class switching according to nearest enemy distance for learning from highly imbalanced data sets abstract the imbalanced data classification has been deeply studied by the machine learning practitioners over the years and it is one of the most challenging problems in the field in many real life situations the under representation of a class in contrary to the rest commonly produces the tendency to ignore the minority class this being normally the target of the problem consequently many different techniques have been proposed among those the ensemble approaches have resulted to be very reliable new ways of generating ensembles have also been studied for standard classification in particular class switching as a mechanism to produce training perturbed sets has been proved to perform well in slightly imbalanced scenarios in this paper we analyze its potential to deal with highly imbalanced problems fighting against its major limitations we introduce a novel ensemble approach based on switching with a new technique to select the switched examples based on nearest enemy distance we compare the resulting switchingned with five distinctive ensemble based approaches with different combinations of sampling techniques with a better performance switchingned is settled as one of best approaches on the field

fuzzy rough classifiers for class imbalanced multi instance data in multi instance learning each learning object consists of many descriptive instances in the corresponding classification problems each training object is labeled but its constituent instances are not the classification objective is to predict the class label of unseen objects as in traditional single instance classification when the class sizes of multi instance data are imbalanced classification is degraded many multi instance classifiers have been proposed but few take into account the possibility of class imbalance which causes them to fail in this situation in this paper we propose a new type of classifier that embodies a solution to the multi instance class imbalance problem our proposal relies on the use of fuzzy rough set theory we present two families of classifiers respectively based on information extracted at bag level and at instance level we experimentally show that our algorithms outperform state of the art solutions to multi instance imbalanced data classification evaluated by the popular metrics auc and geometric mean highlightswe propose a new type of classifier for imbalanced multi instance data our classification method is based on fuzzy rough set theory we develop a framework consisting of two classifier families our proposal is experimentally shown to outperform the state of the art

axiomatizing prefix iteration with silent steps prefix iteration is a variation on the original binary version of the kleene star operationp q obtained by restricting the first argument to be an atomic action the interaction of prefix iteration with silent steps is studied in the setting of milner s basic ccs complete equational axiomatizations are given for four notions of behavioural congruence over basic ccs with prefix iteration viz branching congruence congruence delay congruence and weak congruence the completeness proofs for delay and weak congruence are obtained by reduction to the completeness theorem for branching congruence it is also argued that the use of the completeness result for branching congruence in obtaining the completeness result for weak congruence leads to a considerable simplification with respect to the only direct proof presented in the literature the preliminaries and the completeness proofs focus on open terms i e terms that may contain process variables as a by product the completeness of the axiomatizations is obtained as well as their completeness for closed terms

ordered sos process languages for branching and eager bisimulation we present a general and uniform method for defining structural operational semantics sos of process operators by traditional plotkin style transition rules equipped with orderings this new feature allows one to control the order of application of rules when deriving transitions of process terms our method is powerful enough to deal with rules with negative premises and copying we show that rules with orderings called ordered sos rules have the same expressive power as gsos rules we identify several classes of process languages with operators defined by rules with and without orderings in the setting with silent actions and divergence we prove that branching bisimulation and eager bisimulation relations are preserved by all operators in process languages in the relevant classes

generalized liouville property for schrodinger operator on riemannian manifolds in this paper we prove that the dimension of the space of positive bounded respectively mathcal l harmonic functions on a complete riemannian manifold with mathcal l regular ends is equal to the number of ends mathcal l nonparabolic ends respectively this result is a solution of an open problem of grigor yan related to the liouville property for the schrodinger operator mathcal l we also prove that if a given complete riemannian manifold is roughly isometric to a complete riemannian manifold satisfying the volume doubling condition the poincare inequality and the finite covering condition on each end then the dimension of the space of positive bounded respectively solutions for the schrodinger operator with a potential satisfying a certain decay rate on the manifold is equal to the number of ends mathcal l nonparabolic ends respectively this is a partial answer of the question suggested by li related to the regularity of ends of a complete riemannian manifold especially our results directly generalize various earlier results of yau of li and tam of grigor yan and of present authors but with different techniques that the peculiarity of the schrodinger operator demands

iterative boolean combination of classifiers in the roc space an application to anomaly detection with hmms hidden markov models hmms have been shown to provide a high level performance for detecting anomalies in sequences of system calls to the operating system kernel using boolean conjunction and disjunction functions to combine the responses of multiple hmms in the roc space may significantly improve performance over a single best hmm however these techniques assume that the classifiers are conditional independent and their of roc curves are convex these assumptions are violated in most real world applications especially when classifiers are designed using limited and imbalanced training data in this paper the iterative boolean combination ibc technique is proposed for efficient fusion of the responses from multiple classifiers in the roc space it applies all boolean functions to combine the roc curves corresponding to multiple classifiers requires no prior assumptions and its time complexity is linear with the number of classifiers the results of computer simulations conducted on both synthetic and real world host based intrusion detection data indicate that the ibc of responses from multiple hmms can achieve a significantly higher level of performance than the boolean conjunction and disjunction combinations especially when training data are limited and imbalanced the proposed ibc is general in that it can be employed to combine diverse responses of any crisp or soft one or two class classifiers and for wide range of application domains

a comprehensive study of fuzzy covering based rough set models definitions properties and interrelationships abstract fuzzy covering based rough set models are hybrid models using both rough set and fuzzy set theory the former is often used to deal with uncertain and incomplete information while the latter is used to describe vague concepts the study of fuzzy rough set models has provided very good tools for machine learning algorithms such as feature and instance selection in this article we discuss different types of dual fuzzy rough set models which all consider fuzzy coverings in particular we study two models using non nested level based representation of fuzziness in addition to the study of the theoretical properties for each model interrelationships between the different models are discussed resulting in a hasse diagram of fuzzy covering based rough set models for a finite fuzzy covering an imtl t norm and its residual implicator

