225,906 research outputs found
A Logic of Blockchain Updates
Blockchains are distributed data structures that are used to achieve
consensus in systems for cryptocurrencies (like Bitcoin) or smart contracts
(like Ethereum). Although blockchains gained a lot of popularity recently,
there is no logic-based model for blockchains available. We introduce BCL, a
dynamic logic to reason about blockchain updates, and show that BCL is sound
and complete with respect to a simple blockchain model
Specifying Reusable Components
Reusable software components need expressive specifications. This paper
outlines a rigorous foundation to model-based contracts, a method to equip
classes with strong contracts that support accurate design, implementation, and
formal verification of reusable components. Model-based contracts
conservatively extend the classic Design by Contract with a notion of model,
which underpins the precise definitions of such concepts as abstract
equivalence and specification completeness. Experiments applying model-based
contracts to libraries of data structures suggest that the method enables
accurate specification of practical software
Orchestrated Session Compliance
We investigate the notion of orchestrated compliance for client/server
interactions in the context of session contracts. Devising the notion of
orchestrator in such a context makes it possible to have orchestrators with
unbounded buffering capabilities and at the same time to guarantee any message
from the client to be eventually delivered by the orchestrator to the server,
while preventing the server from sending messages which are kept indefinitely
inside the orchestrator. The compliance relation is shown to be decidable by
means of 1) a procedure synthesising the orchestrators, if any, making a client
compliant with a server, and 2) a procedure for deciding whether an
orchestrator behaves in a proper way as mentioned before.Comment: In Proceedings ICE 2015, arXiv:1508.0459
Oceanographic and underwater acoustics research : conducted during the period 1 November 1960 - 30 April 1961
Digital computing techniques have been used in special computing applications in underwater acoustics at WHOI for many years, but recently we have commenced intensive application of digital data handling and computing facilities to a variety of computing, data storage, and data handling problems. Progress in these applications is described under Acoustic Instrumentation below.
Some bathymetric studies carried out recently under another contract have shown that even very narrow-beam, single-beam echo sounders simply cannot provide reliable depth sounding information where the topography is complex. In this work we have been experimenting with the inverted echo sounder, discussed below, originally developed to measure depth of the sound velocimeter. The inverted echo sounder is lowered to a position within a few feet of the bottom. The total acoustic travel time from surface to bottom may be read as the sum of the travel times from the instrument to the bottom and surface . True depth is then computed in the usual way with appropriate s cnmd velocity data. In its present form the inverted echo sounder is suitable for mapping ~mall areas~ a few square miles, provided there is a suitable means of positioning the instrument. We have experimented with radio-acoustic navigation, and intend to experiment with vertical triangulation from the suspending ship as well.
Steady demands for new, modified, and improved instrumentation have been responded to in echo sounding, seismic profiling, and spectrum analysis, as detailed below.Undersea Warfare Branch Office of Naval Research Under Contracts Nonr-1367(00)NR261-102 and Nonr-2129(00)NR261-10
Preliminary Results Towards Contract Monitorability
This paper discusses preliminary investigations on the monitorability of
contracts for web service descriptions. There are settings where servers do not
guarantee statically whether they satisfy some specified contract, which forces
the client (i.e., the entity interacting with the server) to perform dynamic
checks. This scenario may be viewed as an instance of Runtime Verification,
where a pertinent question is whether contracts can be monitored for adequately
at runtime, otherwise stated as the monitorability of contracts. We consider a
simple language of finitary contracts describing both clients and servers, and
develop a formal framework that describes server contract monitoring. We define
monitor properties that potentially contribute towards a comprehensive notion
of contract monitorability and show that our simple contract language satisfies
these properties.Comment: In Proceedings PrePost 2016, arXiv:1605.0809
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