Valentino Crespi

University of Southern California | USC · Information Sciences Institute

Recent improvements in the performance of state-of-the-art (SOTA) methods for Graph Representational Learning (GRL) have come at the cost of significant computational resource requirements for training, e.g., for calculating gradients via backprop over many data epochs. Meanwhile, Singular Value Decomposition (SVD) can find closed-form solutions to...

Computer security has been plagued by increasing formidable, dynamic, hard-to-detect, hard-to-predict, and hard-to-characterize hacking techniques. Such techniques are very often deployed in self-propagating worms capable of automatically infecting vulnerable computer systems and then building large bot networks, which are then used to launch coord...

Magnetic resonance imaging (MRI) has a potential for early diagnosis of individuals at risk for developing Alzheimer's disease (AD). Cognitive performance in healthy elderly people and in those with mild cognitive impairment (MCI) has been associated with measures of cortical gyrification [1] and thickness (CT) [2], yet the extent to which sulcal m...

Graph Representation Learning (GRL) has been advancing at an unprecedented rate. However, many results rely on careful design and tuning of architectures, objectives, and training schemes. We propose efficient GRL methods that optimize convexified objectives with known closed form solutions. Guaranteed convergence to a global optimum releases pract...

Our Multi-INT Data Association Tool (MIDAT) learns patterns of life (POL) of a geographical area from video analyst observations called out in textual reporting. Typical approaches to learning POLs from video make use of computer vision algorithms to extract locations in space and time of various activities. Such approaches are subject to the detec...

This paper develops techniques for attacking and defending behavioral anomaly detection methods commonly used in network traffic analysis and covert channels. The main new result is our demonstration of how to use a behavior's or process' k-order statistics to build a stochastic process that has the same k-order stationary statistics but possesses...

The Baum-Welsh algorithm together with its derivatives and variations has been the main technique for learning Hidden Markov Models (HMM) from observational data. We present an HMM learning algorithm based on the non-negative matrix factorization (NMF) of higher order Markovian statistics that is structurally different from the Baum-Welsh and its a...

In this paper we present methods for attacking and defending $k$-gram statistical analysis techniques that are used, for example, in network traffic analysis and covert channel detection. The main new result is our demonstration of how to use a behavior's or process' $k$-order statistics to build a stochastic process that has those same $k$-order s...

Traditionally, two alternative design approaches have been available to engineers: top-down and bottom-up. In the top-down approach, the design process starts with specifying the global system state and assuming that each component has global knowledge of the system, as in a centralized approach. The solution is then decentralized by replacing glob...

In a multistage interconnection network (MIN) the calculation of the number of permutations of the input terminals into the output terminals is a classic difficult problem. In this paper, we introduce an innovative technique based on Colored Petri Nets (known as CP-nets or CPNs) that will allow us to analyze the permutation capability of arbitrary...

The concept of trackability is intimately related to the establishment of optimal trade-offs between the nosiness of the environment, due to poor sensing, and the randomness of the kinematics of the phenomena being examined, due to poor knowledge of their behaviors. Classically, a sensor system receives low level data in the form of numerical or an...

We have developed a general framework, called a Process Query System (PQS), that serves as a foundation for formulating tracking problems, implementing software solutions to tracking problems and understanding theoretical issues related to tracking in specific scenarios. The PQS framework posits that an environment consists of multiple dynamical pr...

Given a multistage interconnection network (MIN) the calculation of the number of permutations of its input terminals into its output terminals is a classical difficult problem. In this paper, we introduce a novel technique to analyze the permutation capability of a MIN based on colored Petri nets (CP-nets or CPNs). We show how to verify whether a...

Hidden Markov models (HMMs) are currently employed in a wide variety of applications, including speech recognition, target tracking, and protein sequence analysis. The Viterbi algorithm is perhaps the best known method for tracking the hidden states of a process from a sequence of observations. An important problem when tracking a process with an H...

This paper presents an automated decentralized surveillance system for the problem of tracking multiple mobile ground targets with no signature in a bounded area. The system consists of unmanned aerial vehicles (UAVs) and unattended fixed ground sensors (UGSs) with limited communication and detection range that are deployed in the area of interest....

In this paper we describe metrics related to the quantification of situational awareness of surveillance systems based on sensor networks. Our work emphasizes the necessity for the sensor system to be able to track processes that evolve in general stochastically and may even be driven by intelligence. The result is a hierarchical model for surveill...

Not Available

Traditionally, top-down and bottom-up design approaches have competed with each other in Algorithmics and Software Engineering. In the top-down approach, design process starts with specifying the global system state and assuming that each component has global knowledge of the system, as in a centralized approach. The solution is then decentralized...

Process Query Systems (PQS) are a new kind of information retrieval technology in which user queries are expressed as process descriptions. The goal of a PQS is to detect the processes using a datastream or database of events that are correlated with the processes' states. This is in contrast with most traditional database query processing, informa...

In this paper, we investigate the link between the rate at which events are observed by a monitoring system and the ability of the system to effectively perform its tracking and surveillance tasks. In general, higher sampling rates provide better performance, but they also require more resources, both computationally and from the sensing infrastruc...

This paper presents a fully automated and decentralized surveillance system for the problem of detecting and possibly tracking mobile unknown ground vehicles in a bounded area. The system consists ideally of unmanned aerial vehicles (UAVs) and unattended fixed sensors with limited communication and detection range that are deployed in the area of i...

