Vineet Gupta - Academia.edu (original) (raw)

Papers by Vineet Gupta

A Chu space is a binary relation between two sets. In this thesis we show that Chuspaces form a n... more A Chu space is a binary relation between two sets. In this thesis we show that Chuspaces form a non-interleaving model of concurrency which extends event structureswhile endowing them with an algebraic structure whose natural logic is linear logic.We provide several equivalent definitions of Chu spaces, including two pictorialrepresentations. Chu spaces represent processes as automata or schedules, and Chuduality gives a simple way of converting between schedules and automata. We showthat ...

We consider a class of Kripke Structures in which the atomic propositions are events. This enable... more We consider a class of Kripke Structures in which the atomic propositions are events. This enables us to represent worlds as sets of events and the transition and satisfaction relations of Kripke structures as the subset and membership relations on sets. We use this class, called event Kripke structures, to model concurrency. The obvious semantics for these structures is a true concurrency semantics. We show how several aspects of concurrency can be easily de ned, and in addition get distinctions between causality and enabling, and choice and nondeterminism. We de ne a duality for event Kripke structures, and show how this duality enables us to convert between imperative and declarative views of programs, by treating states and events on the same footing. We provide pictorial representations of both these views, each encoding all the information to convert to the other.

This paper reports on the findings of an on-going project to investigate techniques to diagnose c... more This paper reports on the findings of an on-going project to investigate techniques to diagnose complex dynamical systems that are modeled as hybrid systems. In particular, we examine continuous systems with embedded supervisory controllers which experience abrupt, partial or full failure of component devices. The problem we address is: given a hybrid model of system behavior, a history of executed controller actions, and a history of observations, including an observation of behavior that is aberrant relative to the model of expected behavior, determine what fault occurred to have caused the aberrant behavior. Determining a diagnosis can be cast as a search problem to find the most likely model for the data. Unfortunately, the search space is extremely large. To reduce search space size and to identify an initial set of candidate diagnoses, we propose to exploit techniques originally applied to qualitative diagnosis of continuous systems. We refine these diagnoses using parameter estimation and model fitting techniques. As a motivating case study, we have examined the problem of diagnosing NASA's Sprint AERCam, a small spherical robotic camera unit with 12 thrusters that enable both linear and rotational motion.

Proceedings of the Eighth ACM International Conference on Web Search and Data Mining - WSDM '15, 2015

We present a user modeling system that serves as the foundation of a personal assistant. The syst... more We present a user modeling system that serves as the foundation of a personal assistant. The system ingests web search history for signed-in users, and identifies coherent contexts that correspond to tasks, interests, and habits. Unlike past work which focused on either in-session tasks or tasks over a few days, we look at several months of history in order to identify not just short-term tasks, but also long-term interests and habits. The features we use for identifying coherent contexts yield substantially higher precision and recall than past work. We also present an algorithm for identifying contexts that is 8 to 30 times faster than previous algorithms. The user modeling system has been deployed in production. It runs over hundreds of millions of users, and updates the models with a 10-minute latency. The contexts identified by the system serve as the foundation for generating recommendations in Google Now.

This paper presents a model for the Sprint AERCam, a beachball sized robotic camera that floats a... more This paper presents a model for the Sprint AERCam, a beachball sized robotic camera that floats around in the cargo bay of the Space Shuttle, allowing the astronauts and ground mission control to have an additional view of the task they are trying to accomplish. It has a self contained propulsion system, giving it the capability to maneuver with six degrees of freedom. We present a model for the AERCam written in Hybrid cc, an extension of cc programming for modeling continuous/discrete systems. We modeled both the dynamics and control of the AERCam in Hybrid cc, and interfaced this model with an animation interface which allows a user to interact with the model in real-time.

This paper explores Lhc expressive power of Lhc tcc paradigm. The origin ofLhc work in Lhc inLcgr... more This paper explores Lhc expressive power of Lhc tcc paradigm. The origin ofLhc work in Lhc inLcgraLion of synchronous and consLrainL programming is described.The basic conceptual and maLhcmaLical framework developed in Lhcspirk of Lhc model-based approach characLcrisLic of LhcorcLical compuLcr scienceis reviewed. Wc show LhaL a range of consLrucLs for expressing LimcouLs,prccmpLion and oLhcr complicaLcd paLLcrns of Lcmporal acLivky arc

Markov processes with continuous state spaces arise in the analysis of stochastic physical system... more Markov processes with continuous state spaces arise in the analysis of stochastic physical systems or stochastic hybrid systems. The standard logical and algorithmic tools for reasoning about discrete ( nite-state) systems are, of course, inadequate for reasoning about such systems. In this work we develop three related ideas for making such reasoning principles applicable to continuous systems.

Information and Computation, 2010

We investigate weak bisimulation of probabilistic systems in the presence of nondeterminism, i.e.... more We investigate weak bisimulation of probabilistic systems in the presence of nondeterminism, i.e. labelled concurrent Markov chains (LCMC) with silent transitions. We develop an approach based on allowing convex combinations of computations, similar to Segala and Lynch's use of randomized schedulers.

