semiautomaton homomorphism
Just like groups and rings, a semiautomaton can be viewed as an algebraic structure. As such, one may define algebraic constructs such as subalgebras and homomorphisms. In this entry, we will briefly discuss the later.
Definition
A homomorphism from a semiautomaton to a semiautomaton is a pair of maps such that
The image of the homomorphism is the subsemiautomaton of , where is the restriction of to , also known as the homomorphic image of under .
In general, a semiautomaton is said to be a homomorphic image of a semiautomaton , if there is a homomorphism such that .
When comparing two semiautomata , it is customary to identify the two corresponding input alphabets , especially when one wants to study the interaction between the states of and the states of . This can be done by taking , and extend the corresponding transition functions so that they are identities on the extended portions of the input alphabets. Call the extended semiautomata .
If is a homomorphism, then extends in a natural way: , and given by if , and if . Routine verification shows that is indeed a homomorphism: if ,
and if , then
A homomorphism is an isomorphism if both and are bijections. As discussed above, if we identify the input alphabets of and , and treat as the identity map on the input alphabet, then and are isomorphic if there is a bijection such that .
Specializations to Other Machines
Computing devices derived from semiautomata such as automata and state-output machines may also be considered as algebras. We record the definitions of homomorphisms with respect to these objects here.
We adopt the following notations: given an automaton and a state-output machine , let and be the associated semiautomaton . So and may be written and respectively.
Definition (automaton). Given automata and . Then
is a homomorphism if
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•
is a semiautomaton homomorphism, such that
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, and .
A homomorphism is an isomorphism if is an isomorphism such that and .
Definition (state-output machine). Given state-output machines and . Then
is a homomorphism if
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•
is a semiautomaton homomorphism, and
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•
, such that
for all , where and are the state and input alphabets of .
A homomorphism is an isomorphism if is an isomorphism and is a bijection.
References
- 1 A. Ginzburg, Algebraic Theory of Automata, Academic Press (1968).
Title | semiautomaton homomorphism |
Canonical name | SemiautomatonHomomorphism |
Date of creation | 2013-03-22 19:01:07 |
Last modified on | 2013-03-22 19:01:07 |
Owner | CWoo (3771) |
Last modified by | CWoo (3771) |
Numerical id | 7 |
Author | CWoo (3771) |
Entry type | Definition |
Classification | msc 68Q45 |
Classification | msc 20M35 |
Classification | msc 03D05 |
Classification | msc 68Q70 |
Defines | homomorphism |
Defines | homomorphic image |
Defines | isomorphism |
Defines | automaton homomorphism |
Defines | machine homomorphism |