163 research outputs found
Timed Session Types
Timed session types formalise timed communication protocols between two
participants at the endpoints of a session. They feature a decidable compliance
relation, which generalises to the timed setting the progress-based compliance
between untimed session types. We show a sound and complete technique to decide
when a timed session type admits a compliant one. Then, we show how to
construct the most precise session type compliant with a given one, according
to the subtyping preorder induced by compliance. Decidability of subtyping
follows from these results
Contextual behavioural Metrics (Extended Version)
We introduce contextual behavioural metrics (CBMs) as a novel way of
measuring the discrepancy in behaviour between processes, taking into account
both quantitative aspects and contextual information. This way, process
distances by construction take the environment into account: two
(non-equivalent) processes may still exhibit very similar behaviour in some
contexts, e.g., when certain actions are never performed. We first show how
CBMs capture many well-known notions of equivalence and metric, including
Larsen's environmental parametrized bisimulation. We then study compositional
properties of CBMs with respect to some common process algebraic operators,
namely prefixing, restriction, non-deterministic sum, parallel composition and
replication.Comment: Extended version of a paper accepted for publication in proc. CONCUR
202
Contextual Behavioural Metrics
International audienceWe introduce contextual behavioural metrics (CBMs) as a novel way of measuring the discrepancy in behaviour between processes, taking into account both quantitative aspects and contextual information. This way, process distances by construction take the environment into account: two (non-equivalent) processes may still exhibit very similar behaviour in some contexts, e.g., when certain actions are never performed. We first show how CBMs capture many well-known notions of equivalence and metric, including Larsen’s environmental parametrized bisimulation. We then study compositional properties of CBMs with respect to some common process algebraic operators, namely prefixing, restriction, non-deterministic sum, parallel composition and replication
A Sound Up-to-, Bisimilarity for PCTL
We tackle the problem of establishing the soundness of approximate
bisimilarity with respect to PCTL and its relaxed semantics. To this purpose,
we consider a notion of bisimilarity similar to the one introduced by
Desharnais, Laviolette, and Tracol, which is parametric with respect to an
approximation error , and to the depth of the observation along
traces. Essentially, our soundness theorem establishes that, when a state
satisfies a given formula up-to error and steps , and is
bisimilar to up-to error and enough steps, we prove that
also satisfies the formula up-to a suitable error and steps . The
new error is computed from , and the formula, and
only depends linearly on . We provide a detailed overview of our soundness
proof
On Urgency in Asynchronous Timed Session Types
We study an urgent semantics of asynchronous timed session types, where input actions happen as soon as possible. We show that with this semantics we can recover to the timed setting an appealing property of untimed session types: namely, deadlock-freedom is preserved when passing from synchronous to asynchronous communication
A theory of transaction parallelism in blockchains
Decentralized blockchain platforms have enabled the secure exchange of
crypto-assets without the intermediation of trusted authorities. To this
purpose, these platforms rely on a peer-to-peer network of byzantine nodes,
which collaboratively maintain an append-only ledger of transactions, called
blockchain. Transactions represent the actions required by users, e.g. the
transfer of some units of crypto-currency to another user, or the execution of
a smart contract which distributes crypto-assets according to its internal
logic. Part of the nodes of the peer-to-peer network compete to append
transactions to the blockchain. To do so, they group the transactions sent by
users into blocks, and update their view of the blockchain state by executing
these transactions in the chosen order. Once a block of transactions is
appended to the blockchain, the other nodes validate it, re-executing the
transactions in the same order. The serial execution of transactions does not
take advantage of the multi-core architecture of modern processors, so
contributing to limit the throughput. In this paper we develop a theory of
transaction parallelism for blockchains, which is based on static analysis of
transactions and smart contracts. We illustrate how blockchain nodes can use
our theory to parallelize the execution of transactions. Initial experiments on
Ethereum show that our technique can improve the performance of nodes.Comment: arXiv admin note: text overlap with arXiv:1905.0436
Verifying liquidity of recursive Bitcoin contracts
Smart contracts - computer protocols that regulate the exchange of
crypto-assets in trustless environments - have become popular with the spread
of blockchain technologies. A landmark security property of smart contracts is
liquidity: in a non-liquid contract, it may happen that some assets remain
frozen, i.e. not redeemable by anyone. The relevance of this issue is witnessed
by recent liquidity attacks to Ethereum, which have frozen hundreds of USD
millions. We address the problem of verifying liquidity on BitML, a DSL for
smart contracts with a secure compiler to Bitcoin, featuring primitives for
currency transfers, contract renegotiation and consensual recursion. Our main
result is a verification technique for liquidity. We first transform the
infinite-state semantics of BitML into a finite-state one, which focusses on
the behaviour of a chosen set of contracts, abstracting from the moves of the
context. With respect to the chosen contracts, this abstraction is sound, i.e.
if the abstracted contract is liquid, then also the concrete one is such. We
then verify liquidity by model-checking the finite-state abstraction. We
implement a toolchain that automatically verifies liquidity of BitML contracts
and compiles them to Bitcoin, and we assess it through a benchmark of
representative contracts.Comment: arXiv admin note: text overlap with arXiv:2003.0029
Glueball production in radiative J/psi, Upsilon decays
Using a bound-state model of weakly bound gluons for glueballs made of two
gluons and a natural generalization of the perturbative QCD formalism for
exclusive hadronic processes, we present results for glueball production in
radiative J/psi, Upsilon decays into several possible glueball states,
including L \not= 0 ones. We perform a detailed phenomenological analysis,
presenting results for the more favored experimental candidates and for decay
angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure
Metabolic profile of patients with severe endometriosis: a prospective experimental study
Endometriosis is a common disease affecting women in reproductive age. There are several hypotheses on the pathogenesis of this disease. Often, its lesions and symptoms overlap with those of many other medical and surgical conditions, causing a delay in diagnosis. Metabolomics represents a useful diagnostic tool for the study of metabolic changes during a different physiological or pathological status. We used 1H-NMR to explore metabolic alteration in a cohort of patients with endometriosis in order to contribute to a better understanding of the pathophysiology of the disease and to suggest new useful biomarkers. Thirty-seven patients were recruited for the metabolomic analysis: 22 patients affected by symptomatic endometriosis and 15 not affected by it. Their serum samples were collected and analyzed with 1H-NMR. Multivariate statistical analysis was conducted, followed by univariate and pathway analyses. Partial Least Square Discriminant Analysis (PLS-DA) was performed to determine the presence of any differences between the non-endometriosis and endometriosis samples (R2X = 0.596, R2Y = 0.713, Q2 = 0.635, and p < 0.0001). β-hydroxybutyric acid and glutamine were significantly increased, whereas tryptophan was significantly decreased in the endometriosis patients. ROC curves were built to test the diagnostic power of the metabolites (β-hydroxybutyric acid: AUC = 0.85 CI = 0.71–0.99; glutamine: AUC = 0.83 CI = 0.68–0.98; tryptophan: AUC = 0.75 CI = 0.54–0.95; β-hydroxybutyric acid + glutamine + tryptophan AUC = 0.92 CI = 0.81–1). The metabolomic approach enabled the identification
of several metabolic alterations occurring in women with endometriosis. These findings may provide new bases for a better
understanding of the pathophysiological mechanisms of the disease and for the discovery of new biomarkers. Trial registration
number NCT0233781
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