It is a well-established fact that each regular expression can be transformed into a non-deterministic finite automaton (NFA) with or without ffl-transitions, and all authors seem to provide their own variant of the construction. Of these, Berry and Sethi [BS86] have shown that the construction of an ffl-free NFA due to to Glushkov [Glu61] is a natural representation of the regular expression, because it can be described in terms of the Brzozowski derivatives [Brz64] of the expression. Moreover, the Glushkov construction also plays a significant role in the document processing area: The SGML standard [ISO86], now widely adopted by publishing houses and government agencies for the syntactic specification of textual markup systems, uses deterministic regular expressions, i.e. expressions whose Glushkov automaton is deterministic, as a description language for document types. In this paper, we first show that the Glushkov automaton can be constructed in time quadratic in the size of the...

The Standard Generalized Markup Language (SGML) is an ISO standard that provides a syntactic meta-language for the definition of textual markup systems, which are used to indicate the structure of documents so that they can be electronically typeset, searched, and communicated. We address only one problem raised by the standard, namely: In SGML, the right-hand sides of context-free productions are regular expressions, called content models, that are restricted to be what the standard calls "unambiguous," but what is more appropriately called deterministic. We solve the problem of how to define determinism precisely, how to recognize deterministic regular expressions efficiently, and how to recognize deterministic regular languages. Any SGML parser must check that a given document grammar conforms to the standard; that is, it must validate it. Hence, our results are an important step in the clarification of the standard and in the efficient implementation of an SGML parser fo...

The ISO standard for Standard Generalized Markup Language (SGML) provides a syntactic meta-language for the definition of textual markup systems. In the standard the right hand sides of productions are called content models and they are based on regular expressions. The allowable regular expressions are those that are "unambiguous" as defined by the standard. Unfortunately, the standard's use of the term "unambiguous" does not correspond to the two well known notions, since not all regular languages are denoted by "unambiguous" expressions. Furthermore, the standard's definition of "unambiguous" is somewhat vague. Therefore, we provide a precise definition of "unambiguous expressions" and rename them deterministic regular expressions to avoid any confusion. A regular expression E is deterministic if the canonical ffl-free finite automaton ME recognizing L(E) is deterministic. A regular language is deterministic if there is a deterministic expression that denotes it. We gi...

Despite the almost universal reliance on testing as the means of locating software errors and its long history of use, few criteria have been proposed for deciding when software has been thoroughly tested. As a basis for the development of usable notions of test data adequacy, an abstract definition is proposed and examined, and approximations to this definition are considered.

Abstract — This paper presents a software architecture for the network-transparent control of distributed robotic systems. The system consists of two main components: a generic and easily extensible CORBA-based interface to distributed services, and a high-level XML-based description language for specifying the behavior of the robots. The architecture makes it possible to create dynamically modifiable, extensible control software with ease. It is successfully utilized in implementing a coffee serving system in which the co-operation of two very different robots and two other distributed services are needed. I.

resented that targets faults individually in two phases: fault activation and fault propagation. Genetically-engineered finite-state machine sequences are used to aid both the fault activation and fault-propagation phases. These finite-state machine sequences provide important information about state justification, as well as propagation of fault effects. Further refinements on state justification using dynamic state traversal are performed to improve the activation of the hard-to-activate faults. The size of a test set directly impacts the cost of testing. Long test sequences usually result when the hard faults are targeted. Thus, compaction of test sets is necessary to reduce the testing iii cost. Test set compaction, however, is an NP-complete problem in itself. Instead of an exhaustive search of the most compact test set, two fast algorithms for test set compaction are developed that reduce the test set sizes significantly at very low computational cost. Finally, synchronizing se

Abstract. A projection is a simplified system description or viewpoint that emphasises some of the system properties while hiding others. In this paper, we describe a projection transformation that, when applied to SDL components, produces semantic interface descriptions. Contrarily to traditional object interfaces that restrict to the declaration of operation signatures, semantic interfaces describe dialogues and constraints between components, and can be exploited in order to build a system that behaves correctly. Using projections simplifies the validation analysis, and enables the designer to comprehend single interfaces. When following this approach, ambiguous and conflicting behaviours can be identified already at design time. 1

Effective diagnosis of integrated circuits relies critically on the quality of diagnostic test vectors. Diagnostic test pattern generation aims at producing test vectors that distinguish between all distinguishable pairs of faults, and proving the remaining pairs of faults to be indistinguishable. Proving indistinguishabilities, much like proving undetectabilities in the case of detection-oriented test pattern generation, requires substantial computational effort. In this paper, we simplify the problem by showing that a significant number of indistinguishability relations can be proven implicitly, with little computational effort. Sequential indistinguishability is characterized and conditions for the identification of new indistinguishability relations based on already existing relations are established. Experiments on the ISCAS 89 benchmark circuits are presented to indicate the significant improvements achievable by the implicit identification of indistinguishabilities. 1 Introduct...

I. INTRODUCTION. The currently used technologies for design of digital circuits include, among others, gate arrays, standard cells, custom and semi-custom circuits and Programmable Logic Devices. Many design automation tools are currently available on the market for these technologies from di erent vendors. They include:

We introduce theorems that enable efficient identification of indistinguishable fault pairs in synchronous sequential circuits using an iterative logic array of limited length. These theorems can be used for identifying fault pairs that can be dropped from consideration before diagnostic ATPG starts, thus improving the efficiency of diagnostic ATPG. Experimental results are presented to demonstrate the effectiveness of the proposed theorems, which allow us to identify almost all the indistinguishable fault pairs in finite-state machine benchmarks.