40,370 research outputs found
Translating and Evolving: Towards a Model of Language Change in DisCoCat
The categorical compositional distributional (DisCoCat) model of meaning
developed by Coecke et al. (2010) has been successful in modeling various
aspects of meaning. However, it fails to model the fact that language can
change. We give an approach to DisCoCat that allows us to represent language
models and translations between them, enabling us to describe translations from
one language to another, or changes within the same language. We unify the
product space representation given in (Coecke et al., 2010) and the functorial
description in (Kartsaklis et al., 2013), in a way that allows us to view a
language as a catalogue of meanings. We formalize the notion of a lexicon in
DisCoCat, and define a dictionary of meanings between two lexicons. All this is
done within the framework of monoidal categories. We give examples of how to
apply our methods, and give a concrete suggestion for compositional translation
in corpora.Comment: In Proceedings CAPNS 2018, arXiv:1811.0270
Verificare: a platform for composable verification with application to SDN-Enabled systems
Software-Defined Networking (SDN) has become increasing prevalent
in both the academic and industrial communities. A new class of system built on
SDNs, which we refer to as SDN-Enabled, provide programmatic interfaces between
the SDN controller and the larger distributed system. Existing tools for SDN
verification and analysis are insufficiently expressive to capture
this composition of a network and a larger distributed system. Generic
verification systems are an infeasible solution, due to their monolithic
approach to modeling and rapid state-space explosion.
In this thesis we present a new compositional approach to system modeling and
verification that is particularly appropriate for SDN-Enabled systems.
Compositional models may have sub-components (such as switches and
end-hosts) modified, added, or removed with only minimal, isolated changes.
Furthermore, invariants may be defined over the composed system that restrict
its behavior, allowing assumptions to be added or removed and for components to
be abstracted away into the service guarantee that they provide (such as
guaranteed packet arrival). Finally, compositional modeling can minimize the
size of the state space to be verified by taking advantage of known model
structure.
We also present the Verificare platform, a tool chain for building
compositional models in our modeling language and automatically compiling them
to multiple off-the-shelf verification tools. The compiler outputs a minimal,
calculus-oblivious formalism, which is accessed by plugins via a translation
API. This enables a wide variety of requirements to be
verified. As new tools become available, the translator can easily be extended
with plugins to support them
Text encoders are performance bottlenecks in contrastive vision-language models
Performant vision-language (VL) models like CLIP represent captions using a
single vector. How much information about language is lost in this bottleneck?
We first curate CompPrompts, a set of increasingly compositional image captions
that VL models should be able to capture (e.g., single object, to
object+property, to multiple interacting objects). Then, we train text-only
recovery probes that aim to reconstruct captions from single-vector text
representations produced by several VL models. This approach doesn't require
images, allowing us to test on a broader range of scenes compared to prior
work. We find that: 1) CLIP's text encoder falls short on object relationships,
attribute-object association, counting, and negations; 2) some text encoders
work significantly better than others; and 3) text-only recovery performance
predicts multi-modal matching performance on ControlledImCaps: a new evaluation
benchmark we collect+release consisting of fine-grained compositional
images+captions. Specifically -- our results suggest text-only recoverability
is a necessary (but not sufficient) condition for modeling compositional
factors in contrastive vision+language models. We release data+code
Towards a Formal Framework for Mobile, Service-Oriented Sensor-Actuator Networks
Service-oriented sensor-actuator networks (SOSANETs) are deployed in
health-critical applications like patient monitoring and have to fulfill strong
safety requirements. However, a framework for the rigorous formal modeling and
analysis of SOSANETs does not exist. In particular, there is currently no
support for the verification of correct network behavior after node failure or
loss/addition of communication links. To overcome this problem, we propose a
formal framework for SOSANETs. The main idea is to base our framework on the
\pi-calculus, a formally defined, compositional and well-established formalism.
We choose KLAIM, an existing formal language based on the \pi-calculus as the
foundation for our framework. With that, we are able to formally model SOSANETs
with possible topology changes and network failures. This provides the basis
for our future work on prediction, analysis and verification of the network
behavior of these systems. Furthermore, we illustrate the real-life
applicability of this approach by modeling and extending a use case scenario
from the medical domain.Comment: In Proceedings FESCA 2013, arXiv:1302.478
Event-based Compositional Reasoning of Information-Flow Security for Concurrent Systems
High assurance of information-flow security (IFS) for concurrent systems is
challenging. A promising way for formal verification of concurrent systems is
the rely-guarantee method. However, existing compositional reasoning approaches
for IFS concentrate on language-based IFS. It is often not applicable for
system-level security, such as multicore operating system kernels, in which
secrecy of actions should also be considered. On the other hand, existing
studies on the rely-guarantee method are basically built on concurrent
programming languages, by which semantics of concurrent systems cannot be
completely captured in a straightforward way. In order to formally verify
state-action based IFS for concurrent systems, we propose a
rely-guarantee-based compositional reasoning approach for IFS in this paper. We
first design a language by incorporating ``Event'' into concurrent languages
and give the IFS semantics of the language. As a primitive element, events
offer an extremely neat framework for modeling system and are not necessarily
atomic in our language. For compositional reasoning of IFS, we use
rely-guarantee specification to define new forms of unwinding conditions (UCs)
on events, i.e., event UCs. By a rely-guarantee proof system of the language
and the soundness of event UCs, we have that event UCs imply IFS of concurrent
systems. In such a way, we relax the atomicity constraint of actions in
traditional UCs and provide a compositional reasoning way for IFS in which
security proof of systems can be discharged by independent security proof on
individual events. Finally, we mechanize the approach in Isabelle/HOL and
develop a formal specification and its IFS proof for multicore separation
kernels as a study case according to an industrial standard -- ARINC 653
Extending Hybrid CSP with Probability and Stochasticity
Probabilistic and stochastic behavior are omnipresent in computer controlled
systems, in particular, so-called safety-critical hybrid systems, because of
fundamental properties of nature, uncertain environments, or simplifications to
overcome complexity. Tightly intertwining discrete, continuous and stochastic
dynamics complicates modelling, analysis and verification of stochastic hybrid
systems (SHSs). In the literature, this issue has been extensively
investigated, but unfortunately it still remains challenging as no promising
general solutions are available yet. In this paper, we give our effort by
proposing a general compositional approach for modelling and verification of
SHSs. First, we extend Hybrid CSP (HCSP), a very expressive and process
algebra-like formal modeling language for hybrid systems, by introducing
probability and stochasticity to model SHSs, which is called stochastic HCSP
(SHCSP). To this end, ordinary differential equations (ODEs) are generalized by
stochastic differential equations (SDEs) and non-deterministic choice is
replaced by probabilistic choice. Then, we extend Hybrid Hoare Logic (HHL) to
specify and reason about SHCSP processes. We demonstrate our approach by an
example from real-world.Comment: The conference version of this paper is accepted by SETTA 201
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