About

Assaf Kfoury is a professor in the Department of Computer Science at Boston University, with a research focus on the interactions between Mathematical Logic and Computer Science. His interests include type theory, the lambda-calculus, static analysis, recursion theory, and the theory of program schemas, among other areas. Throughout his career, he has explored various facets of formal methods, automated proof systems, and the theoretical foundations of computer science, often producing tutorials, research reports, and seminar presentations that provide different perspectives on known material. Kfoury's teaching portfolio includes graduate-level courses on Formal Methods in CS, emphasizing SAT/SMT solvers, automated proof assistants, and temporal and modal logics. He has also taught courses on algorithm design, foundations of programming languages, lambda-calculus, computability theory, mathematical logic, and model theory. His approach to teaching involves developing his own lecture notes to stress concepts and their interdependence, aiming for clarity and transparency. His research extends beyond formal logic, engaging with graph theory, applied algorithms, system networking, and software development, often collaborating with colleagues and students on projects that intersect formal methods with practical system applications. Kfoury has contributed to the academic community through the creation of tutorials, research reports, and seminars, covering topics such as proof assistants, term-rewriting systems, and formal verification. His recent work includes reports on the role of mathematical logic in computer science, graph reassembling algorithms, and formal verification platforms for networked systems. He has a long-standing commitment to advancing the understanding of formal methods and their applications, and he actively supports various scientific and social organizations.

Research topics

• Computer science
• Programming language
• Mathematics
• Theoretical computer science
• Discrete mathematics

Selected publications

• Efficient reassembling of three-regular planar graphs

  Journal of Combinatorial Optimization · 2020-03-07

  preprintOpen access1st authorCorresponding
  PublisherOA PDFDOI

• MORPHOSYS: Efficient Colocation of QoS-Constrained Workloads in the\n Cloud

  arXiv (Cornell University) · 2019-12-01

  preprintOpen accessSenior author

  In hosting environments such as IaaS clouds, desirable application\nperformance is usually guaranteed through the use of Service Level Agreements\n(SLAs), which specify minimal fractions of resource capacities that must be\nallocated for use for proper operation. Arbitrary colocation of applications\nwith different SLAs on a single host may result in inefficient utilization of\nthe host's resources. In this paper, we propose that periodic resource\nallocation and consumption models be used for a more granular expression of\nSLAs. Our proposed SLA model has the salient feature that it exposes\nflexibilities that enable the IaaS provider to safelya transform SLAs from one\nform to another for the purpose of achieving more efficient colocation. Towards\nthat goal, we present MorphoSys: a framework for a service that allows the\nmanipulation of SLAs to enable efficient colocation of workloads. We present\nresults from extensive trace-driven simulations of colocated Video-on-Demand\nservers in a cloud setting. The results show that potentially-significant\nreduction in wasted resources (by as much as 60%) are possible using MorphoSys.\n

  PublisherOA PDFDOI

• Personal Reflections on the Role of Mathematical Logic in Computer Science

  Fundamenta Informaticae · 2019-10-18 · 4 citations

  article1st authorCorresponding

  This article traces in broad strokes the evolution of the intimate relationship between mathematical logic and computer science. The emphasis is on turning points in this relationship, i.e., moments when new directions of research were opened and new connections were established between the two fie lds. The article is not a comprehensive account and history of the relationship, but a personal perspective of a profoundly changed, and still changing, inter-dependence between two mainstays of the mathematical disciplines.

