723 research outputs found
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
A Denotational Semantics for Communicating Unstructured Code
An important property of programming language semantics is that they should
be compositional. However, unstructured low-level code contains goto-like
commands making it hard to define a semantics that is compositional. In this
paper, we follow the ideas of Saabas and Uustalu to structure low-level code.
This gives us the possibility to define a compositional denotational semantics
based on least fixed points to allow for the use of inductive verification
methods. We capture the semantics of communication using finite traces similar
to the denotations of CSP. In addition, we examine properties of this semantics
and give an example that demonstrates reasoning about communication and jumps.
With this semantics, we lay the foundations for a proof calculus that captures
both, the semantics of unstructured low-level code and communication.Comment: In Proceedings FESCA 2015, arXiv:1503.0437
Fault-Tolerance by Graceful Degradation for Car Platoons
The key advantage of autonomous car platoons are their short inter-vehicle distances that increase traffic flow and reduce fuel consumption. However, this is challenging for operational and functional safety. If a failure occurs, the affected vehicles cannot suddenly stop driving but instead should continue their operation with reduced performance until a safe state can be reached or, in the case of temporal failures, full functionality can be guaranteed again. To achieve this degradation, platoon members have to be able to compensate sensor and communication failures and have to adjust their inter-vehicle distances to ensure safety. In this work, we describe a systematic design of degradation cascades for sensor and communication failures in autonomous car platoons using the example of an autonomous model car. We describe our systematic design method, the resulting degradation modes, and formulate contracts for each degradation level. We model and test our resulting degradation controller in Simulink/Stateflow
An introduction to (Co)algebras and (Co)induction and their application to the semantics of programming languages
This report summarizes operational approaches to the formal
semantics of programming languages and shows that they can be
interpreted inductively by least fixed points as well as
coinductively by greatest fixed points. While the inductive
interpretation gives semantics to all terminating programs,
the coinductive one defines moreover also a semantics for all
non-terminating programs. This is especially important in
areas where programs do not terminate in general, e.g. data
bases, operating systems, or control software in embedded
systems. The semantic foundations described in this report can
be used to verify that transformations (e.g. in compilers) of
such software systems are correct.
In the course of this report, coalgebras and coinduction are
introduced, starting with a gentle intuitive motivation and
ending with a detailed mathematical description within the
notions of category theory
Out of the Shadows: What Legal Research Instruction Reveals about Incorporating Skills throughout the Curriculum
The article first examines the politics of curricular reform. Before a law school will be able to increase or improve any skills instruction, the targeted skill must be important to enough to affect the curriculum. For example, sometimes law schools send inconsistent messages about the importance of legal research instruction. While external voices such as ABA accreditation standards and surveys of the practicing bar have long-recognized importance of the skills of legal research, evidence of the importance of the skill in the law school curriculum is mixed. If asked, most faculty members will agree that a given skill, such as legal research, is important. However, for that skill to be integrated into the curriculum in a way that will substantially affect graduate competencies, the skill must be important enough in the hierarchy of the faculty and curriculum to justify the costs of curricular change
Three Views of the Academy: Legal Education and the Legal Profession in Transition
Reviewing James E. Milterno, The American Legal Profession in Crisis: Resistance and Responses to Change (Oxford University Press 2013); Deborah L. Rhode, Lawyers as Leaders (Oxford University Press 2013), and Robin L. West, Teaching Law: Justice, Politics, and the Demands of Professionalism (Cambridge University Press 2013)
- …