The Lovász theta function has attracted much attention for its connection with diverse issues such as communicating without errors and computing large cliques in graphs. Indeed, this function enjoys the remarkable property of being computable in polynomial time despite being sandwiched between clique and chromatic numbers, two well-known, hard to c...

We define a framework for what we call potential- based computing and show how it may be applied to action- motion applications in general and dynamic games in particular. We also describe how the framework lends itself to various forms of evolutionary computing.

In this paper we examine the role of very simple and noisy sensors for the tracking problem. We propose a binary sensor model, where each sensor's value is converted reliably to one bit of information only: whether the object is moving toward the sensor or away from the sensor. We show that a network of binary sensors has geometric properties that...

In this paper we investigate a problem arising in decentralized registration of sensors. The application we consider involves a heterogeneous collection of sensors - some sensors have on-board global positioning system (GPS) capabilities while others do not. All sensors have wireless communications capability but the wireless communication has limi...

Many surveillance and sensing applications involve the detection of dynamic processes. Examples include battle eld situation awareness (where the processes are vehicles and troop movements), computer and network security (where the processes are worms and other types of attacks), and homeland security (where processes are terrorist nancing, plannin...

This paper describes a distributed algorithm for coordinating the ow of a mass of vehicles approaching a highway exit or a tollbooth. We provide the problem formulation, a general methodology for distributed control and an instantiation of this methodology to the coordinated ow problem. We analyze our algorithm and provide experimental data.

this paper we investigate problems of target surveillance with the aim of building a general framework for the evaluation of the performance of a system of autonomous agents. To this purpose we propose a class of semi-distributed stochastic navigation algorithms, that drive swarms of autonomous scouts to the surveillance of grounded targets, and we...

Abstract The Lov asz theta function (G) of a graph G has attracted a lot of attention for its connection with diverse issues, such as communicating without errors and computing large cliques in graphs. Indeed this function enjoys the remarkable property of being computable in polynomial time, despite being sandwitched between clique and chromatic n...

In this article, we formalize the concept of tracking in a sensor network and develop a quantitative theory of trackability of weak models that investigates the rate of growth of the number of consistent tracks given a temporal sequence of observations made by the sensor network. The phenomenon being tracked is modelled by a nondeterministic finite...

The Lovasz theta function has attracted a lot of attention for its connection with diverse issues, such as communicating without errors and computing large cliques in graphs. Indeed this function enjoys the remarkable property of being computable in polynomial time, despite being sandwitched between clique and chromatic number, two well known hard...

This report summarizes our preliminary eorts at applying the methodology and techniques of agent-based systems engineering (ABSE) to the problem of designing and operating Intelligent Roads and Vehicles Systems (IRVS). First, we briey summarize the key elements of both agent-based systems engineering and IRVS. We then show how the taxonomy of ABSE...

We consider control problems that arise in the context of the IRVS. Speci cally, we study the dynamics of systems of fully autonomous agents that are expected to optimize a global potential function of which they have only partial knowledge. Our ultimate goal is to characterize mathematically the global performance of agent-based systems in which t...

Describes a distributed algorithm for coordinating the flow of a mass of vehicles approaching a highway exit or a tollbooth. We provide the problem formulation, a general methodology for distributed control and an instantiation of this methodology to the coordinated flow problem. We analyze our algorithm and provide experimental data

We obtain convenient expressions and/or efficient algorithms for the permanent of certain very sparse (0, 1) Toeplitz matrices. The classes of matrices considered here include some nontrivial examples of circulants to which none of the previous approaches could be successfully applied.

The theta function of a graph, also known as the Lovasz number, has the remarkable property of being computable in polynomial time, despite being sandwiched" between two hard to compute integers, i.e., clique and chromatic number. Very little is known about the explicit value of the theta function for special classes of graphs. In this paper we pro...

In this paper we address the problem of computing the permanent of (0; 1) -circulant matrices. We investigate structural properties of circulant matrices, showing that (i) if they are dense enough, then they contain large arbitrary submatrices, and, (ii) if they are very sparse, then they are not too "far" from convertible matrices. Building upon (...

The theta function of a graph, also known as the Lovász number, has the remarkable property of being computable in polynomial time, despite being "sandwiched" between two hard to compute integers, i.e., clique and chromatic number. Very little is known about the explicit value of the theta function for special classes of graphs. In this paper we pr...

this paper we obtain convenient expressions and/or efficient algorithms for the permanent of certain very sparse (0; 1) Toeplitz matrices. The classes of matrices considered here include some nontrivial examples of circulants to which none of the previous approaches could be successfully applied.

We take advantage of the special structure of computations in Z2 to develop algorithms for the computation of Groebner bases and of the Hilbert function in the Boolean setting. Natural sources of applications for our algorithms are the counting problems. We focus, as a case study, on the computation of the permanent. To this regard, one good featur...

Among the various proposals for an ‘Algebraic Specification of Concurrency’ [1], OBJSA Nets [3] are a class of algebraic high-level nets which combine Superposed Automata (SA) nets, a modular class of Petri nets, and the algebraic specification language OBJ. OBJS A Nets together with their support environment ONE (OBJSA Net Environment), constitute...