2,431,289 research outputs found
Data-Flow Based Model Analysis
The concept of (meta) modeling combines an intuitive way of formalizing the structure of an application domain with a high expressiveness that makes it suitable for a wide variety of use cases and has therefore become an integral part of many areas in computer science. While the definition of modeling languages through the use of meta models, e.g. in Unified Modeling Language (UML), is a well-understood process, their validation and the extraction of behavioral information is still a challenge. In this paper we present a novel approach for dynamic model analysis along with several fields of application. Examining the propagation of information along the edges and nodes of the model graph allows to extend and simplify the definition of semantic constraints in comparison to the capabilities offered by e.g. the Object Constraint Language. Performing a flow-based analysis also enables the simulation of dynamic behavior, thus providing an "abstract interpretation"-like analysis method for the modeling domain
Object-based Control/Data-flow Analysis
Not only does a clear distinction between control and data flow enhance the readability of models, but it also allows different tools to operate on the two distinct parts of the model. This paper shows how the modelling based on control/data-flow analysis can benefit from an object-based approach. We have developed a translation mechanism that is faithful and gives an extra dimension (hierarchy) to the existing paradigm of control and data flow interacting in a model. Our methodology provides a comprehensible separation of these two parts, which can be used to feed another analysis or synthesis tools, while still being able to reason about both parts through formal methods of verification
Static Safety for an Actor Dedicated Process Calculus by Abstract Interpretation
The actor model eases the definition of concurrent programs with non uniform
behaviors. Static analysis of such a model was previously done in a data-flow
oriented way, with type systems. This approach was based on constraint set
resolution and was not able to deal with precise properties for communications
of behaviors. We present here a new approach, control-flow oriented, based on
the abstract interpretation framework, able to deal with communication of
behaviors. Within our new analyses, we are able to verify most of the previous
properties we observed as well as new ones, principally based on occurrence
counting
Enabling Operator Reordering in Data Flow Programs Through Static Code Analysis
In many massively parallel data management platforms, programs are
represented as small imperative pieces of code connected in a data flow. This
popular abstraction makes it hard to apply algebraic reordering techniques
employed by relational DBMSs and other systems that use an algebraic
programming abstraction. We present a code analysis technique based on reverse
data and control flow analysis that discovers a set of properties from user
code, which can be used to emulate algebraic optimizations in this setting.Comment: 4 pages, accepted and presented at the First International Workshop
on Cross-model Language Design and Implementation (XLDI), affiliated with
ICFP 2012, Copenhage
A Methodology for Information Flow Experiments
Information flow analysis has largely ignored the setting where the analyst
has neither control over nor a complete model of the analyzed system. We
formalize such limited information flow analyses and study an instance of it:
detecting the usage of data by websites. We prove that these problems are ones
of causal inference. Leveraging this connection, we push beyond traditional
information flow analysis to provide a systematic methodology based on
experimental science and statistical analysis. Our methodology allows us to
systematize prior works in the area viewing them as instances of a general
approach. Our systematic study leads to practical advice for improving work on
detecting data usage, a previously unformalized area. We illustrate these
concepts with a series of experiments collecting data on the use of information
by websites, which we statistically analyze
Analytical considerations of flow boiling heat transfer in metal-foam filled tubes
Flow boiling in metal-foam filled tube was analytically investigated based on a modified microstructure model, an original boiling heat transfer model and fin analysis for metal foams. Microstructure model of metal foams was established, by which fiber diameter and surface area density were precisely predicted. The heat transfer model for flow boiling in metal foams was based on annular pattern, in which two phase fluid was composed by vapor region in the center of the tube and liquid region near the wall. However, it was assumed that nucleate boiling performed only in the liquid region. Fin analysis and heat transfer network for metal foams were integrated to obtain the convective heat transfer coefficient at interface. The analytical solution was verified by its good agreement with experimental data. The parametric study on heat transfer coefficient and boiling mechanism was also carried out
Two-phase flow dynamics in a micro hydrophilic channel: A theoretical and experimental study
In this paper, two-phase flow dynamics in a micro hydrophilic channel are experimentally and theoretically investigated. Flow patterns of annulus, wavy, and slug are observed in the range of operating condition. A set of empirical models based on the Lockhart-Martinelli parameter and a two-fluid model using several correlations of the relative permeability are adopted; and their predictions are compared with experimental data. It shows that for low liquid flow rates most model predictions show acceptable agreement with experimental data, while in the regime of high liquid flow rate only a few of them exhibit a good match. Correlation optimization is conducted for individual flow pattern. Through theoretical analysis of flows in a circular and 2-D channel, respectively, we obtain correlations close to the experimental observation. Real-time pressure measurement shows that different flow patterns yield different pressure evolutions. © 2013 Elsevier Ltd. All rights reserved
On The Modeling of OpenFlow-based SDNs: The Single Node Case
OpenFlow is one of the most commonly used protocols for communication between
the controller and the forwarding element in a software defined network (SDN).
A model based on M/M/1 queues is proposed in [1] to capture the communication
between the forwarding element and the controller. Albeit the model provides
useful insight, it is accurate only for the case when the probability of
expecting a new flow is small. Secondly, it is not straight forward to extend
the model in [1] to more than one forwarding element in the data plane. In this
work we propose a model which addresses both these challenges. The model is
based on Jackson assumption but with corrections tailored to the OpenFlow based
SDN network. Performance analysis using the proposed model indicates that the
model is accurate even for the case when the probability of new flow is quite
large. Further we show by a toy example that the model can be extended to more
than one node in the data plane.Comment: Published in Proceedings of CS & IT for NeCOM 201
- âŠ