6,469 research outputs found
Embedding object-oriented design in system engineering
The Unified Modeling Language (UML) is a collection of techniques intended to document design decisions about software. This contrasts with systems engineering approaches such as for exampleStatemate and the Yourdon Systems Method (YSM), in which the design of an entire system consisting of software and hardware can be documented. The difference between the system- and the software level is reflected in differences between execution semantics as well as in methodology. In this paper, I show how the UML can be used as a system-level design technique. I give a conceptual framework for engineering design that accommodates the system- as well as the software level and show how techniques from the UML and YSM can be classified within this framework, and how this allows a coherent use of these techniques in a system engineering approach. These ideas are illustrated by a case study in which software for a compact dynamic bus station is designed. Finally, I discuss the consequences of this approach for a semantics of UML constructs that would be appropriate for system-level design
Well structured program equivalence is highly undecidable
We show that strict deterministic propositional dynamic logic with
intersection is highly undecidable, solving a problem in the Stanford
Encyclopedia of Philosophy. In fact we show something quite a bit stronger. We
introduce the construction of program equivalence, which returns the value
precisely when two given programs are equivalent on halting
computations. We show that virtually any variant of propositional dynamic logic
has -hard validity problem if it can express even just the equivalence
of well-structured programs with the empty program \texttt{skip}. We also show,
in these cases, that the set of propositional statements valid over finite
models is not recursively enumerable, so there is not even an axiomatisation
for finitely valid propositions.Comment: 8 page
RAFCON: a Graphical Tool for Task Programming and Mission Control
There are many application fields for robotic systems including service
robotics, search and rescue missions, industry and space robotics. As the
scenarios in these areas grow more and more complex, there is a high demand for
powerful tools to efficiently program heterogeneous robotic systems. Therefore,
we created RAFCON, a graphical tool to develop robotic tasks and to be used for
mission control by remotely monitoring the execution of the tasks. To define
the tasks, we use state machines which support hierarchies and concurrency.
Together with a library concept, even complex scenarios can be handled
gracefully. RAFCON supports sophisticated debugging functionality and tightly
integrates error handling and recovery mechanisms. A GUI with a powerful state
machine editor makes intuitive, visual programming and fast prototyping
possible. We demonstrated the capabilities of our tool in the SpaceBotCamp
national robotic competition, in which our mobile robot solved all exploration
and assembly challenges fully autonomously. It is therefore also a promising
tool for various RoboCup leagues.Comment: 8 pages, 5 figure
Formalising behaviour trees with CSP
Behaviour Trees is a novel approach for requirements engineering. It advocates a graphical tree notation that is easy to use and to understand. Individual requirements axe modelled as single trees which later on are integrated into a model of the system as a whole. We develop a formal semantics for a subset of Behaviour Trees using CSP. This work, on one hand, provides tool support for Behaviour Trees. On the other hand, it builds a front-end to a subset of the CSP notation and gives CSP users a new modelling strategy which is well suited to the challenges of requirements engineering
Matching Subsequences in Trees
Given two rooted, labeled trees and the tree path subsequence problem
is to determine which paths in are subsequences of which paths in . Here
a path begins at the root and ends at a leaf. In this paper we propose this
problem as a useful query primitive for XML data, and provide new algorithms
improving the previously best known time and space bounds.Comment: Minor correction of typos, et
Biocharts: a visual formalism for complex biological systems
We address one of the central issues in devising languages, methods and tools for the modelling and analysis of complex biological systems, that of linking high-level (e.g. intercellular) information with lower-level (e.g. intracellular) information. Adequate ways of dealing with this issue are crucial for understanding biological networks and pathways, which typically contain huge amounts of data that continue to grow as our knowledge and understanding of a system increases. Trying to comprehend such data using the standard methods currently in use is often virtually impossible. We propose a two-tier compound visual language, which we call Biocharts, that is geared towards building fully executable models of biological systems. One of the main goals of our approach is to enable biologists to actively participate in the computational modelling effort, in a natural way. The high-level part of our language is a version of statecharts, which have been shown to be extremely successful in software and systems engineering. The statecharts can be combined with any appropriately well-defined language (preferably a diagrammatic one) for specifying the low-level dynamics of the pathways and networks. We illustrate the language and our general modelling approach using the well-studied process of bacterial chemotaxis
Molecular Model of Dynamic Social Network Based on E-mail communication
In this work we consider an application of physically inspired sociodynamical model to the modelling of the evolution of email-based social network. Contrary to the standard approach of sociodynamics, which assumes expressing of system dynamics with heuristically defined simple rules, we postulate the inference of these rules from the real data and their application within a dynamic molecular model. We present how to embed the n-dimensional social space in Euclidean one. Then, inspired by the Lennard-Jones potential, we define a data-driven social potential function and apply the resultant force to a real e-mail communication network in a course of a molecular simulation, with network nodes taking on the role of interacting particles. We discuss all steps of the modelling process, from data preparation, through embedding and the molecular simulation itself, to transformation from the embedding space back to a graph structure. The conclusions, drawn from examining the resultant networks in stable, minimum-energy states, emphasize the role of the embedding process projecting the nonāmetric social graph into the Euclidean space, the significance of the unavoidable loss of information connected with this procedure and the resultant preservation of global rather than local properties of the initial network. We also argue applicability of our method to some classes of problems, while also signalling the areas which require further research in order to expand this applicability domain
Synthesizing Finite-state Protocols from Scenarios and Requirements
Scenarios, or Message Sequence Charts, offer an intuitive way of describing
the desired behaviors of a distributed protocol. In this paper we propose a new
way of specifying finite-state protocols using scenarios: we show that it is
possible to automatically derive a distributed implementation from a set of
scenarios augmented with a set of safety and liveness requirements, provided
the given scenarios adequately \emph{cover} all the states of the desired
implementation. We first derive incomplete state machines from the given
scenarios, and then synthesis corresponds to completing the transition relation
of individual processes so that the global product meets the specified
requirements. This completion problem, in general, has the same complexity,
PSPACE, as the verification problem, but unlike the verification problem, is
NP-complete for a constant number of processes. We present two algorithms for
solving the completion problem, one based on a heuristic search in the space of
possible completions and one based on OBDD-based symbolic fixpoint computation.
We evaluate the proposed methodology for protocol specification and the
effectiveness of the synthesis algorithms using the classical alternating-bit
protocol.Comment: This is the working draft of a paper currently in submission.
(February 10, 2014
Non-Holonomic Control IV : Coherence Protection in a Rubidium isotope
In this paper, we present a realistic application of the coherence protection
method proposed in the previous article. A qubit of information encoded on the
two spin states of a Rubidium isotope is protected from the action of electric
and magnetic fields
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