Many of today's electro-mechanical devices exhibit both continuous and discrete behavior .

We extend the model of SJG94b] to express strong timeouts (and pre-emption): if an event A does n... more We extend the model of SJG94b] to express strong timeouts (and pre-emption): if an event A does not happen through time t, cause event B to happen at time t. Such constructs arise naturally in practice (e.g. in modeling transistors) and are supported in languages such as Esterel (through instantaneous watchdogs) and Lustre (through the \current" operator).

We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is d... more We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is declarative, with programs being understood as logical formulas that place constraints upon the temporal evolution of a system. We show the expressiveness of our language by presenting several examples, including a model for the paperpath of a photocopier. We describe an interpreter for our language, and provide traces for some of the example programs.

We present a compositional model of paper transportation in a photocopier that is meant to suppor... more We present a compositional model of paper transportation in a photocopier that is meant to support di erent problem solving tasks like simulation and diagnosis, and to be applicable to a variety of con gurations. Therefore, we try to avoid making hard-wired implicit assumptions about design principles and possible scenarios. In order to simplify our analysis, the model abstracts away from the physical forces and reasons only about velocities. Nonetheless, it succeeds in determining essential features of the motion of the sheet of paper like buckling and tearing. The framework provided is quite generic and can be used as a starting point for developing models of other transportation domains.

We present a compositional steady-state model of paper transportation in a photocopier that is me... more We present a compositional steady-state model of paper transportation in a photocopier that is meant to support different problem solving tasks like simulation and diagnosis, and to be applicable to a variety of configurations. The model avoids making hard-wired implicit assumptions about design principles and possible scenarios, though second-order effects such as the effect of gravity, and non-zero sheet mass are ignored.

Labelled Markov processes are probabilistic versions of labelled transition systems. In general, ... more Labelled Markov processes are probabilistic versions of labelled transition systems. In general, the state space of a labelled Markov process may be a continuum. In this paper, we study approximation techniques for continuous-state labelled Markov processes. We show that the collection of labelled Markov processes carries a Polish-space structure with a countable basis given by finite-state Markov chains with rational probabilities; thus permitting the approximation of quantitative observations (e.g. an integral of a continuous function) of a continuous-state labelled Markov process by the observations on nite-state Markov chains. The primary technical tools that we develop to reach these results are A variant of a finite-model theorem for the modal logic used to characterize bisimulation, and an isomorphism between the poset of Markov processes (ordered by simulation) with the !-continuous dcpo Proc (defined as the solution of the recursive domain equation Proc = Q L P Pr (Proc)). ...

A Chu space is a binary relation between two sets. In this thesis we show that Chuspaces form a n... more A Chu space is a binary relation between two sets. In this thesis we show that Chuspaces form a non-interleaving model of concurrency which extends event structureswhile endowing them with an algebraic structure whose natural logic is linear logic.We provide several equivalent definitions of Chu spaces, including two pictorialrepresentations. Chu spaces represent processes as automata or schedules, and Chuduality gives a simple way of converting between schedules and automata. We showthat ...

We consider a class of Kripke Structures in which the atomic propositions are events. This enable... more We consider a class of Kripke Structures in which the atomic propositions are events. This enables us to represent worlds as sets of events and the transition and satisfaction relations of Kripke structures as the subset and membership relations on sets. We use this class, called event Kripke structures, to model concurrency. The obvious semantics for these structures is a true concurrency semantics. We show how several aspects of concurrency can be easily de ned, and in addition get distinctions between causality and enabling, and choice and nondeterminism. We de ne a duality for event Kripke structures, and show how this duality enables us to convert between imperative and declarative views of programs, by treating states and events on the same footing. We provide pictorial representations of both these views, each encoding all the information to convert to the other.

This paper reports on the findings of an on-going project to investigate techniques to diagnose c... more This paper reports on the findings of an on-going project to investigate techniques to diagnose complex dynamical systems that are modeled as hybrid systems. In particular, we examine continuous systems with embedded supervisory controllers which experience abrupt, partial or full failure of component devices. The problem we address is: given a hybrid model of system behavior, a history of executed controller actions, and a history of observations, including an observation of behavior that is aberrant relative to the model of expected behavior, determine what fault occurred to have caused the aberrant behavior. Determining a diagnosis can be cast as a search problem to find the most likely model for the data. Unfortunately, the search space is extremely large. To reduce search space size and to identify an initial set of candidate diagnoses, we propose to exploit techniques originally applied to qualitative diagnosis of continuous systems. We refine these diagnoses using parameter estimation and model fitting techniques. As a motivating case study, we have examined the problem of diagnosing NASA's Sprint AERCam, a small spherical robotic camera unit with 12 thrusters that enable both linear and rotational motion.