structural operational semantics for weak bisimulations in this study we present rule formats for four main notions of bisimulation with silent moves weak bisimulation is a congruence for any process algebra defined by wb cool rules we have similar results for rooted weak bisimulation milner s observational equivalence branching bisimulation and rooted branching bisimulation the theorems stating that say observational equivalence is an appropriate notion of equality for ccs are corollaries of the results of this paper we also give sufficient conditions under which equational axiom systems can be generated from operational rules indeed many equational axiom systems appearing in the literature are instances of this general theory

a study of the behaviour of linguistic fuzzy rule based classification systems in the framework of imbalanced data sets in the field of classification problems we often encounter classes with a very different percentage of patterns between them classes with a high pattern percentage and classes with a low pattern percentage these problems receive the name of classification problems with imbalanced data sets in this paper we study the behaviour of fuzzy rule based classification systems in the framework of imbalanced data sets focusing on the synergy with the preprocessing mechanisms of instances and the configuration of fuzzy rule based classification systems we will analyse the necessity of applying a preprocessing step to deal with the problem of imbalanced data sets regarding the components of the fuzzy rule base classification system we are interested in the granularity of the fuzzy partitions the use of distinct conjunction operators the application of some approaches to compute the rule weights and the use of different fuzzy reasoning methods

analytic and geometric background of recurrence and non explosion of the brownian motion on riemannian manifolds we provide an overview of such properties of the brownian motion on complete non compact riemannian manifolds as recurrence and non explosion it is shown that both properties have various analytic characterizations in terms of the heat kernel green function liouville properties etc on the other hand we consider a number of geometric conditions such as the volume growth isoperimetric inequalities curvature bounds etc which are related to recurrence and non explosion

two finite specifications of a queue it is known that a queue is not finitely definable in acp with handshaking communication baeten and berg a 1988 in this paper two finite specifications of a queue in acp with abstraction and handshaking are proved correct relative to a standard specification of a queue that employs an infinite data type for representing its contents the proofs are given in the proof theory of rl and the only t laws used are xt x and x z jj z y x v z therefore the proofs are adequate for both branching bisimilarity and observation equivalence additionally it is shown that standard concurrency follows from rsp for a class of processes guardedly specifiable in acp with abstraction

mining data with random forests a survey and results of new tests random forests rf has become a popular technique for classification prediction studying variable importance variable selection and outlier detection there are numerous application examples of rf in a variety of fields several large scale comparisons including rf have been performed there are numerous articles where variable importance evaluations based on the variable importance measures available from rf are used for data exploration and understanding apart from the literature survey in rf area this paper also presents results of new tests regarding variable rankings based on rf variable importance measures we studied experimentally the consistency and generality of such rankings results of the studies indicate that there is no evidence supporting the belief in generality of such rankings a high variance of variable importance evaluations was observed in the case of small number of trees and small data sets

bisimulation can t be traced in the concurrent language ccs two programs are considered the same if they are bisimilar several years and many researchers have demonstrated that the theory of bisimulation is mathematically appealing and useful in practice however bisimulation makes too many distinctions between programs we consider the problem of adding operations to ccs to make bisimulation fully abstract we define the class of gsos operations generalizing the style and technical advantages of ccs operations we characterize gsos congruence in as a bisimulation like relation called ready simulation bisimulation is strictly finer than ready simulation and hence not a congruence for any gsos language

branching bisimulation congruence for probabilistic systems a notion of branching bisimilarity for the alternating model of probabilistic systems compatible with parallel composition is defined for a congruence result an internal transition immediately followed by a non trivial probability distribution is not considered inert a weaker definition of branching bisimilarity for the same model has been given earlier here we show that our branching bisimulation is the coarsest congruence for parallel composition that is included in the weaker version to support the use of the present equivalence as a reduction technique we also show that probabilistic ctl formulae are preserved by our equivalence and we provide a polynomial time algorithm deciding branching bisimilarity

a random forests quantile classifier for class imbalanced data abstract extending previous work on quantile classifiers q classifiers we propose the q classifier for the class imbalance problem the classifier assigns a sample to the minority class if the minority class conditional probability exceeds 0

ccs expressions finite state processes and three problems of equivalence abstract we examine the computational complexity of testing finite state processes for equivalence in milner s calculus of communicating systems ccs the equivalence problems in ccs are presented as refinements of the familiar problem of testing whether two nondeterministic finite automata nfa are equivalent i e accept the same language three notions of equivalence proposed for ccs are investigated namely observational equivalence strong observational equivalence and failure equivalence we show that observational equivalence can be tested in polynomial time as defined in ccs observational equivalence is the limit of a sequence of successively finer equivalence relations k where 1 is nondeterministic finite automaton equivalence we prove that for each fixed k deciding k is pspace complete we show that strong observational equivalence can be decided in polynomial time by reducing it to generalized partitioning a new combinatorial problem of independent interest finally we demonstrate that testing for failure equivalence is pspace complete even for a very restricted type of process

divide and congruence ii from decomposition of modal formulas to preservation of delay and weak bisimilarity abstract earlier we presented a method to decompose modal formulas for processes with the internal action and congruence formats for branching and bisimilarity were derived on the basis of this decomposition method the idea is that a congruence format for a semantics must ensure that the formulas in the modal characterisation of this semantics are always decomposed into formulas that are again in this modal characterisation in this follow up paper the decomposition method is enhanced to deal with modal characterisations that contain a modality a to derive congruence formats for delay and weak bisimilarity