  PublisherDOI

• MORPHOSYS: Efficient Colocation of QoS-Constrained Workloads in the Cloud

  arXiv (Cornell University) · 2019-12-02

  preprintOpen accessSenior author

  In hosting environments such as IaaS clouds, desirable application performance is usually guaranteed through the use of Service Level Agreements (SLAs), which specify minimal fractions of resource capacities that must be allocated for use for proper operation. Arbitrary colocation of applications with different SLAs on a single host may result in inefficient utilization of the host's resources. In this paper, we propose that periodic resource allocation and consumption models be used for a more granular expression of SLAs. Our proposed SLA model has the salient feature that it exposes flexibilities that enable the IaaS provider to safelya transform SLAs from one form to another for the purpose of achieving more efficient colocation. Towards that goal, we present MorphoSys: a framework for a service that allows the manipulation of SLAs to enable efficient colocation of workloads. We present results from extensive trace-driven simulations of colocated Video-on-Demand servers in a cloud setting. The results show that potentially-significant reduction in wasted resources (by as much as 60%) are possible using MorphoSys.

  PublisherOA PDFDOI

• A Fixed-Parameter Linear-Time Algorithm to Compute Principal Typings of Planar Flow Networks

  arXiv (Cornell University) · 2018-07-18

  preprintOpen access1st authorCorresponding

  We present an alternative and simpler method for computing principal typings of flow networks. When limited to planar flow networks, the method can be made to run in fixed-parameter linear-time -- where the parameter not to be exceeded is what is called the edge-outerplanarity of the networks' underlying graphs.

  PublisherOA PDFDOI

• Mathematical Logic in Computer Science

  arXiv (Cornell University) · 2018-02-07 · 1 citations

  preprintOpen access1st authorCorresponding

  The article retraces major events and milestones in the mutual influences between mathematical logic and computer science since the 1950s.

  PublisherOA PDFDOI

• A Fixed-Parameter Linear-Time Algorithm to Compute Principal Typings of\n Planar Flow Networks

  arXiv (Cornell University) · 2018-07-18

  preprintOpen access1st authorCorresponding

  We present an alternative and simpler method for computing principal typings\nof flow networks. When limited to planar flow networks, the method can be made\nto run in fixed-parameter linear-time -- where the parameter not to be exceeded\nis what is called the edge-outerplanarity of the networks' underlying graphs.\n

  PublisherOA PDFDOI

• A Fixed-Parameter Linear-Time Algorithm for Maximum Flow in Planar Flow\n Networks

  arXiv (Cornell University) · 2018-07-11

  preprintOpen access1st authorCorresponding

  We pull together previously established graph-theoretical results to produce\nthe algorithm in the paper's title. The glue are three easy elementary lemmas.\n

  PublisherOA PDFDOI

• A Fixed-Parameter Linear-Time Algorithm for Maximum Flow in Planar Flow Networks

  OpenBU (Boston University) · 2018-07-11 · 1 citations

  preprintOpen access1st authorCorresponding

  We pull together previously established graph-theoretical results to produce the algorithm in the paper's title. The glue are three easy elementary lemmas.

  PublisherOA PDFDOI

• A Compositional Approach to Network Algorithms

  arXiv (Cornell University) · 2018-05-19 · 3 citations

  preprintOpen access1st authorCorresponding

  We present elements of a typing theory for flow networks, where "types", "typings", and "type inference" are formulated in terms of familiar notions from polyhedral analysis and convex optimization. Based on this typing theory, we develop an alternative approach to the design and analysis of network algorithms, which we illustrate by applying it to the max-flow problem in multiple-source, multiple-sink, capacited directed planar graphs.

  PublisherOA PDFDOI

Recent grants

• Genericity in Network Software: Using Type Systems and Formal Methods to Harness Diverse Theories and Calculi for Scalable and Safe Compositions of Network Services

  NSF · $400k · 2008–2012

Frequent coauthors

• Azer Bestavros

  36 shared

• Robert N. Moll

  University of Massachusetts Amherst

  25 shared

• Michael A. Arbib

  University of California, San Diego

  25 shared

• Jerzy Tiuryn

  University of Warsaw

  21 shared

• Paweł Urzyczyn

  University of Warsaw

  20 shared

• Andrei Lapets

  20 shared

• J. B. Wells

  12 shared

• Adam D. Bradley

  University of Ontario Institute of Technology

  11 shared

Education

• Ph.D.

  MIT