4,267 research outputs found
Managing LTL properties in Event-B refinement
Refinement in Event-B supports the development of systems via proof based
step-wise refinement of events. This refinement approach ensures safety
properties are preserved, but additional reasoning is required in order to
establish liveness and fairness properties.
In this paper we present results which allow a closer integration of two
formal methods, Event-B and linear temporal logic. In particular we show how a
class of temporal logic properties can carry through a refinement chain of
machines. Refinement steps can include introduction of new events, event
renaming and event splitting. We also identify a general liveness property that
holds for the events of the initial system of a refinement chain. The approach
will aid developers in enabling them to verify linear temporal logic properties
at early stages of a development, knowing they will be preserved at later
stages. We illustrate the results via a simple case study
A Fixpoint Semantics of Event Systems with and without Fairness Assumptions
We present a fixpoint semantics of event systems. The semantics is presented
in a general framework without concerns of fairness. Soundness and completeness
of rules for deriving "leads-to" properties are proved in this general
framework. The general framework is instantiated to minimal progress and weak
fairness assumptions and similar results are obtained. We show the power of
these results by deriving sufficient conditions for "leads-to" under minimal
progress proving soundness of proof obligations without reasoning over
state-traces
Preserving Liveness Guarantees from Synchronous Communication to Asynchronous Unstructured Low-Level Languages
In the implementation of abstract synchronous communication in asynchronous unstructured low-level languages, e.g. using shared variables, the preservation of safety and especially liveness properties is a hitherto open problem due to inherently different abstraction levels. Our approach to overcome this problem is threefold: First, we present our notion of handshake refinement with which we formally prove the correctness of the implementation relation of a handshake protocol. Second, we verify the soundness of our handshake refinement, i.e., all safety and liveness properties are preserved to the lower level. Third, we apply our handshake refinement to show the correctness of all implementations that realize the abstract synchronous communication with the handshake protocol. To this end, we employ an exemplary language with asynchronous shared variable communication. Our approach is scalable and closes the verification gap between different abstraction levels of communication
Generalised Nonblocking
This paper studies the nonblocking check used in supervisory control of discrete event systems and its limitations. Different examples with different liveness requirements are discussed. It is shown that the standard nonblocking check can be used to specify most requirements of interest, but that it lacks expressive power in a few cases. A generalised nonblocking check is proposed to overcome the weakness, and its relationship to standard nonblocking is explored. Results suggest that generalised nonblocking, while having the same useful properties with respect to synthesis and compositional verification, can provide for more concise problem representations in some cases
A System for Deduction-based Formal Verification of Workflow-oriented Software Models
The work concerns formal verification of workflow-oriented software models
using deductive approach. The formal correctness of a model's behaviour is
considered. Manually building logical specifications, which are considered as a
set of temporal logic formulas, seems to be the significant obstacle for an
inexperienced user when applying the deductive approach. A system, and its
architecture, for the deduction-based verification of workflow-oriented models
is proposed. The process of inference is based on the semantic tableaux method
which has some advantages when compared to traditional deduction strategies.
The algorithm for an automatic generation of logical specifications is
proposed. The generation procedure is based on the predefined workflow patterns
for BPMN, which is a standard and dominant notation for the modeling of
business processes. The main idea for the approach is to consider patterns,
defined in terms of temporal logic,as a kind of (logical) primitives which
enable the transformation of models to temporal logic formulas constituting a
logical specification. Automation of the generation process is crucial for
bridging the gap between intuitiveness of the deductive reasoning and the
difficulty of its practical application in the case when logical specifications
are built manually. This approach has gone some way towards supporting,
hopefully enhancing our understanding of, the deduction-based formal
verification of workflow-oriented models.Comment: International Journal of Applied Mathematics and Computer Scienc
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