three logics for branching bisimulation three temporal logics are introduced that induce on labeled transition systems the same identifications as branching bisimulation a behavioral equivalence that aims at ignoring invisible transitions while preserving the branching structure of systems the first logic is an extension of hennessy milner logic with an until operator the second one is another extension of hennessy milner logic which exploits the power of backward modalities the third logic is ctl without the next time operator a relevant side effect of the last characterization is that it sets a bridge between the state and action based approaches to the semantics of concurrent systems

undecidable equivalences for basic process algebra abstract a recent theorem shows that strong bisimilarity is decidable for the class of normed bpa processes which correspond to a class of context free grammars generating the free context free languages huynh and tian technical report utdcs 31 90 university of texas at dallas 1990 have shown that readiness and failure equivalence are undecidable for bpa processes in this paper we examine all other equivalences in the linear branching time hierarchy and show that none of them are decidable for normed bpa processes

deciding observational congruence of finite state ccs expressions by rewriting abstract we propose a term rewriting approach to verify observational congruence between guarded recursive finite state ccs expressions starting from the complete axiomatization of observational congruence for this subset of ccs a non terminating rewriting relation has been defined this rewriting relation is canonical over a subclass of infinite derivations structured fair derivations which compute all the normal forms the rewriting relation is shown to be complete with respect to the axiomatization by proving that every structured fair derivation computes a term that denotes an r normal process graph the existence of a finite representation for normal forms allows the definition of a rewriting strategy that in a finite number of rewriting steps decides observational congruence of guarded recursive finite state ccs expressions

classification by pairwise coupling we discuss a strategy for polychotomous classification that involves estimating class probabilities for each pair of classes and then coupling the estimates together the coupling model is similar to the bradley terry method for paired comparisons we study the nature of the class probability estimates that arise and examine the performance of the procedure in real and simulated data sets classifiers used include linear discriminants nearest neighbors adaptive nonlinear methods and the support vector machine

branching bisimulation for probabilistic systems characteristics and decidability we address the concept of abstraction in the setting of probabilistic reactive systems and study its formal underpinnings for the strictly alternating model of hansson in particular we define the notion of branching bisimilarity and study its properties by studying two other equivalence relations viz coloured trace equivalence and branching bisimilarity using maximal probabilities we show that both alternatives coincide with branching bisimilarity the alternative characterisations have their own merits and focus on different aspects of branching bisimilarity coloured trace equivalence can be understood without knowledge of probability theory and is independent of the notion of a scheduler branching bisimilarity rephrased in terms of maximal probabilities gives rise to an algorithm of polynomial complexity for deciding the equivalence together they give a better understanding of branching bisimilarity furthermore we show that the notions of branching bisimilarity in the alternating model of hansson and in the nonalternating model of segala differ branching bisimilarity in the latter setting turns out to discriminate between systems that are intuitively branching bisimilar

verification of reactive systems via instantiation of parameterised boolean equation systems verification problems for finite and infinite state processes like model checking and equivalence checking can effectively be encoded in parameterised boolean equation systems pbess solving the pbes then solves the encoded problem the decidability of solving a pbes depends on the data sorts that occur in the pbes we describe a pragmatic methodology for solving pbess viz by attempting to instantiate them to the sub fragment of boolean equation systems bess unlike solving pbess solving bess is a decidable problem based on instantiation verification using pbess can effectively be done fully automatically in most practical cases we demonstrate this by solving several complex verification problems using a prototype implementation of our instantiation technique in addition practical issues concerning this implementation are addressed furthermore we illustrate the effectiveness of instantiation as a transformation on pbess when solving verification problems involving systems of infinite size

axiomatizing weak simulation semantics over bccsp this paper is devoted to the study of the in equational theory of the largest pre congruences over the language bccsp induced by variations on the classic simulation preorder and equivalence that abstract from internal steps in process behaviours in particular the article focuses on the pre congruences associated with the weak simulation the weak complete simulation and the weak ready simulation preorders we present results on the non existence of finite ground complete in equational axiomatizations for each of these behavioural semantics the axiomatization of those semantics using conditional equations is also discussed in some detail

testing equivalences for processes abstract given a set of processes and a set of tests on these processes we show how to define in a natural way three different equivalences on processes these equivalences are applied to a particular language ccs we give associated complete proof systems and fully abstract models these models have a simple representation in terms of trees

on cool congruence formats for weak bisimulations in tcs 146 bard bloom presented rule formats for four main notions of bisimulation with silent moves he proved that weak bisimulation equivalence is a congruence for any process algebra defined by wb cool rules and established similar results for rooted weak bisimulation milner s observational congruence branching bisimulation and rooted branching bisimulation this study reformulates bloom s results in a more accessible form and contributes analogues for rooted bisimulation and rooted delay bisimulation moreover finite equational axiomatisations of rooted weak bisimulation equivalence are provided that are sound and complete for finite processes in any rwb cool process algebra these require the introduction of auxiliary operators with lookahead and an extension of bloom s formats for this type of operator with lookahead finally a challenge is presented for which bloom s formats fall short and further improvement is called for

theory of interaction abstract theory of interaction aims to provide a foundational framework for computation and interaction it proposes four fundamental principles that characterize the common features of all models of computation and interaction these principles suffice to support a model independent treatment of the two most important relationships in computer science the equality between processes and the relative expressiveness between models based on the two relationships the theory of equality the theory of expressiveness and the theory of completeness are developed

a general conservative extension theorem in process algebras with inequalities we prove a general conservative extension theorem for transition system based process theories with easy to check and reasonable conditions the core of this result is another general theorem which gives sufficient conditions for a system of operational rules and an extension of it in order to ensure conservativity that is provable transitions from an original term in the extension are the same as in the original system as a simple corollary of the conservative extension theorem we prove a completeness theorem we also prove a general theorem giving sufficient conditions to reduce the question of ground confluence modulo some equations for a large term rewriting system associated with an equational process theory to a small term rewriting system under the condition that the large system is a conservative extension of the small one we provide many applications to show that our results are useful the applications include but are not limited to various real and discrete time settings in acp atp and ccs and the notions projection renaming stage operator priority recursion the silent step autonomous actions the empty process divergence etc

