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SPIN-ning Software Architectures: A Method for Exploring Complex Systems
When designing complex software systems that provide multiple non-functional properties, it is usual to try to reuse (and finally compose) simpler existing designs, which deal with each of these properties in solitude. The paper describes a method for automatically and quickly identifying all the different ways one can compose such designs, with the aid of a model checke
Permission-Based Separation Logic for Multithreaded Java Programs
This paper presents a program logic for reasoning about multithreaded
Java-like programs with dynamic thread creation, thread joining and reentrant
object monitors. The logic is based on concurrent separation logic. It is the
first detailed adaptation of concurrent separation logic to a multithreaded
Java-like language. The program logic associates a unique static access
permission with each heap location, ensuring exclusive write accesses and
ruling out data races. Concurrent reads are supported through fractional
permissions. Permissions can be transferred between threads upon thread
starting, thread joining, initial monitor entrancies and final monitor exits.
In order to distinguish between initial monitor entrancies and monitor
reentrancies, auxiliary variables keep track of multisets of currently held
monitors. Data abstraction and behavioral subtyping are facilitated through
abstract predicates, which are also used to represent monitor invariants,
preconditions for thread starting and postconditions for thread joining.
Value-parametrized types allow to conveniently capture common strong global
invariants, like static object ownership relations. The program logic is
presented for a model language with Java-like classes and interfaces, the
soundness of the program logic is proven, and a number of illustrative examples
are presented
Collaborative Verification-Driven Engineering of Hybrid Systems
Hybrid systems with both discrete and continuous dynamics are an important
model for real-world cyber-physical systems. The key challenge is to ensure
their correct functioning w.r.t. safety requirements. Promising techniques to
ensure safety seem to be model-driven engineering to develop hybrid systems in
a well-defined and traceable manner, and formal verification to prove their
correctness. Their combination forms the vision of verification-driven
engineering. Often, hybrid systems are rather complex in that they require
expertise from many domains (e.g., robotics, control systems, computer science,
software engineering, and mechanical engineering). Moreover, despite the
remarkable progress in automating formal verification of hybrid systems, the
construction of proofs of complex systems often requires nontrivial human
guidance, since hybrid systems verification tools solve undecidable problems.
It is, thus, not uncommon for development and verification teams to consist of
many players with diverse expertise. This paper introduces a
verification-driven engineering toolset that extends our previous work on
hybrid and arithmetic verification with tools for (i) graphical (UML) and
textual modeling of hybrid systems, (ii) exchanging and comparing models and
proofs, and (iii) managing verification tasks. This toolset makes it easier to
tackle large-scale verification tasks
Subclassing errors, OOP, and practically checkable rules to prevent them
This paper considers an example of Object-Oriented Programming (OOP) leading
to subtle errors that break separation of interface and implementations. A
comprehensive principle that guards against such errors is undecidable. The
paper introduces a set of mechanically verifiable rules that prevent these
insidious problems. Although the rules seem restrictive, they are powerful and
expressive, as we show on several familiar examples. The rules contradict both
the spirit and the letter of the OOP. The present examples as well as available
theoretical and experimental results pose a question if OOP is conducive to
software development at all.Comment: 10 pages, 1 LaTeX file; accompanying C++ and Haskell code and
compilation instruction
Model Checker Execution Reports
Software model checking constitutes an undecidable problem and, as such, even
an ideal tool will in some cases fail to give a conclusive answer. In practice,
software model checkers fail often and usually do not provide any information
on what was effectively checked. The purpose of this work is to provide a
conceptual framing to extend software model checkers in a way that allows users
to access information about incomplete checks. We characterize the information
that model checkers themselves can provide, in terms of analyzed traces, i.e.
sequences of statements, and safe cones, and present the notion of execution
reports, which we also formalize. We instantiate these concepts for a family of
techniques based on Abstract Reachability Trees and implement the approach
using the software model checker CPAchecker. We evaluate our approach
empirically and provide examples to illustrate the execution reports produced
and the information that can be extracted
ProofPeer - A Cloud-based Interactive Theorem Proving System
ProofPeer strives to be a system for cloud-based interactive theorem proving.
After illustrating why such a system is needed, the paper presents some of the
design challenges that ProofPeer needs to meet to succeed. Contexts are
presented as a solution to the problem of sharing proof state among the users
of ProofPeer. Chronicles are introduced as a way to organize and version
contexts
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