Most of the work related to QoE maps objective variables (QoS-related) into a single one that predicts the quality the user perceives. In this paper we present a new approach to model multimedia OTT services, integrating not only the functional aspects of the service but also non-functional variables, which are classified into objective, subjective and business-related. Non-functional metrics might affect the Quality of Service (QoS), Quality of Experience (QoE) and Quality of Business (QoBiz) correspondingly. We also discuss how all these variables can be taken into account to predict the QoE of the service being studied. The functional requirements are modeled into a Timed Extended Finite State Machine (TEFSM), which is augmented with context variables (and their updating functions) representing non-functional requirements related to QoS, QoE and QoBiz. We use these parameters to evaluate the QoE using a trace model derived from the TEFSM previously built.

Conformance testing in network engineering is a crucial phase in the development of complex communicating systems. Model-based testing allows to automatize the testing process by generating test suites from a formal specification and to execute them on a real IUT. While many techniques have been developed, their application to test wireless routing ad-hoc protocols still raises many issues. The paper objective paper is to present the node self-similarity reducing the number of inconclusive verdicts often met in traditional MBT.

When a component of a discrete event system is faulty there is a problem how to locate a faulty component. In this paper, we consider the composition of two Extended Finite State Machines and propose an approach for locating a faulty component using preset and adaptive experiments with Finite State Machines.

The paper presents a parallel graph exploration algorithm. Automaton on a graph is an analogue of the Turing machine тАФ tape cells correspond to graph vertices, where the automaton can store some data, and moves along the tape correspond to moves along graph arcs. This system can be considered also as an aggregate of finite automatons located in graph vertices and interacting by message sending. Each automaton changes its state according to the data stored in the corresponding vertex, and moves along graph arcs are replaced with messages sent by the automaton of the arcтАЩs starting vertex to the one of the ending vertex. The suggested parallel graph exploration algorithm has worst case working time bound O(n/k+D), where n is the number of vertices, and D is the graph diameter, the maximum length of simple path (non-self intersecting path). As a result the algorithm builds two spanning trees of the graph: the direct spanning tree, which has the root vertex as its tree root and is directed from the root, and the back spanning tree, directed to the root.

The paper presents a parallel computation algorithm of an arbitrary function value on a multiset of values distributed on directed graph vertices. The computation is performed by message passing executed by automata distributed on the graph vertices. The key idea of the algorithm is to use a structural information on the graph that can be extracted by its parallel exploration and encoded into structures of direct and back spanning trees of the graph, which require only finite number of bits in each graph vertex, and to represent the function calculated as a composition of so called aggregate function and another one. Aggregate functions are characterized by possibility to calculate their value on a union of multisets by aggregating their values on separate multisets, that makes them easy for parallel computation.

In this paper, an approach for testing software implementations of telecommunication protocols based on tree finite state machines (FSM) is proposed. The first step is the extraction of the specification Extended FSM from an informal protocol description. The next step is to derive a corresponding EFSM l-equivalent that is a tree FSM. Based on the set of considered faults corresponding sequences of the l-equivalent are included into a test suite. The proposed approach is illustrated by protocol TCP (Windows).

This paper addresses the problem of minimizing a Finite State Machine (FSM) augmented with input and output timeouts, since almost all methods for deriving complete test suites are developed for reduced (minimal) timed machines, i.e., FSMs where every two states are not equivalent. If at some state no input is applied until the corresponding (input) timeout expires then the FSM can spontaneously move to another prescribed state. An output timeout describes the time that is necessary for executing a transition that is the number of time instances needed for producing an output after an input has been applied. A technique for minimizing such machines based on corresponding classical FSMs is proposed; it is also shown that differently from classical FSMs, an FSM with timeouts can have minimal forms which are not pair-wise isomorphic.

The problem of designing an unknown component that combined with the known part of a discrete event system satisfies the given overall specification arises in a number of applications. In this paper, we extend the known results for classical Finite State Machines (FSM) to Finite State Machines with Timeouts (TFSM). A TFSM is an FSM augmented with an input and an output timeout functions, prescribing the change of current state if no input is applied until a specified timeout expires and system delays needed to response to applied input, respectively. We represent the behavior of a TFSM by the corresponding regular language. The parallel composition of two TFSMs S and P is defined via composition of languages L(S) and L(P) intersected with L(MC), where MC is a maximal TFSM over input and output alphabets of the composition. The unknown component X is then designed as a solution to the equation where A and X are compared by ≤ with C. Here A is a context, C is a specification, and ≤ is the reduction relation which specifies that the behavior of a system to be designed is contained in that of the specification. Similar to classical FSMs, the equation is transformed to a language equation, the largest solution for which provides the largest solution to the solvable TFSM equation. After the largest solution is derived, a corresponding reduction can be extracted in order to provide the component with required properties. The application areas vary from testing in context to quality optimization of service compositions. Future work includes studying equation solvability criteria and properties of nondeterministic and partial specifications and solutions.

Wireless Sensor Networks (WSNs) emerge recently as one of the most attractive research subjects. The resource- constraint characteristics of WSNs limit the secure design and development of security protocols for them. Whilst, sensor nodes those usually operate in unattended and even harsh environments, are prone to failures and are vulnerable to malicious attacks. For reliable and secure communications in WSNs, intrusion-tolerant routing becomes a critical attribute that should be integrated into WSNs. In this paper, we study two intrusion- tolerant routing protocols for WSNs, namely INSENS and ITSRP, as well as analyze the intrusion-tolerant properties gained from these two propositions. Simulation and performance analysis have proved that both of them are practical.

Most FSM based methods for test derivation are developed for initialized Finite State Machines (FSM) and the latter means that a reliable reset is assumed in an implementation under test in order to glue test sequences together. If the reset is rather expensive then the number of test sequences has to be reduced and when it is reduced to a single sequence, this sequence is called a checking sequence. In this paper, a methods is proposed for deriving an adaptive checking sequence when the specification FSM is nondeterministic and the conformance relation is the reduction relation. The latter means that the behavior of a conforming implementation should be contained in the behavior of the specification. A method returns an adaptive checking sequence that detects each nonconforming implementation that has not more states than the specification FSM under the conditions that the specification has a distinguishing sequence and a deterministic strongly connected submachine. These conditions can be weakened for the case when the specification has a distinguishing test case and each state of the specification is definitely reachable from another state. The testing process is adaptive, i.e., the next input is determined based on the outputs produced for the previous inputs. Such adaptive distinguishing sequences can be shorter than preset checking sequences.

Collaborative systems are growing in use and popularity. The need to boost the methods concerning the interoperability is growing as well; therefore, trustworthy interactions of the different systems are a priority. The decision regarding with whom and how to interact with other users or applications depends on each system. We focus on providing trust verdicts by evaluating the behaviors of different agents, using distributed on-line network monitoring. This will provide trust management systems information regarding a trustee experience, for those trust management systems based on "soft trust". In this work, we propose a scalable evaluation method for any on-line network monitoring system, by using an auxiliary model, an extended finite state automaton (EFSA), and as well as other known methods to reduce the time complexity of the evaluation algorithm.