absolute versus relative time in process algebras abstract timed process algebras are useful tools for the specification and verification of real time systems we study the relationships between two of these algebras c i pa closed interval process algebra and tccs temporal ccs which deal with temporal aspects of concurrent systems by following very different interpretations durational actions versus durationless actions absolute time versus relative time timed functional behavior versus time and functional behavior local clocks versus global clocks we show that these different choices are not irreconcilable by presenting simple mappings from c i pa to tccs which preserve the behavioral equivalences over the two timed calculi these results hold whenever basic actions are interpreted as either eager or lazy whenever the starting time of action execution is observed rather than their completion time a study on the size of the labelled transition systems describing the transitional semantics of cipa processes and those describing the transitional semantics of their translated versions is also presented

divide and congruence from decomposition of modal formulas to preservation of branching and η bisimilarity we present a method for decomposing modal formulas for processes with the internal action t to decide whether a process algebra term satisfies a modal formula one can check whether its subterms satisfy formulas that are obtained by decomposing the original formula the decomposition uses the structural operational semantics that underlies the process algebra we use this decomposition method to derive congruence formats for two weak and rooted weak semantics branching and h bisimilarity

a non parametric approach to extending generic binary classifiers for multi classification ensemble methods which combine generic binary classifier scores to generate a multi classification output are commonly used in state of the art computer vision and pattern recognition systems that rely on multi classification in particular we consider the one vs one decomposition of the multi class problem where binary classifier models are trained to discriminate every class pair we describe a robust multi classification pipeline which at a high level involves projecting binary classifier scores into compact orthogonal subspaces followed by a non linear probabilistic multi classification step using kernel density estimation kde we compare our approach against state of the art ensemble methods dcs drcw on 16 multi class datasets we also compare against the most commonly used ensemble methods vote nest on 6 real world computer vision datasets finally we measure the statistical significance of our approach using non parametric tests experimental results show that our approach gives a statistically significant improvement in multi classification performance over state of the art highlightsensemble methods combine binary classifiers to yield a multi classification output one vs one ensemble binary classifiers trained to discriminate each class pair we propose a robust non parametric probabilistic one vs one ensemble method kdemrp kdemrp improves classification performance over state of the art dcs drcw kdemrp improvements are statistically significant

quantales finite observations and strong bisimulation abstract it has often been claimed that bisimulation makes distinctions that cannot be observed in practice abramsky and vickers proposed an algebraic framework based on quantales for describing observations on concurrent processes without hidden transitions and used it in order to provide an observational explanation of several process equivalences ranging from hoare trace equivalence to ready simulation we follow their approach and argue that strong bisimulation can be explained in the same way at least in the case of image computable labelled transition systems

boosted classification trees and class probability quantile estimation the standard by which binary classifiers are usually judged misclassification error assumes equal costs of misclassifying the two classes or equivalently classifying at the 1 2 quantile of the conditional class probability function p y 1 x boosted classification trees are known to perform quite well for such problems in this article we consider the use of standard off the shelf boosting for two more general problems 1 classification with unequal costs or equivalently classification at quantiles other than 1 2 and 2 estimation of the conditional class probability function p y 1 x we first examine whether the latter problem estimation of p y 1 x can be solved with logitboost and with adaboost when combined with a natural link function the answer is negative both approaches are often ineffective because they overfit p y 1 x even though they perform well as classifiers a major negative point of the present article is the disconnect between class probability estimation and classification next we consider the practice of over under sampling of the two classes we present an algorithm that uses adaboost in conjunction with over under sampling and jittering of the data jous boost this algorithm is simple yet successful and it preserves the advantage of relative protection against overfitting but for arbitrary misclassification costs and equivalently arbitrary quantile boundaries we then use collections of classifiers obtained from a grid of quantiles to form estimators of class probabilities the estimates of the class probabilities compare favorably to those obtained by a variety of methods across both simulated and real data sets

in defense of one vs all classification we consider the problem of multiclass classification our main thesis is that a simple one vs all scheme is as accurate as any other approach assuming that the underlying binary classifiers are well tuned regularized classifiers such as support vector machines this thesis is interesting in that it disagrees with a large body of recent published work on multiclass classification we support our position by means of a critical review of the existing literature a substantial collection of carefully controlled experimental work and theoretical arguments

on the tradeoff between compositionality and exactness in weak bisimilarity for integrated time markovian process calculi integrated time markovian process calculi rely on actions whose durations are quantied by exponentially distributed random variables the markovian bisimulation equivalences dened so far for these calculi treat exponentially timed internal actions like all the other actions because each such action has a nonzero duration and hence can be observed if it is executed between a pair of exponentially timed noninternal actions however no dierence may be noted at stationary state between a sequence of exponentially timed internal actions and a single exponentially timed internal action if their expected durations and execution probabilities coincide a fact exploited in hillston s weak isomorphism we show that milner s approach can be adapted on the basis of this fact so to derive a weak bisimulation equivalence for integrated time markovian process calculi up to a tradeo between compositionality and exactness inherent to the markovian setting the resulting weak markovian bisimulation equivalence induces a pseudo aggregation that is exact at stationary state for all the considered processes but turns out to be a congruence only over sequential processes to achieve compositionality over concurrent processes we need to enhance the abstraction capability of the equivalence in the presence of interleaved computations however the corresponding pseudo aggregation turns out to be exact at stationary state only for a subset of concurrent processes in addition to this tradeo we present for the rst equivalence a sound and complete axiomatization over sequential processes which is instrumental to characterize pseudo aggregations and a polynomial time equivalence checking algorithm which can be exploited for the compositional minimization of concurrent processes

