificial chemistries==<br />
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Artificial Chemistries are often used in the study of protobiology, in trying to bridge the gap between [[chemistry]] and [[biology]].<br />
A further motivation to study artificial chemistries is the interest in constructive dynamical systems. [[Yasuhiro Suzuki]] has modeled various systems such as membrane systems, signaling pathways (P53), ecosystems, and enzyme systems by using his method, abstract rewriting system on multisets (ARMS).<br />
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==See also==<br />
*[[Cellular automaton|Cellular automata]]<br />
*[[Computational chemistry]] - the use of simplified models to simulate chemical interactions<br />
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==External links and references==<br />
*[http://web.cs.mun.ca/~banzhaf/papers/alchemistry_review_MIT.pdf Artificial chemistries—a review (PDF)]<br />
*[http://www.sq3.org.uk/wiki.pl?Papers Tim Hutton's Papers & Talks] - includes several papers on artificial chemistries for artificial life<br />
*[http://www.minet.uni-jena.de/~biosys/twiki/bin/view.pl/ACHEM/WebHome the ARTIFICIAL CHEMISTRY webpage] of [[Peter Dittrich]]'s workgroup.<br />
*[http://protobiology.org the protobiology.org website] <br />
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[[Category:Artificial life]]</div>162.93.80.2