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Composability of infinitestate 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, alookahead 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 adelegator for any. We look at the decidability of composability and existence ofdelegators for various classes of machines. Our results have applications to automated composition of eservices. E
Realcounter automata and their decision problems
 in: FSTTCS, LNCS 3328
"... Abstract. We introduce realcounter automata, which are twoway finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, realcounter automata accept real words that are bounded and closed real intervals delimited by a ..."
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Abstract. We introduce realcounter automata, which are twoway finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, realcounter 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 oneway/twoway realcounter automata as well as those automata further augmented with other unbounded storage devices such as integercounters and pushdown stacks. 1
RealCounter Automata and Verification ⋆ (Extended Abstract)
"... Abstract. We introduce realcounter automata, which are twoway finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, realcounter automata accept real words that are bounded and closed real intervals delimited by a ..."
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Abstract. We introduce realcounter automata, which are twoway finite automata augmented with counters that take real values. In contrast to traditional word automata that accept sequences of symbols, realcounter 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 oneway/twoway realcounter automata as well as those automata further augmented with other unbounded storage devices such as integercounters and pushdown stacks. 1
Abstract On Composition and Lookahead Delegation ofServices Modeled by Automata ¡£ ¢ ¡¤¡
"... 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 su ..."
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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 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