28219085
Reducing Parametric Automata: A Multimedia Protocol Service Case Study
The Capability Exchange Signalling (CES) protocol is a control protocol for multimedia communications developed by the International Telecommunication Union (ITU) [3]. Our goal is to verify this protocol against the set of allowable sequences of service primitives (i.e. user observable events), known as the service language. Thus the first step to verify the CES protocol is to obtain the CES service language. By using automata reduction techniques [2], our approach is to extract the service language from the Occurrence Graph (OG) of the Coloured Petri Net (CPN) model [4] for the protocol’s service definition. The OG of a CPN model is a directed graph comprising all reachable states (nodes) and state changes (edges) of the model.
42350068
Tackling the Infinite State Space of a Multimedia Control Protocol Service Specification
Coloured Petri Nets (CPNs) are used to model the service provided by an International Standard for the control of multimedia communications over telecommunication networks including the Internet, known as the Capability Exchange Signalling (CES) protocol. The state space of the CPN model includes all of the possible sequences of user observable events, known as the service language, which is a useful baseline against which the protocol can be verified. However, the CES service CPN possesses an infinite state space, due to unbounded communication channels. We parameterize the CPN with the channel capacity, propose and prove a recursive formula for its state space and provide an algorithm for its construction. The algorithm generates the state space for capacity l, from the state space for capacity l - 1, providing incremental state space generation rather than generating a new state space for each value of l. The state space is linear in the size of the channel.
10550445
Fuzzy Bayesian Networks - A General Formalism for Representation, Inference and Learning with Hybrid Bayesian Networks
This paper proposes a general formalism for representation, inference and learning with general hybrid Bayesian networks in which continuous and discrete variables may appear anywhere in a directed acyclic graph. The formalism fuzzifies a hybrid Bayesian network into two alternative forms: the first form replaces each continuous variable in the given directed acyclic graph (DAG) by a partner discrete variable and adds a directed link from the partner discrete variable to the continuous one. The mapping between two variables is not crisp quantization but is approximated (fuzzified) by a conditional Gaussian (CG) distribution. The CG model is equivalent to a fuzzy set but no fuzzy logic formalism is employed. The conditional distribution of a discrete variable given its discrete parents is still assumed to be multinomial as in discrete Bayesian networks. The second form only replaces each continuous variable whose descendants include discrete variables by a partner discrete variable and adds a directed link from that partner discrete variable to the continuous one. The dependence between the partner discrete variable and the original continuous variable is approximated by a CG distribution, but the dependence between a continuous variable and its continuous and discrete parents is approximated by a conditional Gaussian regression (CGR) distribution. Obviously, the second form is a finer approximation, but restricted to CGR models, and requires more complicated inference and learning algorithms. This results in two general approximate representations of a general hybrid Bayesian networks, which are called here the fuzzy Bayesian network (FBN) form-I and form-II. For the two forms of FBN, general exact inference algorithms exists, which are extensions of the junction tree inference algorithm for discrete Bayesian networks. Learning fuzzy Bayesian networks from data is different from learning purely discrete Bayesian networks because not only all the newly converted discrete variables are latent in the data, but also the number of discrete states for each of these variables and the CG or CGR distribution of each continuous variable given its partner discrete parents or both continuous and discrete parents have to be determined.
24019518
Obtaining the service language for H.245's multimedia capability exchange signalling protocol: the final step
The capability exchange signalling (CES) protocol is a subprotocol of ITU-T recommendation H.245, "control protocol for multimedia communication". We are interested in verifying this protocol, including verification of its general properties such as absence of deadlocks and livelocks, and verification of the protocol against its service. In previous work, we have analysed the general properties of the CES protocol. In order to verify the protocol against its service, we need to generate the CES service language, which defines all the possible sequences of user observable events. We firstly create the CES service CPN model and then extract the language from the occurrence graph (OG) of the model. In the case of the CES service, this is challenging because we wish to have a general result for arbitrary capacity of the network over which the CES protocol operates. To tackle this problem we introduced into the CPN model a parameter, l, representing the capacity of the communication channel. We derived a recursive formula for the parameterised OG in terms of l. We treat this OG as a finite state automaton (FSA) by nominating acceptance states and apply FSA reduction algorithms to obtain a deterministic FSA that represents the CES service language. We have discovered a recursive formula in l for the CES service language. This paper introduces the CES service via its CPN model as necessary background and presents the final step of the proof of this finding.