observation equivalence as a testing equivalence a notion of testing is developed for transition systems with divergence the forms of testing include traces refusals copying and global testing both denotational and operational formulations of testing are given the equivalence based on this notion of testing is shown to coincide with observation equivalence

bisimulation equivalence is decidable for all context free processes abstract a result originally due to baeten bergstra and klop shows that strong bisimulation equivalence for normed bpa processes is decidable on the other hand huynh and tian and groote and huttel have proved that all other standard equivalences are undecidable for normed bpa and thus for bpa in general the open problem remaining has been whether bisimulation is decidable for the full bpa language in this paper we answer this question in the affirmative using a proof technique based on the proof by caucal of the decidability of language equivalence for simple algebraic grammars the decision procedure relies on our main result extending that of caucal that the maximal bisimulation of any bpa transition graph is finitely representable as a thue congruence the decision procedure consists of two semi decision procedures one testing for non bisimilarity and one testing for bisimilarity

process algebra for performance evaluation this paper surveys the theoretical developments in the field of stochastic process algebras process algebras where action occurrences may be subject to a delay that is determined by a random variable a huge class of resource sharing systems like large scale computers client server architectures networks can accurately be described using such stochastic specification formalisms the main emphasis of this paper is the treatment of operational semantics notions of equivalence and sound and complete axiomatisations of these equivalences for different types of markovian process algebras where delays are governed by exponential distributions starting from a simple actionless algebra for describing time homogeneous continuous time markov chains we consider the integration of actions and random delays both as a single entity like in known markovian process algebras like tipp pepa and empa and as separate entities like in the timed process algebras timed csp and tccs in total we consider four related calculi and investigate their relationship to existing markovian process algebras we also briefly indicate how one can profit from the separation of time and actions when incorporating more general non markovian distributions

non regular iterators in process algebra we consider three forms of non regular iteration in process algebra the push down operation de5ned by x y x x y x y y the nesting operation de5ned by x y x x y x y and the back and forth operation de5ned by xy x xy y y in the process algebraic framework acp with abstraction and one of orwe provide de5nitions of the following standard processes stack context free process bag and queue these de5nitions apply to all standard behavioural equivalences we only use x x whereis the silent step moreover these results yield the expressive power to express computable processes modulo rooted branching bisimulation equivalence and hence support the equational founding of process algebra standard processes can be represented as terms c 2001 elsevier science b v all rights reserved

deciding bisimulation equivalences for a class of non finite state programs traditionally many automatic program verification techniques have been applicable only to finite state programs in this paper we extend some of these techniques to a class of infinite state programs that in addition to having a finite state control component may read store and write but not perform any other computations on data such programs are data independent in the sense that their behavior does not depend on the actual data values supplied we consider the problems of deciding strong equivalence and observation equivalence defined by bisimulations as in ccs between such programs these equivalences have major applications in verification of communication protocols we present reductions of these problems to the problem of deciding strong equivalence and observation equivalence between finite state programs for which polynomial time algorithms exist the equivalence problems on data independent programs are shown to be np hard in the size of the programs

process algebra with propositional signals we consider processes that have transitions labeled with atomic actions and states labeled with formulas over a propositional logic these state labels are called signals a process in a parallel composition may proceed conditionally dependent on the presence of a signal in the process in parallel this allows a natural treatment of signal observation

bisimulation and divergence abstract behavioural preorders based on the idea of bisimulation but refining the notion of bisimulation equivalence and providing explicit treatments of the phenomenon of divergence in communicating systems are investigated particular study is made of these preorders in the context of milner s calculus of communicating systems the precongruence relations generated by the preorders are characterized and axiomatized on the classes of finite closed terms and sequential terms a verification technique based on the theory of the preorders is introduced and illustrated

comparative branching time semantics for markov chains this paper presents various semantics in the branching time spectrum of discrete time and continuous time markov chains dtmcs and ctmcs strong and weak bisimulation equivalence and simulation preorders are covered and are logically characterized in terms of the temporal logics probabilistic computation tree logic pctl and continuous stochastic logic csl apart from presenting various existing branching time relations in a uniform manner this paper presents the following new results i strong simulation for ctmcs ii weak simulation for ctmcs and dtmcs iii logical characterizations thereof including weak bisimulation for dtmcs iv a relation between weak bisimulation and weak simulation equivalence and v various connections between equivalences and pre orders in the continuous and discrete time setting the results are summarized in a branching time spectrum for dtmcs and ctmcs elucidating their semantics as well as their relationship

a uniform framework for modeling nondeterministic probabilistic stochastic or mixed processes and their behavioral equivalences labeled transition systems are typically used as behavioral models of concurrent processes their labeled transitions define a one step state to state reachability relation this model can be generalized by modifying the transition relation to associate a state reachability distribution with any pair consisting of a source state and a transition label the state reachability distribution is a function mapping each possible target state to a value that expresses the degree of one step reachability of that state values are taken from a preordered set equipped with a minimum that denotes unreachability by selecting suitable preordered sets the resulting model called ultras from uniform labeled transition system can be specialized to capture well known models of fully nondeterministic processes lts fully probabilistic processes adtmc fully stochastic processes actmc and nondeterministic and probabilistic mdp or nondeterministic and stochastic ctmdp processes this uniform treatment of different behavioral models extends to behavioral equivalences they can be defined on ultras by relying on appropriate measure functions that express the degree of reachability of a set of states when performing multi step computations it is shown that the specializations of bisimulation trace and testing equivalences for the different classes of ultras coincide with the behavioral equivalences defined in the literature over traditional models except when nondeterminism and probability stochasticity coexist then new equivalences pop up

