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96
An Experiment in Specificationbased Testing
 IEEE TRANSACTIONS ON SOFTWARE ENGINEERING
, 1995
"... The Test Template Framework (TTF) is a formal, abstract model of tests used to derive a hierarchy of test information, including test cases and oracles. The hierarchy is derived from a formal modelbased specification, for example, one written in the Z notation. We present a case study deriving ..."
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Cited by 85 (8 self)
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The Test Template Framework (TTF) is a formal, abstract model of tests used to derive a hierarchy of test information, including test cases and oracles. The hierarchy is derived from a formal modelbased specification, for example, one written in the Z notation. We present a case study deriving a Test Template Hierarchy (TTH) from a specification for topological sorting. Test suites were also prepared from the same specification by two classes of testers: experts and nonexperts. Qualitative analysis of the test suites indicated a lack of structured process in their development. The suites were analysed quantitatively by executing all valid test inputs on five implementations seeded with faults and the TTFderived suite was the only one to identify all faults. The most structured of the nonTTF suites identified more faults than any other nonTTF suite, and it was found to be covered by the TTFderived suite. This informal comparison demonstrates that a systematic, formal ...
Theory and Algorithms for Plan Merging
, 1992
"... Merging operators in a plan can yield significant savings in the cost to execute a plan. This paper provides a formal theory for plan merging and presents both optimal and efficient heuristic algorithms for finding minimumcost merged plans. The optimal planmerging algorithm applies a dynamic progr ..."
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Cited by 69 (3 self)
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Merging operators in a plan can yield significant savings in the cost to execute a plan. This paper provides a formal theory for plan merging and presents both optimal and efficient heuristic algorithms for finding minimumcost merged plans. The optimal planmerging algorithm applies a dynamic programming method to handle multiple linear plans and is extended to partially ordered plans in a novel way. Furthermore, with worst and average case complexity analysis and empirical tests, we demonstrate that efficient and wellbehaved approximation algorithms are applicable for optimizing plans with large sizes.
Access Rights Administration in RoleBased Security Systems
 DATABASE SECURITY VIII: STATUS AND PROSPECTS
, 1994
"... This paper examines the concept of rolebased protection and, in particular, role organization. From basic role relationships, a model for role organization is developed. The role graph model, its operator semantics based on graph theory and algorithms for role administration are proposed. The ro ..."
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Cited by 60 (12 self)
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This paper examines the concept of rolebased protection and, in particular, role organization. From basic role relationships, a model for role organization is developed. The role graph model, its operator semantics based on graph theory and algorithms for role administration are proposed. The role graph model, in our view, presents a very generalized form of role organization for access rights administration. It is shown how the model simulates other organizational structures such as hierarchies [TDH92] and privilege graphs [Bal90].
A Linear Time Algorithm for Finding All Maximal Scoring Subsequences
 In Proceedings of the Seventh International Conference on Intelligent Systems for Molecular Biology
, 1999
"... Given a sequence of real numbers ("scores"), we present a practical linear time algorithm to find those nonoverlapping, contiguoussubsequenceshaving greatest total scores. This improves on the best previously known algorithm, which requires quadratic time in the worst case. The problem arises i ..."
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Cited by 44 (3 self)
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Given a sequence of real numbers ("scores"), we present a practical linear time algorithm to find those nonoverlapping, contiguoussubsequenceshaving greatest total scores. This improves on the best previously known algorithm, which requires quadratic time in the worst case. The problem arises in biological sequence analysis, where the highscoring subsequences correspond to regions of unusual composition in a nucleic acid or protein sequence. For instance, Altschul, Karlin, and others have used this approach to identify transmembrane regions, DNA binding domains, and regions of high charge in proteins. Keywords: maximal scoring subsequence, locally optimal subsequence, maximum sum interval, sequence analysis. 1 Introduction When analyzing long nucleic acid or protein sequences, the identification of unusual subsequences is an important task, since such features may be biologically significant. A common approach is to assign a score to each residue, and then look for contig...
