Suman Roy

An efficient XML to OWL converter

XML has become the de-facto standard of data exchange format in E-businesses. Although XML can support syntactic inter-operability, problems arise when data sources represented as XML documents are needed to be integrated. The reason is that XML lacks support for efficient sharing of conceptualization. The Web Ontology Language (OWL) can play an important role here as it can enable semantic inter-operability, and it supports the representation of domain knowledge using classes, properties and instances for applications. In many applications it is required to convert huge XML documents automatically to OWL ontologies, which is receiving a lot of attention. There are some existing converters for this job. Unfortunately they have serious shortcomings, e. g., they do not address the handling of characteristics like internal references, (transitive) import(s), include etc. which are commonly used in XML Schemas. To alleviate these drawbacks, we propose a new framework for mapping XML to OWL automatically. We illustrate our technique on examples to show the efficacy of our approach. We also provide the performance measures of our approach on some standard datasets. We also check the correctness of the conversion process.

A Finite State Analysis of Time-Triggered CAN (TTCAN) Protocol Using Spin

The paper presents a case study of the use of model checking for the analysis of an industrial protocol, a time triggered version of the CAN protocol (TTCAN). Our analysis of this protocol was carried out using the model checker Spin. The original CAN protocol can easily be modeled in Spin, but specifying TTCAN requires the provision of explicitly using time in the modeling language. With a view to express time triggered properties we use a discrete time version of Spin (DT-Spin). This extension allows one to quantify discrete time elapse between events by specifying the time slice in which they occur. Using DT-Spin we have been able to model TTCAN, and subsequently, verify a few of its time-triggered properties. This experience shows that it is possible to largely model TDMA-based protocols using discrete time

An Empirical Study of Error Patterns in Industrial Business Process Models

Business processes play an important role in organizations; however, not enough attention is given to analyzing and modeling errors in them. In this paper, we study syntactic and control flow error frequencies in business processes from real industry projects. Our samples come from a number of application domains such as Banking and Capital Markets, Insurance and Healthcare, and Retail. We consider industrial business processes modeled in Business Process Modeling Notation (BPMN) and use graph-theoretic techniques and Petri net-based analyses to detect syntactic and control flow-related errors, respectively. We then use a set of metrics that capture different network characteristics of the models and study the empirical relations between the metrics and process errors. The major results of the empirical investigation are: 1) multiple edges to or from tasks as well as hanging nodes are the predominant forms of syntactic errors, 2) syntactic errors occur frequently in Retail & Logistics domain and significantly less in the Insurance and Healthcare domain, and 3) the probability of error occurrence can be modeled as a function of node size and coefficient of connectivity through a logistic regression model which correctly classified 97.6 percent of the cases.

A finite state modeling of AFDX frame management using spin

Data exchange with strong data transmission time guarantees is necessary in the internal communication of an aircraft. The Avionics Full Duplex Switched Ethernet (AFDX) has been developed for this purpose. Its design is based on the principle of a switched network with physically redundant links to support availability. It should also be tolerant to transmission and link failures in the network. Recent research on an industrial case study by Anand et. al. reveals that AFDX frame management design is vulnerable to faults such as network errors, network babbling etc. Their proposed modifications, though are able to solve these problems, degrades the performance of network in terms of delay at receiving end and delay before the receiving end-system gets reset. They also do not present any performance analysis. We propose new solutions to alleviate these problems in AFDX frame management design, formally model it in Spin incorporating our proposed solution, thus also showing a finite state modeling of the above is possible. We also verify some of its relevant properties and carry out a performance analysis of the same.

Computationally and Resource Efficient Group Key Agreement for Ad Hoc Sensor Networks

Secure and reliable group communication is an important aspect of security in distributed ad hoc sensor networks. Most sensors are built to be inexpensive, low power devices and consequently have limited computational and communication resources. Constraints in resources make most conventional security protocols, such as Diffie-Hellman key exchange impractical. This work adapts existing work on tree-based group key agreement that combines key trees with Diffie-Hellman key exchange, by replacing expensive public key operations with relatively cheaper symmetric key operations. The modular exponentiations in Zn* used in Diffle-Hellman key exchange are replaced by polynomial evaluations in GF(2m) Galois fields, thereby reducing the code space and time complexity requirements for the protocols substantially. This makes the protocol adaptable for use on resource-constrained sensor networks. We also focus on secure and efficient group key management in the case of group mutation. Our group key management scheme will set up a per-session shared secret key among the group members when new members join or existing members leave the group. We also discuss a performance analysis of our scheme wherein we show that our protocol is efficient in terms of computational and memory requirements.

