Several international standards for asynchronous data compression are available today. In 1993 the International Telecommunication Union (ITU) started to research possible ways to compress synchronous data. Special at...
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Several international standards for asynchronous data compression are available today. In 1993 the International Telecommunication Union (ITU) started to research possible ways to compress synchronous data. Special attention was given to compatibility with previous asynchronous standards, namely V.42bis. In September 1993 a proposal for modification of the V.42bis standard to make ii applicable to synchronous data was published. In this paper a prototype of a synchronous data link layer protocol based on the ITU proposals is described. The protocol chosen is HDLC based. The V.42bis compression standard is adapted to serve the needs of a synchronous protocol. A functional model is designed followed by a performance analysis of the protocol. The analysis shows a decrease of the compression ratio due to the adaption of the compression algorithm. (C) 1997 Elsevier science B.V.
A Health Care Establishment (HCE) is an establishment where medical services are rendered. The above services are provided by the health care personnel. The infrastructure of a HCE may include Information Technology (...
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Security management is one of the key functional areas in open systems network management. Two key aspects of security management are managing user security services and providing security to network management system...
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Security management is one of the key functional areas in open systems network management. Two key aspects of security management are managing user security services and providing security to network management systems. These are examined in tum to give the reader an overview of the state-of-the-art in security management. The ISO OSI Reference Model is used as a basis to present the security threats, security services and mechanisms which have to be managed. Telecommunications management networks are used as an example of management applications which both provide management and require the provision of security and security management services. The OSI approach to network management is examined in detail. This is followed by a survey of the categories of OSI security management activities, and a discussion of the security management needs of various common security services. The need for security for network management systems is examined.
This paper presents the Secure Environment for Information systems in Medicine (SEISMED) project which is funded by the Commission of the European Commzlnities (CEC) under the Advance Informatics in Medicine (AIM) pro...
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It is known that two-way pushdown automata are more powerful than two-way counter machines. The result is also true for the case when the pushdown store and counter are reversal-bounded. In contrast, we show that two-...
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It is known that two-way pushdown automata are more powerful than two-way counter machines. The result is also true for the case when the pushdown store and counter are reversal-bounded. In contrast, we show that two-way reversal-bounded push-down automata over bounded languages (i.e., subsets of for some distinct symbols a 1 ,…, a k ) are equivalent to two-way reversal-bounded counter machines. We also show that, unlike the unbounded input case, two-way reversal-bounded pushdown automata over bounded languages have decidable emptiness, equivalence and containment problems.
作者：
JIANG, TDepartment of Computer Science and Systems
McMaster University Hamilton Ontario Canada L8S 4K1[∗]Research supported in part by a grant from SERB McMaster University and NSERC Operating Grant OGP 0046613.
The generalized firing squad synchronization problem (gfssp) is the well-known firing squad synchronization problem (fssp) extended to arbitrarily connected networks of finite automata. Here, the transmission delays a...
The generalized firing squad synchronization problem (gfssp) is the well-known firing squad synchronization problem (fssp) extended to arbitrarily connected networks of finite automata. Here, the transmission delays associated with the links of a network are assumed to be 0; i.e., a signal can get through a link in no time. When the delays are allowed to be arbitrary non❉ integers, the problem is called gfssp-nud (i.e., gfssp with nonuniform delays). We give for the first time a solution of gfssp-nud. The solution is independent of the structure of the network and the actual delays of the links. The firing time of the solution is bounded by O(Δ3+τmax), where τmax is the maximum transmission delay of any single link and Δ is the maximum transmission delay between the general and any other node of a given network. This answers an open question in Mazoyer (in “Automata Networks” (C. Choffrut, Ed.), pp. 82–93, Springer-Verlag, Berlin/New York, 1986). Our result is based on a strategy different from the one of Balzer and Waksman, which is used in almost all existing solutions of fssp and gfssp. The extension of gfssp and gfssp-nud to networks with more than one general is also considered. We show that (1) for any fixed k≥2, gfssp with at most k generals has a solution whose firing time is bounded by O(D), where D is the maximum distance between any two nodes of a given network, and gfssp-nud with at most k generals has a solution whose firing time is bounded by O((Φ+τmax)3), where Φ is the maximum transmission delay between any two nodes of a given network; (2) there are no solutions for gfssp and gfssp-nud with an arbitrary number of generals.
Many difficult open problems in theoretical computerscience center around non-determinism. We study the fundamental problem of converting a given deterministic finite automaton (DFA) to a minimal nondeterministic fin...
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Many difficult open problems in theoretical computerscience center around non-determinism. We study the fundamental problem of converting a given deterministic finite automaton (DFA) to a minimal nondeterministic finite automaton (NFA). Despite extensive work on finite automata, this fundamental problem has remained open. Recently, we studied this problem and showed that this (and related) problems are computationally hard . 11 Herewe study the restriction of this problem to the case when the input DFA is over a one-letter alphabet. Even in this restricted case the problem is computationally hard even though our evidence of hardness is different from (and is weaker than) the standard ones such as NP-hardness. Let A → B denote the problem of converting a finite automaton of type A to a minimal finite automaton of type B. Our main result is that DFA → NFA , when the input is a unary cyclic DFA (a DFA whose graph is a simple cycle), is in NP but not in P unless NP ⊆ DTIME (n O( log n) ). Our work was also motivated by the problem of finding structurally simple “normal forms” of NFA’s over a unary alphabet. We present some normal forms for minimal NFA’s over a unary alphabet and present an application to lower bounds on the size complexity of an NFA. In fact, the normal form result is used in a nontrivial manner to show the NP membership result stated above.
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