11420663
Discovering and ranking web services with BASIL: a personalized approach with biased focus
In this paper we present a personalized web service discovery and ranking technique for discovering and ranking relevant data-intensive web services. Our first prototype -- called BASIL -- supports a <i>personalized</i> view of data-intensive web services through source-biased focus. BASIL provides service discovery and ranking through source-biased probing and source-biased relevance metrics. Concretely, the BASIL approach has three unique features: (1) It is able to determine in very few interactions whether a target service is relevant to the given source service by probing the target with very precise probes; (2) It can evaluate and rank the relevant services discovered based on a set of source-biased relevance metrics; and (3) It can identify interesting types of relationships for each source service with respect to other discovered services, which can be used as value-added metadata for each service. We also introduce a performance optimization technique called source-biased probing with focal terms to further improve the effectiveness of the basic source-biased service discovery algorithm. The paper concludes with a set of initial experiments showing the effectiveness of the BASIL system.
13142079
Domain-specific Web service discovery with service class descriptions
This paper presents DynaBot, a domain-specific Web service discovery system. The core idea of the DynaBot service discovery system is to use domain-specific service class descriptions powered by an intelligent Deep Web crawler. In contrast to current registry-based service discovery systems -like the several available UDDI registries - DynaBot promotes focused crawling of the Deep Web of services and discovers candidate services that are relevant to the domain of interest. It uses intelligent filtering algorithms to match services found by focused crawling with the domain-specific service class descriptions. We demonstrate the capability of DynaBot through the BLAST scenario and describe our initial experience with DynaBot.
17453773
Automatic 3D to 2D registration for the photorealistic rendering of urban scenes
This paper presents a novel and efficient algorithm for the 3D range to 2D image registration problem in urban scene settings. Our input is a set of unregistered 3D range scans and a set of unregistered and uncalibrated 2D images of the scene. The 3D range scans and 2D images capture real scenes in extremely high detail. A new automated algorithm calibrates each 2D image and computes an optimized transformation between the 2D images and 3D range scans. This transformation is based on a match of 3D with 2D features that maximizes an overlap criterion. Our algorithm attacks the hard 3D range to 2D image registration problem in a systematic, efficient, and automatic way. Images captured by a high-resolution 2D camera, that moves and adjusts freely, are mapped on a centimeter-accurate 3D model of the scene providing photorealistic renderings of high quality. We present results from experiments in three different urban settings.
6609876
MobiEyes: A Distributed Location Monitoring Service Using Moving Location Queries
With the growing popularity and availability of mobile communications, our ability to stay connected while on the move is becoming a reality instead of science fiction as it was just a decade ago. An important research challenge for modern location-based services is the scalable processing of location monitoring requests on a large collection of mobile objects. The centralized architecture, though studied extensively in literature, would create intolerable performance problems as the number of mobile objects grows significantly. This paper presents a distributed architecture and a suite of optimization techniques for scalable processing of continuously moving location queries. Moving location queries can be viewed as standing location tracking requests that continuously monitor the locations of mobile objects of interest and return a subset of mobile objects when certain conditions are met. We describe the design of MobiEyes, a distributed real time location monitoring system in a mobile environment. The main idea behind the MobiEyes' distributed architecture is to promote a careful partition of a real time location monitoring task into an optimal coordination of server-side processing and client-side processing. Such a partition allows evaluating moving location queries with a high degree of precision using a small number of location updates, thus providing highly scalable location monitoring services. A set of optimization techniques are used to limit the amount of computation to be handled by the mobile objects and enhance the overall performance and system utilization of MobiEyes. Important metrics to validate the proposed architecture and optimizations include messaging cost, server load, and amount of computation at individual mobile objects. We evaluate the scalability of the MobiEyes location monitoring approach using a simulation model based on a mobile setup. Our experimental results show that MobiEyes can lead to significant savings in terms of server load and messaging cost when compared to solutions relying on central processing of location information
10661094
Designing information systems in social context: a goal and scenario modelling approach
In order to design a better information system, a designer would like to have notations to visualize how design experts' know-how can be applied according to one's specific social and technology situation. We propose the combined use of a goal-oriented requirements language (GRL) and a scenario-oriented notation Use Case Maps (UCM) for representing design knowledge of information systems. Goal-oriented modelling is used throughout the requirements and design process. In GRL, goals are used to depict business objectives and system requirements, both functional and non-functional. Tasks are used to represent different ways for achieving goals. Means-ends reasoning is used to explore alternative solutions and their operationalizations into implementable system constructs. Social context is modelled in terms of dependency relationships among agents and roles. Scenarios expressed in UCM are used to describe elaborated business processes or workflow. The complementary use of goal-oriented modelling with GRL and scenario modelling with UCM is illustrated with an example of designing a web-based training system.