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Safe Compositional Network Sketches: The Formal Framework
, 2009
"... NetSketch is a tool for the specification of constrained-flow applications and the certification of desirable safety properties imposed thereon. NetSketch is conceived to assist system integrators in two types of activities: modeling and design. As a modeling tool, it enables the abstraction of an e ..."
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Cited by 19 (18 self)
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NetSketch is a tool for the specification of constrained-flow applications and the certification of desirable safety properties imposed thereon. NetSketch is conceived to assist system integrators in two types of activities: modeling and design. As a modeling tool, it enables the abstraction of an existing system while retaining sufficient information about it to carry out future analysis of safety properties. As a design tool, NetSketch enables the exploration of alternative safe designs as well as the identification of minimal requirements for outsourced subsystems. NetSketch embodies a lightweight formal verification philosophy, whereby the power (but not the heavy machinery) of a rigorous formalism is made accessible to users via a friendly interface. NetSketch does so by exposing tradeoffs between exactness of analysis and scalability, and by combining traditional whole-system analysis with a more flexible compositional analysis. The compositional analysis is based on a strongly-typed Domain-Specific Language (DSL) for describing and reasoning about constrained-flow networks at various levels of sketchiness along with invariants that need to be enforced thereupon. In this paper, we define the formal system underlying the operation of NetSketch, in particular the DSL behind NetSketch’s user-interface when used in “sketch mode”, and prove its soundness relative to appropriately-defined notions of validity. In a companion paper [6], we overview NetSketch, highlight its salient features, and illustrate how it could be used in two applications: the management/shaping of traffic flows in a vehicular network (as a proxy for CPS applications) and in a streaming media network (as a proxy for Internet applications). 1
Formal Verification of SLA Transformations
"... Abstract—Desirable application performance is typically guaranteed through the use of Service Level Agreements (SLAs) that specify fixed fractions of resource capacities that must be allocated for unencumbered use by the application. The mapping between what constitutes desirable performance and SLA ..."
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Cited by 4 (4 self)
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Abstract—Desirable application performance is typically guaranteed through the use of Service Level Agreements (SLAs) that specify fixed fractions of resource capacities that must be allocated for unencumbered use by the application. The mapping between what constitutes desirable performance and SLAs is not unique: multiple SLA expressions might be functionally equivalent. Having the flexibility to transform SLAs from one form to another in a manner that is provably safe would enable hosting solutions to achieve significant efficiencies. This paper demonstrates the promise of such an approach by proposing a type-theoretic framework for the representation and safe transformation of SLAs. Based on that framework, the paper describes a methodical approach for the inference of efficient and safe mappings of periodic, real-time tasks to the physical and virtual hosts that constitute a hierarchical scheduler. Extensive experimental results support the conclusion that the flexibility afforded by safe SLA transformations has the potential to yield significant savings. I.
Accessible Integrated Formal Reasoning Environments in Classroom Instruction of Mathematics
"... Computer science researchers in the programming languages and formal verification communities, among others, have produced a variety of automated assistance and verification tools and techniques for formal reasoning: parsers, evaluators, proof-authoring systems, software verification systems, intera ..."
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Cited by 1 (1 self)
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Computer science researchers in the programming languages and formal verification communities, among others, have produced a variety of automated assistance and verification tools and techniques for formal reasoning: parsers, evaluators, proof-authoring systems, software verification systems, interactive theorem provers, model-checkers, static analysis methods, and so on. While there have been notable successes in utilizing
User-friendly Support for Common Mathematical Concepts in a Lightweight Verifier (Discussion Paper) ∗
"... Machine verification of formal arguments can only increase our confidence in the correctness of those arguments, but the costs of employing machine verification still outweigh the benefits for some common kinds of formal reasoning activities. As a result, usability is becoming increasingly important ..."
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Machine verification of formal arguments can only increase our confidence in the correctness of those arguments, but the costs of employing machine verification still outweigh the benefits for some common kinds of formal reasoning activities. As a result, usability is becoming increasingly important in the design of formal verification tools. We describe the AARTIFACT lightweight verification system, designed for processing formal arguments involving basic, ubiquitous mathematical concepts. The system is a prototype for investigating potential techniques for improving the usability of formal verification systems. It leverages techniques drawn both from existing work and from our own efforts. In addition to a parser for a familiar concrete syntax and a mechanism for automated syntax lookup, the system integrates (1) a basic logical inference algorithm, (2) a database of propositions governing common mathematical concepts, and (3) a data structure that computes congruence closures of expressions involving relations found in this database. Together, these components allow the system to better accommodate the expectations of users interested in verifying formal arguments involving algebraic and logical manipulations of numbers, sets, vectors, and related operators and predicates. We demonstrate the reasonable performance of this system on typical formal arguments and briefly discuss how the system’s design contributed to its usability in two case studies. 1
Ontology Support for a Lightweight Formal Verification System ∗
"... The usability of verification systems is becoming increasingly important, and the effective integration of ontologies of formal facts (definitions, propositions, and syntactic idioms) into machine verification systems will likely play a role in improving the usability of such systems. The AARTI-FACT ..."
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The usability of verification systems is becoming increasingly important, and the effective integration of ontologies of formal facts (definitions, propositions, and syntactic idioms) into machine verification systems will likely play a role in improving the usability of such systems. The AARTI-FACT lightweight verification system utilizes an ontology of formal propositions in order to support lightweight verification of formal arguments that involve common mathematical concepts. The ontology is stored within a relational database, and can be assembled and extended using a simple web interface by contributors who are domain experts. The database can be compiled into two separate components of the AARTIFACT system: a verifier component that computes congruence closures of expressions containing relations and predicates found in the ontology, and a JavaScript application that interactively presents to users information about the constants, operators, relations, predicates, syntactic constructs, and idioms found in the ontology (and, thus, supported by the verifier). In this way, the database serves to improve both the verification system’s capacity to infer implicit applications of logical propositions within a user’s formal argument, and to inform users in a context-aware and structured manner of the verification system’s capabilities and limitations. 1
Abstract
"... NetSketch is a tool for the specification of constrained-flow networks (CFNs) and the certification of desirable safety properties imposed thereon, conceived to assist system integrators in modeling and design. It provides compositional analysis capabilities based on a strongly-typed domain-specific ..."
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NetSketch is a tool for the specification of constrained-flow networks (CFNs) and the certification of desirable safety properties imposed thereon, conceived to assist system integrators in modeling and design. It provides compositional analysis capabilities based on a strongly-typed domain-specific language (DSL) for describing and reasoning about CFNs and relevant invariants. Users can model or design individual network components and perform manual or automated whole-system analysis of the properties thereof. Users can also assemble many instances of these components into larger networks, relying on NetSketch’s less precise but more tractable compositional analysis capabilities. This ability to trade “precision of analysis ” for “feasibility of analysis ” according to available resources is among the novel features of NetSketch. In earlier work we illustrated how NetSketch is applied to actual domains [6], and provided a formal definition of its underlying formalism [7]. While the NetSketch DSL provides automatic compositional analysis capabilities for modeling and designing entire networks, users may need to employ a wider variety of tools and techniques when modeling and designing individual network components. These can include common tools for reasoning about systems of constraints of various classes (such as linear constraints, quadratic constraints, and so on), as well as logical systems and ontologies that deal with concepts relevant to