Proceedings of the Eighth ACM International Conference on Web Search and Data Mining - WSDM '15, 2015

We present a user modeling system that serves as the foundation of a personal assistant. The syst... more We present a user modeling system that serves as the foundation of a personal assistant. The system ingests web search history for signed-in users, and identifies coherent contexts that correspond to tasks, interests, and habits. Unlike past work which focused on either in-session tasks or tasks over a few days, we look at several months of history in order to identify not just short-term tasks, but also long-term interests and habits. The features we use for identifying coherent contexts yield substantially higher precision and recall than past work. We also present an algorithm for identifying contexts that is 8 to 30 times faster than previous algorithms. The user modeling system has been deployed in production. It runs over hundreds of millions of users, and updates the models with a 10-minute latency. The contexts identified by the system serve as the foundation for generating recommendations in Google Now.

This paper presents a model for the Sprint AERCam, a beachball sized robotic camera that floats a... more This paper presents a model for the Sprint AERCam, a beachball sized robotic camera that floats around in the cargo bay of the Space Shuttle, allowing the astronauts and ground mission control to have an additional view of the task they are trying to accomplish. It has a self contained propulsion system, giving it the capability to maneuver with six degrees of freedom. We present a model for the AERCam written in Hybrid cc, an extension of cc programming for modeling continuous/discrete systems. We modeled both the dynamics and control of the AERCam in Hybrid cc, and interfaced this model with an animation interface which allows a user to interact with the model in real-time.

This paper explores Lhc expressive power of Lhc tcc paradigm. The origin ofLhc work in Lhc inLcgr... more This paper explores Lhc expressive power of Lhc tcc paradigm. The origin ofLhc work in Lhc inLcgraLion of synchronous and consLrainL programming is described.The basic conceptual and maLhcmaLical framework developed in Lhcspirk of Lhc model-based approach characLcrisLic of LhcorcLical compuLcr scienceis reviewed. Wc show LhaL a range of consLrucLs for expressing LimcouLs,prccmpLion and oLhcr complicaLcd paLLcrns of Lcmporal acLivky arc

Markov processes with continuous state spaces arise in the analysis of stochastic physical system... more Markov processes with continuous state spaces arise in the analysis of stochastic physical systems or stochastic hybrid systems. The standard logical and algorithmic tools for reasoning about discrete ( nite-state) systems are, of course, inadequate for reasoning about such systems. In this work we develop three related ideas for making such reasoning principles applicable to continuous systems.

Information and Computation, 2010

We investigate weak bisimulation of probabilistic systems in the presence of nondeterminism, i.e.... more We investigate weak bisimulation of probabilistic systems in the presence of nondeterminism, i.e. labelled concurrent Markov chains (LCMC) with silent transitions. We develop an approach based on allowing convex combinations of computations, similar to Segala and Lynch's use of randomized schedulers.

Many of today's electro-mechanical devices exhibit both continuous and discrete behavior .

We extend the model of SJG94b] to express strong timeouts (and pre-emption): if an event A does n... more We extend the model of SJG94b] to express strong timeouts (and pre-emption): if an event A does not happen through time t, cause event B to happen at time t. Such constructs arise naturally in practice (e.g. in modeling transistors) and are supported in languages such as Esterel (through instantaneous watchdogs) and Lustre (through the \current" operator).

We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is d... more We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is declarative, with programs being understood as logical formulas that place constraints upon the temporal evolution of a system. We show the expressiveness of our language by presenting several examples, including a model for the paperpath of a photocopier. We describe an interpreter for our language, and provide traces for some of the example programs.

We present a compositional model of paper transportation in a photocopier that is meant to suppor... more We present a compositional model of paper transportation in a photocopier that is meant to support di erent problem solving tasks like simulation and diagnosis, and to be applicable to a variety of con gurations. Therefore, we try to avoid making hard-wired implicit assumptions about design principles and possible scenarios. In order to simplify our analysis, the model abstracts away from the physical forces and reasons only about velocities. Nonetheless, it succeeds in determining essential features of the motion of the sheet of paper like buckling and tearing. The framework provided is quite generic and can be used as a starting point for developing models of other transportation domains.

We present a compositional steady-state model of paper transportation in a photocopier that is me... more We present a compositional steady-state model of paper transportation in a photocopier that is meant to support different problem solving tasks like simulation and diagnosis, and to be applicable to a variety of configurations. The model avoids making hard-wired implicit assumptions about design principles and possible scenarios, though second-order effects such as the effect of gravity, and non-zero sheet mass are ignored.

Labelled Markov processes are probabilistic versions of labelled transition systems. In general, ... more Labelled Markov processes are probabilistic versions of labelled transition systems. In general, the state space of a labelled Markov process may be a continuum. In this paper, we study approximation techniques for continuous-state labelled Markov processes. We show that the collection of labelled Markov processes carries a Polish-space structure with a countable basis given by finite-state Markov chains with rational probabilities; thus permitting the approximation of quantitative observations (e.g. an integral of a continuous function) of a continuous-state labelled Markov process by the observations on nite-state Markov chains. The primary technical tools that we develop to reach these results are A variant of a finite-model theorem for the modal logic used to characterize bisimulation, and an isomorphism between the poset of Markov processes (ordered by simulation) with the !-continuous dcpo Proc (defined as the solution of the recursive domain equation Proc = Q L P Pr (Proc)). ...