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Composability of infinite-state activity automata
, 2004
"... Abstract. Let be a class of (possibly nondeterministic) language acceptors with a oneway input tape. A system of automata in, is composable if for every string of symbols accepted by, there is an assignment of each symbol in to one of the ’s such that if is the subsequence assigned to, then is accep ..."
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Abstract. Let be a class of (possibly nondeterministic) language acceptors with a oneway input tape. A system of automata in, is composable if for every string of symbols accepted by, there is an assignment of each symbol in to one of the ’s such that if is the subsequence assigned to, then is accepted by. For a nonnegative integer, a-lookahead delegator for is a deterministic machine in which, knowing (a) the current states! of and the accessible “local ” information of each machine (e.g., the top of the stack if each machine is a pushdown automaton, whether a counter is zero on nonzero if each machine is a multicounter automaton, etc.), and (b) the lookahead symbols to the right of the current input symbol being processed, can uniquely determine " the to assign the current symbol. Moreover, every string accepted by is also accepted by, i.e., the subsequence of string delegated by to " each is accepted by. Thus,-lookahead delegation is a stronger requirement than composability, since the delegator must be deterministic. A system that is composable may not have a-delegator for any. We look at the decidability of composability and existence of-delegators for various classes of machines. Our results have applications to automated composition of e-services. E-
Real-counter automata and their decision problems
- in: FSTTCS, LNCS 3328
"... Abstract. We introduce real-counter automata, which are two-way finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, real-counter automata accept real words that are bounded and closed real intervals delimited by a ..."
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Abstract. We introduce real-counter automata, which are two-way finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, real-counter automata accept real words that are bounded and closed real intervals delimited by a finite number of markers. We study the membership and emptiness problems for one-way/twoway real-counter automata as well as those automata further augmented with other unbounded storage devices such as integer-counters and pushdown stacks. 1
Real-Counter Automata and Verification ⋆ (Extended Abstract)
"... Abstract. We introduce real-counter automata, which are two-way finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, real-counter automata accept real words that are bounded and closed real intervals delimited by a ..."
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Abstract. We introduce real-counter automata, which are two-way finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, real-counter automata accept real words that are bounded and closed real intervals delimited by a finite number of markers. We study the membership and emptiness problems for one-way/twoway real-counter automata as well as those automata further augmented with other unbounded storage devices such as integer-counters and pushdown stacks. 1
Abstract On Composition and Lookahead Delegation of-Services Modeled by Automata ¡£ ¢ ¡¤¡
"... Let � be a class of (possibly nondeterministic) language acceptors with a one-way input tape. A system ������������������������ � of automata in � is composable if for every string ��� � ������ � �� � of symbols accepted by � , there is an assignment of each symbol �� � in � to one of the �� � ’s su ..."
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Let � be a class of (possibly nondeterministic) language acceptors with a one-way input tape. A system ������������������������ � of automata in � is composable if for every string ��� � ������ � �� � of symbols accepted by � , there is an assignment of each symbol �� � in � to one of the �� � ’s such that for each �����£�� � , the subsequence of � assigned to �� � is accepted by � �. For a nonnegative integer � , a �-lookahead delegator for ������ � � ���������� � � � is a deterministic machine � in � which, knowing (a) the current states of ���� � � ���������� � � and the accessible “local ” information of each machine (e.g., the top of the stack if each machine is a pushdown automaton, whether a counter is zero or nonzero if each machine is a multicounter automaton, etc.), and (b) the � lookahead symbols to the right of the current input symbol being processed, can uniquely determine the � � to assign the current symbol. Moreover, every string � accepted by � is also accepted by � ; i.e., the subsequence of string � delegated by � to each � � is accepted by � �. Thus, �-lookahead delegation is a stronger requirement than composability, since the delegator � must be deterministic. A system that is composable may not have a �-delegator for any �. We study the decidability of composability and existence of �-delegators for various