maximality preserving bisimulation abstract a new bisimulation notion is introduced for the specification of concurrent systems which resists to a large class of action refinements even in the presence of invisible actions the work is presented in the context of labelled p t nets but it may be transported to other popular frameworks like prime event structures process graphs etc

polynomial time decision algorithms for probabilistic automata deciding in an efficient way weak probabilistic bisimulation in the context of probabilistic automata is an open problem for about a decade in this work we close this problem by proposing a procedure that checks in polynomial time the existence of a weak combined transition satisfying the step condition of the bisimulation this enables us to arrive at a polynomial time algorithm for deciding weak probabilistic bisimulation and also branching probabilistic bisimulation we furthermore present several extensions to interesting related problems in particular weak and branching probabilistic simulation setting the ground for the development of more effective and compositional analysis algorithms for probabilistic systems

unique parallel decomposition in branching and weak bisimulation semantics we consider the property of unique parallel decomposition modulo branching and weak bisimilarity first we show that normed behaviours always have parallel decompositions but that these are not necessarily unique then we establish that finite behaviours have unique parallel decompositions we derive the latter result from a general theorem about unique decompositions in partial commutative monoids

process algebra with language matching abstract an axiom system acp lm is presented as a variant of the process algebra acp the acronym acp lm stands for acp with abstraction extended with operators and axioms for language matching language matching is a technique based on trace information for labelling and cutting off process terms that do not match some given language or set of traces it is shown that in combination with the axioms for action alphabets interesting results are derivable the most important of which is the redundancy theorem 3 3 6 which roughly states that if no trace labels occur in the expression h pl q where pl is a labelled version of some process p then it holds that h pl q h p q it is shown that under certain natural conditions a similar result holds when abstraction is applied to pl and p in order to illustrate the use of language matching the concurrent alternating bit protocol cabp is verified the cabp is a simple communication protocol which can be recursively specified over the signature of acp and it may be regarded as a slightly more sophisticated variant of the well known alternating bit protocol earlier studies of this protocol have already demonstrated that redundancies in a context make this protocol hard to verify our verification is carried out by means of acp with language matching extended with the abstraction rule cfar itb and the conditional alphabet axioms the verification is split into two parts so that it is modular and in the verification some basic knowledge about the expected behaviour of the system is used in order to allow the effective application of language matching

generalized harmonic functions of riemannian manifolds with ends we study l harmonic functions solutions of the stationary schrodinger equation on arbitrary noncompact riemannian manifolds with finitely many ends we establish some existence and uniqueness results and obtain sharp dimension estimates for l harmonic functions on such manifolds

partial confluence of processes and systems of objects a process calculus extending the calculus with higher order agent abstractions as in the higher order calculus and first order data other than names but with only first order interaction is used to give a natural and direct semantic definition for a concurrent object oriented programming language a notion of partial confluence of agents is introduced and its theory developed first in the setting of ccs and then in the mobile process calculus it is shown how the semantic definition can be used as a basis for reasoning about systems prescribed by programs of the language the theory of partial confluence is used to prove the indistinguishability in an arbitrary program context of two classes whose instances combine to form data structures only one of which supports concurrent operations

infinite normal forms for non linear term rewriting systems abstract nonterminating rewrite relations have recently been studied in order to set a framework within which infinite terms can be seen as limits of infinite converging derivations results about the existence of infinite normal forms have been given only for orthogonal term rewriting systems namely left linear and nonoverlapping systems in this paper we show that some of those results can be extended to a particular class of nonorthogonal term rewriting systems we deal with systems in which the nonterminating rules are unfolding rules that model the operational semantics of a recursive operator the left linearity requirement is replaced by a retraction property of the supporting term algebra that allows the definition of a rewrite relation modulo a congruence relation induced on the set of terms by the unfolding rules

characterizing finite kripke structures in propositional temporal logic abstract we show that if two finite kripke structures can be distinguished by some ctl formula that contains both branching time and linear time operators then the structures can be distinguished by a ctl formula that contains only branching time operators our proof involves showing that for any finite kripke structure m it is possible to construct a ctl formula f m that uniquely characterizes m since one kripke structure may be a trivial unrolling of another we use a notion of equivalence between kripke structures that is similar to the notion of bisimulation studied by milner 15 our first construction of f m requires the use of the nexttime operator we also consider the case in which the nexttime operator is disallowed in ctl formulas the proof in this case requires another notion of equivalence equivalence with respect to stuttering and is much more difficult since it is possible for two inequivalent states to have exactly the same finite behaviors modulo stuttering but different infinite behaviors we also give a polynomial algorithm for determining if two structures are stuttering equivalent and discuss the relevance of our results for temporal logic model checking and synthesis procedures

divide and congruence iii from decomposition of modal formulas to preservation of stability and divergence abstract in two earlier papers we derived congruence formats with regard to transition system specifications for weak semantics on the basis of a decomposition method for modal formulas the idea is that a congruence format for a semantics must ensure that the formulas in the modal characterisation of this semantics are always decomposed into formulas that are again in this modal characterisation the stability and divergence requirements that are imposed on many of the known weak semantics have so far been outside the realm of this method stability refers to the absence of a transition we show using the decomposition method how congruence formats can be relaxed for weak semantics that are stability respecting this relaxation for instance brings the priority operator within the range of the stability respecting branching bisimulation format divergence which refers to the presence of an infinite sequence of transitions escapes the inductive decomposition method we circumvent this problem by proving that a congruence format for a stability respecting weak semantics is also a congruence format for its divergence preserving counterpart

