8,258 research outputs found
Formal Verification of Real-Time Function Blocks Using PVS
A critical step towards certifying safety-critical systems is to check their
conformance to hard real-time requirements. A promising way to achieve this is
by building the systems from pre-verified components and verifying their
correctness in a compositional manner. We previously reported a formal approach
to verifying function blocks (FBs) using tabular expressions and the PVS proof
assistant. By applying our approach to the IEC 61131-3 standard of Programmable
Logic Controllers (PLCs), we constructed a repository of precise specification
and reusable (proven) theorems of feasibility and correctness for FBs. However,
we previously did not apply our approach to verify FBs against timing
requirements, since IEC 61131-3 does not define composite FBs built from
timers. In this paper, based on our experience in the nuclear domain, we
conduct two realistic case studies, consisting of the software requirements and
the proposed FB implementations for two subsystems of an industrial control
system. The implementations are built from IEC 61131-3 FBs, including the
on-delay timer. We find issues during the verification process and suggest
solutions.Comment: In Proceedings ESSS 2015, arXiv:1506.0325
Algebraic Bethe ansatz for the gl(12) generalized model II: the three gradings
The algebraic Bethe ansatz can be performed rather abstractly for whole
classes of models sharing the same -matrix, the only prerequisite being the
existence of an appropriate pseudo vacuum state. Here we perform the algebraic
Bethe ansatz for all models with , rational, gl(12)-invariant
-matrix and all three possibilities of choosing the grading. Our Bethe
ansatz solution applies, for instance, to the supersymmetric t-J model, the
supersymmetric model and a number of interesting impurity models. It may be
extended to obtain the quantum transfer matrix spectrum for this class of
models. The properties of a specific model enter the Bethe ansatz solution
(i.e. the expression for the transfer matrix eigenvalue and the Bethe ansatz
equations) through the three pseudo vacuum eigenvalues of the diagonal elements
of the monodromy matrix which in this context are called the parameters of the
model.Comment: paragraph added in section 3, reference added, version to appear in
J.Phys.
ILP Modulo Data
The vast quantity of data generated and captured every day has led to a
pressing need for tools and processes to organize, analyze and interrelate this
data. Automated reasoning and optimization tools with inherent support for data
could enable advancements in a variety of contexts, from data-backed decision
making to data-intensive scientific research. To this end, we introduce a
decidable logic aimed at database analysis. Our logic extends quantifier-free
Linear Integer Arithmetic with operators from Relational Algebra, like
selection and cross product. We provide a scalable decision procedure that is
based on the BC(T) architecture for ILP Modulo Theories. Our decision procedure
makes use of database techniques. We also experimentally evaluate our approach,
and discuss potential applications.Comment: FMCAD 2014 final version plus proof
Is a Dataframe Just a Table?
Querying data is core to databases and data science. However, the two communities have seemingly different concepts and use cases. As a result, both designers and users of the query languages disagree on whether the core abstractions - dataframes (data science) and tables (databases) - and the operations are the same. To investigate the difference from a PL-HCI perspective, we identify the basic affordances provided by tables and dataframes and how programming experiences over tables and dataframes differ. We show that the data structures nudge programmers to query and store their data in different ways. We hope the case study could clarify confusions, dispel misinformation, increase cross-pollination between the two communities, and identify open PL-HCI questions
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