Schema (genetic algorithms)
A schema is a template in computer science used in the field of genetic algorithms that identifies a subset of strings with similarities at certain string positions. Schemata are a special case of cylinder sets; and so form a topological space.[1]
Description
For example, consider binary strings of length 6. The schema 1**0*1 describes the set of all Words of length 6 with 1's at positions 1 and 6 and a 0 at position 4. The * is a wildcard symbol, which means that positions 2, 3 and 5 can have a value of either 1 or 0. The order of a schema is defined as the number of fixed positions in the template, while the defining length is the distance between the first and last specific positions. The order of 1**0*1 is 3 and its defining length is 5. The fitness of a schema is the average fitness of all strings matching the schema. The fitness of a string is a measure of the value of the encoded problem solution, as computed by a problem-specific evaluation function.
Length
The length of schema a depends on the total number of nodes in the schema and is called the length N(H) of a schema H. N(H) is also equal to the number of nodes in the programs matching H.[2]
Disruption
If the child of an individual that matches schema H does not itself match H, the schema is said to have been disrupted.[2]
See also
References
- ^ Holland (1992 reprint). Adaptation in Natural and Artificial Systems. The MIT Press.
{{cite book}}:|access-date=requires|url=(help); Check date values in:|year=(help); More than one of|author=and|last=specified (help)CS1 maint: year (link) - ^ a b "Foundations of Genetic Programming". UCL UK. Retrieved 13 July 2010.
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