Timeout and calendar based finite state modeling and verification of real-time systems

We revisit the problem of real-time verification with dense time dynamics using timeout and calendar based models, originally proposed by Dutertre and Sorea, and simplify this to a finite state verification problem. To overcome the complexity of verification of real-time systems with dense time dynamics, Dutertre and Sorea, proposed timeout and calender based transition systems to model the behavior of real-time systems and verified safety properties using k-induction in association with bounded model checking. In this work, we introduce a specification formalism for these models in terms of Timed Transition Diagrams and capture their behavior in terms of semantics of Timed Transition Systems. Further, we discuss a technique, which reduces the problem of verification of qualitative temporal properties on infinite state space of (a large fragment of) these timeout and calender based transition systems into that on clockless finite state models through a two-step process comprising of digitization and canonical finitary reduction. This technique enables us to verify safety invariants for real-time systems using finite state model-checking avoiding the complexity of infinite state (bounded) model checking and scale up models without applying techniques from induction based proof methodology. Moreover, we can verify liveness properties for real-time systems, which is not possible by using induction with infinite state model checkers. We present examples of Fischer’s Protocol, Train-Gate Controller, and TTA start-up algorithm to illustrate how such an approach can be efficiently used for verifying safety, liveness, and timeliness properties specified in LTL using finite state model checkers like SAL-smc and Spin. We also demonstrate how advanced modeling concepts like inter-process scheduling, priorities, interrupts, urgent and committed location can be specified as extensions of the proposed specification formalism, that can be subjected to the proposed two step reduction technique for verification purposes.To overcome the complexity of verification of real-time systems with dense time dynamics, Dutertre and Sorea proposed timeout and calender based transition systems to model real-time systems and verify safety properties using k-induction. In this work, we propose a canonical finitary reduction technique, which reduces the infinite state space of timeout and calender based transition systems to a finite state space. The technique is formalized in terms of clockless finite state timeout and calendar based models represented as predicate transition diagrams. Using the proposed reduction, we can verify these systems using finite state model checkers and thus can avoid the complexity of induction based proof methodology. We present examples of Train-Gate Controller and the TTA startup algorithm to demonstrate how such an approach can be efficiently used for verifying safety, liveness, and timeliness properties using the finite state model checker Spin.

A ZKP-based identification scheme for base nodes in wireless sensor networks

Most of the published work on authentication mechanisms for wireless sensor networks establishes secure authentication for sensor nodes, but not for the base node that is in fact required to authenticate other nodes in the same network. This situation can lead to an attack whereby a malicious party masquerades as the base station and fraudulently authenticates other legitimate nodes to capture and/or inject messages within the network. The trust assumption in the existing literature with regard to base stations (i.e., implicitly trusting the base station) presents a serious security loophole. We address this problem by proposing a protocol that will help build a base station authentication mechanism in the framework of a one-hop mesh network and later extend it to a multi-hop framework. Our network would consist of a commissioning/installation device, and several forests of nodes (a base node and other nodes). The installation device would be responsible for deploying nodes in an area selected and would distribute information to them as necessary. We shall use a modification of the Guillou-Quisquater identification scheme as our Zero-Knowledge (ZK) protocol in conjunction with the μTESLA protocol for authenticated broadcast, to authenticate the base station.

Modeling and Verification of TTCAN Startup Protocol Using Synchronous Calendar

We describe the modeling and verification of TTCAN startup protocol using SAL model checker. For the modeling purposes we propose a new modeling framework called Synchronous Calendar which can be seen as an adaptation of Calendar based models introduced by Duterte and Sorea. A Synchronous Calendar can express dense time systems without relying on continuously varying clocks and supports synchronous message transmission. We capture both fault-free and fault-tolerant aspects of startup algorithm of TTCAN in two different models and verify the safety and liveness properties for them. Our verification technique relies on induction and abstraction methods which are supported by SAL model checker. To our knowledge this is the first work towards a formal analysis of TTCAN startup protocol.

A framework for security quantification of networked machines

Widespread application of computer network has evoked a lot of interest for cyber attackers to target these systems. In addition to cryptography based protective techniques such as authentication and authorization, several defense measures, like Intrusion Detection and Tolerance, and tools are employed to protect networks thereby, making security a critical issue. Therefore, the need for defining, structuring, and quantifying security arises as a necessary first step towards measuring the effectiveness of security related deployments. This work proposes a structured approach to define and analyze security related metrics for intrusion tolerant systems for each individual host in the network and compose them in a meaningful way to provide an overall security quantification for a network. The dynamics of each machine against a particular vulnerability is modeled as a (hidden) Markov process to capture uncertainties in attackers action and system response. Based on these stochastic analysis, security metrics of each machine are calculated which are subsequently used in the final computation of the security metrics of the network.1

Clustering and Labeling IT Maintenance Tickets

The goal of a Service System in an organization is to deliver uninterrupted service towards achieving business success. Ticketing system is an example of a Service System which is responsible for handling huge volumes of tickets generated by large enterprise IT (Information Technology) infrastructure components and ensuring smooth operation. Instead of manual screening one needs to extract information automatically from them to gain insights to improve operational efficiency. To ensure better operation we propose a framework to cluster incident tickets based on their textual context that can eliminate manual classification of them, which is labor intensive and costly. Further we label each of the clusters by generating meaningful keywords as logical itemsets, extracting candidate labels from Wikipedia articles, and finally scoring each of labels against each cluster. These labels can reflect an adequate and concise specification of each cluster. Further we experiment our approach with industrial ticket data from three different domains and report on the learned experience. We believe that our framework for clustering and labeling will enable enterprises to prioritize the issues in their IT infrastructure and improve the reliability and availability of their services.