fuzzy rough nearest neighbour classification and prediction nearest neighbour nn approaches are inspired by the way humans make decisions comparing a test object to previously encountered samples in this paper we propose an nn algorithm that uses the lower and upper approximations from fuzzy rough set theory in order to classify test objects or predict their decision value it is shown experimentally that our method outperforms other nn approaches classical fuzzy and fuzzy rough ones and that it is competitive with leading classification and prediction methods moreover we show that the robustness of our methods against noise can be enhanced effectively by invoking the approximations of the vaguely quantified rough set vqrs model which emulates the linguistic quantifiers some and most from natural language

on the expressiveness of interaction subbisimilarity is proposed as a general tool to classify the relative expressive power of process calculi the expressiveness of several variants of ccs is compared in terms of the subbisimilarity relationship similar investigation is also carried out for the variants of the pi calculus the relative expressiveness of the different forms of the choice operation and the different ways of introducing infinite behaviors are systematically studied in both the frameworks of ccs and pi some issues concerning the expressiveness of both ccs and pi are clarified several open problems are solved along the way the subbisimilarity approach and the relative expressiveness results are applied to show the independence of the operators of the pi calculus the definition of the subbisimilarity relationship can be further strengthened with computational requirement leading to a uniform treatment of computation and interaction

algebraic laws for nondeterminism and concurrency since a nondeterministic and concurrent program may in general communicate repeatedly with its environment its meaning cannot be presented naturally as an input output function as is often done in the denotational approach to semantics in this paper an alternative is put forth first a definition is given of what it is for two programs or program parts to be equivalent for all observers then two program parts are said to be observation congruent if they are in all program contexts equivalent the behavior of a program part that is its meaning is defined to be its observation congruence class the paper demonstrates for a sequence of simple languages expressing finite terminating behaviors that in each case observation congruence can be axiomatized algebraically moreover with the addition of recursion and another simple extension the algebraic language described here becomes a calculus for writing and specifying concurrent programs and for proving their properties

next preserving branching bisimulation bisimulations are equivalence relations between transition systems which assure that certain aspects of the behaviour of the systems are the same in a related pair for many applications it is not possible to maintain such an equivalence unless non observable stuttering behaviour is ignored however existing bisimulation relations which permit the removal of non observable behaviour are unable to preserve temporal logic formulas referring to the next step operator in this paper we propose a family of next preserving branching bisimulations to overcome this limitation next preserving branching bisimulations are parameterised with a natural number indicating the nesting depth of the x operators that the bisimulation preserves while still allowing non observable behaviour to be reduced based on van glabbeek and weijland s notion of branching bisimulation with explicit divergence we define the novel parameterised relation for which we prove the preservation of ctl formulas with an x operator nesting depth that is not greater than the specified parameter it can be shown that the family of next preserving bisimulations constitutes a hierarchy that fills the gap between branching bisimulation and strong bisimulation as an example for its application we show how this definition gives rise to an advanced slicing procedure that creates a formula specific slice which constitutes a reduced model of the system that can be used as a substitute when verifying this formula the result is a novel procedure for generating slices that are next preserving branching bisimilar to the original model for any formula we can assure that each slice preserves the formula it corresponds to which renders the overall verification process sound

on complete manifolds with nonnegative ricci curvature complete open riemannian manifolds mn g with nonnegative sectional curvature are well understood the basic results are toponogov s splitting theorem and the soul theorem cg1 the splitting theorem has been extended to manifolds of nonnegative ricci curvature cg2 on the other hand the soul theorem does not extend even topologically according to recent examples in gm2 a different method to construct manifolds which carry a metric with ric 0 but no metric with nonnegative sectional curvature has been given by l berard bergery bb this leads to the question cf also y1 is there any finiteness result for complete riemannian manifolds with ric 0 the answer is certainly affirmative in the low dimensional special cases n 2 where all notions of curvature coincide and n 3 where nonnegative ricci curvature has been studied by means of stable minimal surfaces msy sy on the other hand j p sha and d g yang shy have constructed complete manifolds with strictly positive ricci curvature in higher dimensions for example they can choose the underlying space to be r4 x s3 with infinitely many copies of s3 x cp 2 attached to it by surgery cf also shy 1 it is therefore clear that any finiteness result for arbitrary dimensions requires additional assumptions the purpose of this paper is to establish the following main result

an extension on statistical comparisons of classifiers over multiple data sets for all pairwise comparisons in a recently published paper in jmlr dem sar 2006 recommends a set of non parametric statistical tests and procedures which can be safely used for comparing the performance of classifiers over multiple data sets after studying the paper we realize that the paper correctly introduces the basic procedures and some of the most advanced ones when comparing a control method however it does not deal with some advanced topics in depth regarding these topics we focus on more powerful proposals of statistical procedures for comparing n n classifiers moreover we illustrate an easy way of obtaining adjusted and comparable p values in multiple comparison procedures

calculi for synchrony and asynchrony abstract a calculus for distributed computation is studied based upon four combinators a central idea is an abelian group of actions which models the interfaces between components of a distributed computing agent using a notion of bisimulation congruence relations are defined over computing agents and thence an algebraic theory is derived the calculus models both synchronous and asynchronous computation in particular it is shown that the author s calculus of communicating systems 1980 which is an asynchronous model is derivable from the calculus presented here