Information flow decomposition for network coding
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 2006
"... We propose a method to identify structural properties of multicast network configurations, by decomposing networks into regions through which the same information flows. This decomposition allows us to show that very different networks are equivalent from a coding point of view, and offers a means t ..."
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Cited by 42 (10 self)
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We propose a method to identify structural properties of multicast network configurations, by decomposing networks into regions through which the same information flows. This decomposition allows us to show that very different networks are equivalent from a coding point of view, and offers a means to identify such equivalence classes. It also allows us to divide the network coding problem into two almost independent tasks: one of graph theory and the other of classical channel coding theory. This approach to network coding enables us to derive the smallest code alphabet size sufficient to code any network configuration with two sources as a function of the number of receivers in the network. But perhaps the most significant strength of our approach concerns future network coding practice. Namely, we propose deterministic algorithms to specify the coding operations at network nodes without the knowledge of the overall network topology. Such decentralized designs facilitate the construction of codes that can easily accommodate future changes in the network, e.g., addition of receivers and loss of links.
Once Upon a Polymorphic Type
, 1998
"... We present a sound typebased `usage analysis' for a realistic lazy functional language. Accurate information on the usage of program subexpressions in a lazy functional language permits a compiler to perform a number of useful optimisations. However, existing analyses are either adhoc and approxim ..."
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Cited by 38 (5 self)
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We present a sound typebased `usage analysis' for a realistic lazy functional language. Accurate information on the usage of program subexpressions in a lazy functional language permits a compiler to perform a number of useful optimisations. However, existing analyses are either adhoc and approximate, or defined over restricted languages. Our work extends the Once Upon A Type system of Turner, Mossin, and Wadler (FPCA'95). Firstly, we add type polymorphism, an essential feature of typed functional programming languages. Secondly, we include general Haskellstyle userdefined algebraic data types. Thirdly, we explain and solve the `poisoning problem', which causes the earlier analysis to yield poor results. Interesting design choices turn up in each of these areas. Our analysis is sound with respect to a Launchburystyle operational semantics, and it is straightforward to implement. Good results have been obtained from a prototype implementation, and we are currently integrating the system into the Glasgow Haskell Compiler.
Pathbased depthfirst search for strong and biconnected components
 Information Processing Letters
, 2000
"... Key words: Graph, depthfirst search, strongly connected component, biconnected component, stack. ..."
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Cited by 30 (0 self)
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Key words: Graph, depthfirst search, strongly connected component, biconnected component, stack.
Formal Foundations for ObjectOriented Data Modeling
 IEEE Transactions on Knowledge and Data Engineering
, 1993
"... We give an axiomatic definition of the basic structure, called a class dictionary graph, used by objectoriented designers and programmers during the software development process. The contributions of this paper are twofold: An axiomatic foundation for objectoriented data modeling and efficient a ..."
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Cited by 28 (17 self)
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We give an axiomatic definition of the basic structure, called a class dictionary graph, used by objectoriented designers and programmers during the software development process. The contributions of this paper are twofold: An axiomatic foundation for objectoriented data modeling and efficient algorithms for checking whether a given data model satisfies the axioms. The presented data model is the foundation of a number of techniques for developing objectoriented systems including adaptive software, schema abstraction from object examples, schema optimization, planning techniques for system development, the Law of Demeter, etc. Keywords: Objectoriented data modeling and programming, algorithms and tools for objectoriented design, axioms for data models, Demeter Method. 1 Introduction In objectoriented data modeling and programming, each entity of the problem domain is represented by a set of objects with relations and operations. Each object is composed of part objects/su...
A FirstOrder Isomorphism Theorem
 SIAM JOURNAL ON COMPUTING
, 1993
"... We show that for most complexity classes of interest, all sets complete under firstorder projections are isomorphic under firstorder isomorphisms. That is, a very restricted version of the BermanHartmanis Conjecture holds. ..."
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Cited by 24 (5 self)
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We show that for most complexity classes of interest, all sets complete under firstorder projections are isomorphic under firstorder isomorphisms. That is, a very restricted version of the BermanHartmanis Conjecture holds.