Mabry Tyson

A security enforcement kernel for OpenFlow networks

Software-defined networks facilitate rapid and open innovation at the network control layer by providing a programmable network infrastructure for computing flow policies on demand. However, the dynamism of programmable networks also introduces new security challenges that demand innovative solutions. A critical challenge is efficient detection and reconciliation of potentially conflicting flow rules imposed by dynamic OpenFlow (OF) applications. To that end, we introduce FortNOX, a software extension that provides role-based authorization and security constraint enforcement for the NOX OpenFlow controller. FortNOX enables NOX to check flow rule contradictions in real time, and implements a novel analysis algorithm that is robust even in cases where an adversarial OF application attempts to strategically insert flow rules that would otherwise circumvent flow rules imposed by OF security applications. We demonstrate the utility of FortNOX through a prototype implementation and use it to examine performance and efficiency aspects of the proposed framework.

SRI International FASTUS system: MUC-6 test results and analysis

SRI International participated in the MUC-6 evaluation using the latest version of SRIs FASTUS system [1]. The FASTUS system was originally developed for participation in the MUC-4 evaluation [3] in 1992, and the performance of FASTUS in MUC-4 helped demonstrate the viability of finite state technologies in constrained natural-language understanding tasks. The system has undergone significant revision since MUC-4, and it is safe to say that the current system does not share a single line of code with the original. The fundamental ideas behind FASTUS, however, are retained in the current system: an architecture consisting of cascaded finite state transducers, each providing an additional level of analysis of the input, together with merging of the final results.

FASTUS: a system for extracting information from text

FASTUS is a (slightly permuted) acronym for Finite State Automaton Text Understanding System. It is a system for extracting information from free text in English (Japanese is under development), for entry into a database, and potentially for other applications. It works essentially as a set of cascaded, nondeterministic finite state automata.

SRI International: description of the FASTUS system used for MUC-4

FASTUS is a (slightly permuted) acronym for Finite State Automaton Text Understanding System. It is a system for extracting information from free text in English, and potentially other languages as well, for entry into a database, and potentially for other applications. It works essentially as a cascaded, nondeterministic finite state automaton.

Robust Processing of Real-World Natural-Language Texts

It is often assumed that when natural language processing meets the real world, the ideal of aiming for complete and correct interpretations has to be abandoned. However, our experience with TACITUS; especially in the MUC-3 evaluation, has shown that principled techniques for syntactic and pragmatic analysis can be bolstered with methods for achieving robustness. We describe three techniques for making syntactic analysis more robust-an agenda-based scheduling parser, a recovery technique for failed parses, and a new technique called terminal substring parsing. For pragmatics processing, we describe how the method of abductive inference is inherently robust, in that an interpretation is always possible, so that in the absence of the required world knowledge, performance degrades gracefully. Each of these techniques have been evaluated and the results of the evaluations are presented.

SRI's Tipster II Project

The principal barrier to the widespread use of information extraction technology is the difficulty in defining the patterns that represent ones information requirements. Much of the work that has been done on SRIs Tipster II project has been directed at overcoming this barrier. In this paper, after some background on the basic structure of the FASTUS system, we present some of these developments. Specifically, we discuss the declarative pattern specification language FastSpec, compile-time transformations, and adapting rules from examples. In addition, we have developed the basic capabilities of FASTUS. We describe our efforts in one are---coreference resolution. We are now experimenting with the use of FASTUS in improving document retrieval and this is also described.

TACITUS: a message understanding system

TACITUS is a general and domain-independent natural language processing system, used so far primarily for message processing. It performs a syntactic analysis of the sentences in the text, producing a logical form. Next, inferential pragmatics processing is applied to the logical form to solve problems of schema recognition, reference resolution, metonymy resolution, and the interpretation of vague predicates. An analysis component then produces the desired output for the application. TACITUS has been applied to several quite different domains, including naval equipment failure reports, naval operations reports, and terrorist reports.