Hardness and inapproximability results for minimum verification set and minimum path decision tree problems

Minimization of decision trees is a well studied problem. In this work, we introduce two new problems related to minimization of decision trees. The problems are called minimum verification set (MinVS) and minimum path decision tree (MinPathDT) problems. Decision tree problems ask the question "What is the unknown given object?". MinVS problem on the other hand asks the question "Is the unknown object z?", for a given object z. Hence it is not an identification, but rather a verification problem. MinPathDT problem aims to construct a decision tree where only the cost of the root-to-leaf path corresponding to a given object is minimized, whereas decision tree problems in general try to minimize the overall cost of decision trees considering all the objects. Therefore, MinVS and MinPathDT are seemingly easier problems. However, in this work we prove that MinVS and MinPathDT problems are both NP-complete and cannot be approximated within a factor in o(lg n) unless P = NP

Using a SAT solver to generate checking sequences

Methods for software testing based on Finite State Machines (FSMs) have been researched since the early 60’s. Many of these methods are about generating a checking sequence from a given FSM which is an input sequence that determines whether an implementation of the FSM is faulty or correct. In this paper, we consider one of these methods, which constructs a checking sequence by reducing the problem of generating a checking sequence to finding a Chinese rural postman tour on a graph induced by the FSM; we re-formulate the constraints used in this method as a set of Boolean formulas; and use a SAT solver to generate a checking sequence of minimal length

Using distinguishing and UIO sequences together in a checking sequence

If a finite state machine M does not have a distinguishing sequence, but has UIO sequences for its states, there are methods to produce a checking sequence for M. However, if M has a distinguishing sequence D, then there are methods that make use of D to construct checking sequences that are much shorter than the ones that would be constructed by using only the UIO sequences for M. The methods to applied when a distinguishing sequence exists, only make use of the distinguishing sequences. In this paper we show that, even if M has a distinguishing sequence D, the UIO sequences can still be used together with D to construct shorter checking sequences

Checking sequence construction using adaptive and preset distinguishing sequences

Methods for testing from finite state machine-based specifications often require the existence of a preset distinguishing sequence for constructing checking sequences. It has been shown that an adaptive distinguishing sequence is sufficient for these methods. This result is significant because adaptive distinguishing sequences are strictly more common and up to exponentially shorter than preset ones. However, there has been no study on the actual effect of using adaptive distinguishing sequences on the length of checking sequences. This paper describes experiments that show that checking sequences constructed using adaptive distinguishing sequences are almost consistently shorter than those based on preset distinguishing sequences. This is investigated for three different checking sequence generation methods and the results obtained from an extensive experimental study are given

Minimizing coordination channels in distributed testing

Testing may be used to show that a system under test conforms to its specication. In the case of a distributed system, one may have to use a distributed test architecture, involving p testers in order to test the system under test. These p testers may under some circumstances have to coordinate their actions with each other using external coordination channels. This may require the use of up to p2 p unidirectional coordination channels in the test architecture, which can be an extensive and expensive setup. In this paper, we propose a method to generate checking sequences while minimizing the number of required coordination channels, by adapting existing methods that generate checking sequences to be applied in a centralized test architecture. We consider the case of unidirectional and bidirectional coordination channels, and the case of transitive coordination

High level rule modeling language for airline crew pairing

The crew pairing problem is an airline optimization problem where a set of least costly pairings (consecutive flights to be flown by a single crew) that covers every flight in a given flight network is sought. A pairing is defined by using a very complex set of feasibility rules imposed by international and national regulatory agencies, and also by the airline itself. The cost of a pairing is also defined by using complicated rules. When an optimization engine generates a sequence of flights from a given flight network, it has to check all these feasibility rules to ensure whether the sequence forms a valid pairing. Likewise, the engine needs to calculate the cost of the pairing by using certain rules. However, the rules used for checking the feasibility and calculating the costs are usually not static. Furthermore, the airline companies carry out what-if-type analyses through testing several alternate scenarios in each planning period. Therefore, embedding the implementation of feasibility checking and cost calculation rules into the source code of the optimization engine is not a practical approach. In this work, a high level language called ARUS is introduced for describing the feasibility and cost calculation rules. A compiler for ARUS is also implemented in this work to generate a dynamic link library to be used by crew pairing optimization engines

A novel GNSS repeater architecture for indoor positioning systems in ISM band

For indoor positioning using customary Global Navigation Satellite Systems (GNSS) receivers, the use of GNSS repeaters can be considered. However, regulations and provisions limit the use of GNSSrepeaters. In order to circumvent these limitations, we propose a novel repeater architecture that transmits the Global Positioning System (GPS)signals in433 MHz ISM bandby frequency down-conversion.In addition,areceiver front end is proposed to upconvert GPS signals back to 1575.42 MHz, which allows any off-the-shelf GPS receiver to be used for indoor positioning.Measurement results with the RF hardware show that when the GPS signals are down-converted and then upconverted back to its original frequency, GPS signal fidelity and positioning accuracy are preserved

Using synchronizing heuristics to construct homing sequences

Computing a shortest synchronizing sequence of an automaton is an NP-Hard problem. There are well-known heuristics to find short synchronizing sequences. Finding a shortest homing sequence is also an NP-Hard problem. Unlike existing heuristics to find synchronizing sequences, homing heuristics are not widely studied. In this paper, we discover a relation between synchronizing and homing sequences by creating an automaton called homing automaton. By applying synchronizing heuristics on this automaton we get short homing sequences. Furthermore, we adapt some of the synchronizing heuristics to construct homing sequences

An implementation of SDL 92 communication semantics

. The paper describes an abstract implementation of SDL communication semantics in the larger context of a design of SDL 92 simulation and verification tools. SDL signal exchange involves routing for signal traffic that allows for nondeterminism in communication path selection. The communication path selected may additionally be subject to a path constraint using SDL's via construct. We describe first a straightforward decomposition of an SDL program in a CSP like process algebra called ERPAL, and then reduce it to the final ERPAL model by eliminating the no-delay channels, signal routes and gates. The reduction involved simplifies the implementation and yet preserves the intended SDL semantics. Keywords : Communication Software , Specification Languages, Software Engineering, Compilers 1. Introduction This paper is a product of ongoing research activity aimed at developing a software platform around the specification language SDL 92 [6]. Currently the main tools under implementation..

Dependence analysis for regression test suite selection and augmentation

Using dependence analysis for model-based regression test suite (RTS) selection and augmentation from Extended Finite State Machine (EFSM) representations of system requirements is proposed. Given an EFSM representing the requirements of a system under test (SUT) and a set of modifications (i.e., adding, deleting, and changing transitions) on the EFSM, dependencies between transitions in the EFSM are identified. These dependencies capture the effects of the model on the modifications, the effects of the modifications on the model, and the side-effects of the modifications. The proposed method selects and augments a subset of a given test suite to form an RTS by examining dependencies covered by test cases in the given test suite