12323199
On Context-Specific Substitutability of Web Services
Web service substitution refers to the problem of identifying a service that can replace another service in the context of a composition with a specified functionality. Existing solutions to this problem rely on detecting the functional and behavioral equivalence of a particular service to be replaced and candidate services that could replace it. We introduce the notion of context-specific substitutability, where context refers to the overall functionality of the composition that is required to be maintained after replacement of its constituents. Using the context information, we investigate two variants of the substitution problem, namely environment-independent and environment- dependent, where environment refers to the constituents of a composition and show how the substitutability criteria can be relaxed within this model. We provide a logical formulation of the resulting criteria based on model checking techniques as well as prove the soundness and completeness of the proposed approach.
37245904
Model checking the Java meta-locking algorithm
We apply the XMC model checker to the Java meta-locking algorithm, a highly optimized technique for ensuring mutually exclusive access by threads to object monitor queues. Our abstract specification of the meta-locking algorithm is fully parameterized, both on M, the number of threads, and N, the number of objects. Using XMC, we show that for a variety of values of M and N, the algorithm indeed provides mutual exclusion and freedom from lockout.
15323130
MoSCoE: A Framework for Modeling Web Service Composition and Execution
Development of sound approaches and software tools for specification, assembly, and deployment of composite Web services from independently developed components promises to enhance collaborative software design and reuse. In this context, the proposed research introduces a new incremental approach to service composition, MoSCoE (Modeling Web Service Composition and Execution), based on the three steps of abstraction, composition and refinement. Abstraction refers to the high-level description of the service desired (goal) by the user, which drives the identification of an appropriate composition strategy. In the event that such a composition is not realizable, MoSCoE guides the user through successive refinements of the specification towards a realizable goal service that meets the user requirements.
16902988
A Cost-Sensitive Model for Preemptive Intrusion Response Systems
The proliferation of complex and fast-spreading intrusions not only requires advances in intrusion detection mechanisms but also demands development of sophisticated and automated intrusion response systems. In this paper we present a novel cost-sensitive model for intrusion response that incorporates preemptive deployment of the response actions. Specifically, our technique relies on comparing the cost of deploying a response against the cost of damage caused by an "'un-attended" intrusion and decides to preemptively deploy a response with maximum benefit. Our technique further allows adaptation of responses to the changing environment through evaluation of success and failure of previously triggered responses. We demonstrate the advantages of the approach and evaluate it using a damage reduction metric.
8152994
Localizing Program Errors for Cimple Debugging
We present automated techniques for the explanation of counter-examples, where a counter-example should be understood as a sequence of program statements. Our approach is based on variable dependency analysis and is applicable to programs written in Cimple, an expressive subset of the C programming language. Central to our approach is the derivation of a focus-statement sequence (FSS) from a given counter-example: a subsequence of the counter-example containing only those program statements that directly or indirectly affect the variable valuation leading to the program error behind the counter-example. We develop a ranking procedure for FSSs where FSSs of higher rank are conceptually easier to understand and correct than those of lower rank. We also analyze constraints over uninitialized variables in order to localize program errors to specific program segments; this often allows the user to subsequently take appropriate debugging measures. We have implemented our techniques in the FocusCheck model checker, which efficiently checks for assertion violations in Cimple programs on a per-procedure basis. The practical utility of our approach is illustrated by its successful application to a fast, linear-time median identification algorithm commonly used in statistical analysis and in the Resolution Advisory module of the Traffic Collision Avoidance System.
43133187
Parameterized Verification of pi-Calculus Systems
In this paper we present an automatic verification technique for parameterized systems where the subsystem behavior is modeled using the π-calculus. At its core, our technique treats each process instance in a system as a property transformer. Given a property ϕ that we want to verify of an N-process system, we use a partial model checker to infer the property ϕ′ (stated as a formula in a sufficiently rich logic) that must hold of an (N – 1)-process system. If the sequence of formulas ϕ,ϕ′,... thus constructed converges, and the limit is satisfied by the deadlocked process, we can conclude that the N-process system satisfies ϕ. To this end, we develop a partial model checker for the π-calculus that uses an expressive value-passing logic as the property language. We also develop a number of optimizations to make the model checker efficient enough for routine use, and a light-weight widening operator to accelerate convergence. We demonstrate the effectiveness of our technique by using it to verify properties of a wide variety of parameterized systems that are beyond the reach of existing techniques.
908197
WebSob: A Tool for Robustness Testing of Web Services
Web services are a popular way of implementing a service-oriented architecture. Testing can be used to help assure both the correctness and robustness of a web service. Because manual testing is tedious, tools are needed to automate test generation and execution for web services. This paper presents WebSob, a tool for automatically generating and executing web-service requests given a service provider's Web service description language (WSDL) specification. We have applied WebSob to freely available web services and our experiences show that WebSob can be used to quickly generate and execute web-service requests that may reveal robustness problems with no knowledge of the underlying web service implementation.
6329098
Web Service Dependency Discovery Tool for SOA Management
In this paper we identify the importance of the problem of discovering dynamic dependencies among Web services. The approach we take is to automate the identification of traces of dependent messages, based on the correlation of messages exchanged among services. We infer service dependencies based on the correlated message traces.
6997851
Computing the betti numbers of arrangements
(MATH) In this paper, we consider the problem of computing the Betti numbers of an arrangement of $n$ compact semi-algebraic sets, $S_1,\ldots,S_n \subset \R^k$, where each $S_i$ is described using a constant number of polynomials with degrees bounded by a constant. Such arrangements are ubiquitous in computational geometry. We give an algorithm for computing $\ell$-th Betti number, $\beta_\ell(\cup_i S_i), 0 \leq \ell \leq k-1$, using $O(n^{\ell+2})$ algebraic operations. Additionally, one has to perform linear algebra on matrices of size bounded by $O(n^{\ell+1})$. All previous algorithms for computing the Betti numbers of arrangements, triangulated the arrangement giving rise to a complex of size $O(n^{2^k})$ in the worst case. To our knowledge this is the first algorithm for computing $\beta_\ell(\cup_i S_i)$ that does not rely on such a global triangulation, and has a graded complexity which depends on $\ell$.
9474380
3D Modeling of Human Lip Motion
3023035
Computing the first few Betti numbers of semi-algebraic sets in single exponential time
Abstract In this paper we describe an algorithm that takes as input a description of a semi-algebraic set S ⊂ R k , defined by a Boolean formula with atoms of the form P > 0 , P 0 , P = 0 for P ∈ P ⊂ R [ X 1 , … , X k ] , and outputs the first l + 1 Betti numbers of S , b 0 ( S ) , … , b l ( S ) . The complexity of the algorithm is ( s d ) k O ( l ) , where s = # ( P ) and d = max P ∈ P deg ( P ) , which is singly exponential in k for l any fixed constant. Previously, singly exponential time algorithms were known only for computing the Euler–Poincare characteristic, the zeroth and the first Betti numbers.