branching time and abstraction in bisimulation semantics in comparative concurrency semantics one usually distinguishes between linear time and branching time semantic equivalences milner s notion of observatin equivalence is often mentioned as the standard example of a branching time equivalence in this paper we investigate whether observation equivalence really does respect the branching structure of processes and find that in the presence of the unobservable action of ccs this is not the case therefore the notion of branching bisimulation equivalence is introduced which strongly preserves the branching structure of processes in the sense that it preserves computations together with the potentials in all intermediate states that are passed through even if silent moves are involved on closed ccs terms branching bisimulation congruence can be completely axiomatized by the single axion scheme a y z y a y z where a ranges over all actions and the usual loaws for strong congruence we also establish that for sequential processes observation equivalence is not preserved under refinement of actions whereas branching bisimulation is for a large class of processes it turns out that branching bisimulation and observation equivalence are the same as far as we know all protocols that have been verified in the setting of observation equivalence happen to fit in this class and hence are also valid in the stronger setting of branching bisimulation equivalence

a partial order approach to branching time logic model checking abstract partial order techniques enable reducing the size of the state space used for model checking thus alleviating the state space explosion problem these reductions are based on selecting a subset of the enabled operations from each program state so far these methods have been studied implemented and demonstrated for assertional languages that model the executions of a program as computation sequences in particular the linear temporal logic the present paper shows for the first time how this approach can be applied to languages that model the behavior of a program as a tree we study here partial order reductions for branching temporal logics e g the logics ctl and ctl with the next time operator removed and process algebra logics such as hennesy milner logic with actions conditions on the selection of subset of successors from each state during the state space construction which guarantee reduction that preserves ctl properties are given the experimental results provided show that the reduction is substantial

modular specification of process algebras abstract this paper proposes a modular approach to the algebraic specification of process algebras this is done by means of the notion of a module the simplest modules are building blocks of operators and axioms each block describing a feature of concurrency in a certain semantical setting these modules can then be combined by means of a union operator an export operator allowing to forget some operators in a module an operator h changing semantics by taking homomorphic images and an operator s which takes subalgebras these operators enable us to combine modules in a subtle way when the direct combination would be inconsistent we give a presentation of equational logic infinitary conditional equational logic of which we also prove the completeness and first order logic and show how the notion of a formal proof of a formula from a theory can be generalized to that of a proof of a formula from a module this module logic is then applied in process algebra we show how auxiliary process algebra operators can be hidden when this is needed moreover we demonstrate how new process combinators can be defined in terms of more elementary ones in a clean way as an illutration of our approach we specify some fifo queues and verify several of their properties

register machine based processes we study extensions of the process algebra axiom system acp with two recursive operations the binary kleene star which is defined by x y x x y y and the push down operation defined by x y x x y x y y in this setting it is easy to represent register machine computation and an equational theory results that is not decidable in order to increase the expressive power abstraction is then added with rooted branching bisimulation equivalence each computable process can be expressed and with rooted o bisimilarity each semi computable process that initially is finitely branching can be expressed moreover with abstraction and a finite number of auxiliary actions these results can be obtained without binary kleene star finally we consider two alternatives for the push down operation each of these gives rise to similar results

timed process calculi with deterministic or stochastic delays several deterministically stochastically timed process calculi have been proposed in the literature that apart from their synchronization mechanism mainly differ for the way in which actions and delays are represented in particular a distinction is made between integrated time calculi in which actions are durational and orthogonal time calculi in which actions are instantaneous and delays are expressed separately in a previous work on deterministic time the two approaches have been shown to be reconcilable through an encoding from the integrated time calculus cipa to the orthogonal time calculus tccs which preserves strong timed bisimilarity under certain conditions in this paper the picture is completed by first defining a reverse encoding from tccs to cipa which requires slight modifications to both calculi and is shown to preserve only weak timed bisimilarity under conditions tighter than those for the direct encoding stochastic time is then addressed by exhibiting an encoding from the integrated time calculus mtipp to the orthogonal time calculus iml together with a reverse encoding requiring slight modifications only to the former calculus with both encodings being shown to preserve strong markovian bisimilarity under suitable conditions all the four encodings rely on the assumption that action execution is urgent variants are finally discussed in which action execution is delayable in the sense that an enabled action can let time advance before starting its execution or only the execution of internal actions is urgent which is known as maximal progress

reactive turing machines we propose reactive turing machines rtms extending classical turing machines with a process theoretical notion of interaction and use it to define a notion of executable transition system we show that every computable transition system with a bounded branching degree is simulated modulo divergence preserving branching bisimilarity by an rtm and that every effective transition system is simulated modulo the variant of branching bisimilarity that does not require divergence preservation we conclude from these results that the parallel composition of communicating rtms can be simulated by a single rtm we prove that there exist universal rtms modulo branching bisimilarity but these essentially employ divergence to be able to simulate an rtm of arbitrary branching degree we also prove that modulo divergence preserving branching bisimilarity there are rtms that are universal up to their own branching degree we establish a correspondence between executability and finite definability in a simple process calculus finally we establish that rtms are at least as expressive as persistent turing machines

ifrowann imbalanced fuzzy rough ordered weighted average nearest neighbor classification imbalanced classification deals with learning from data with a disproportional number of samples in its classes traditional classifiers exhibit poor behavior when facing this kind of data because they do not take into account the imbalanced class distribution four main kinds of solutions exist to solve this problem modifying the data distribution modifying the learning algorithm for considering the imbalance representation including the use of costs for data samples and ensemble methods in this paper we adopt the second type of solution and introduce a classification algorithm for imbalanced data that uses fuzzy rough set theory and ordered weighted average aggregation the proposal considers different strategies to build a weight vector to take into account data imbalance our methods are validated by an extensive experimental study showing statistically better results than 13 other state of the art methods

operational semantics for petri net components we propose a calculus for marked labelled nets components with places and transitions as atoms and merge addition fusion and relabelling as operators the operators are defined using graph based transformations each net can be represented by a term next we define both a step semantics for nets and a plotkin style sos semantics for net terms and show their equivalence in the semantics both state oriented and event oriented properties of components can be expressed we give a few rules for reducing components to smaller equivalent ones