Abdelouahed Gherbi

UML Profiles for Real-Time Systems and their Applications

Real-time systems (RTS) have strict timing constraints and limited resources. The satisfaction of RTS timing constraints is required for their correction. In order to reduce the cost due to late discovery of design flaws and/or violations of timing constraints of RTS as well as to speed up their development to cope with time-to-market requirements, it is important to validate, at early stages of the development process, the functional and nonfunctional properties of RTS. In addition, RTS complexity is continuously increasing which makes their design very challenging. UML, a graphical object-oriented modeling language, is suitable to deal with this complexity. UML also supports predictive, quantitative analysis through its real-time profiles. The objective of this paper is to review the most important UML profiles for real-time from the academia, the industry and/or standard organizations; and the research activity that revolves around these profiles.

Experimental Evaluation of OpenStack Compute Scheduler

In the Cloud Computing model, the computing resources are provided as a service in an on-demand and dynamic fashion. Efficient and flexible resource management is among the current research issues in the cloud computing context. We present in this paper a study focusing on the dynamic behavior of the scheduling functionality of an IaaS cloud built using OpenStack. Resorting to the principles of Design of Experiment (DOE), we use a screening design applied on a small-scale private Cloud in order to explore OpenStack Compute Scheduler. We present and discuss in this paper the main outcomes of an enhanced two-level fractional factorial balanced design and we outline our future work.

Leveraging Linux Containers to Achieve High Availability for Cloud Services

In this work, we present a novel approach that leverages Linux containers to achieve High Availability (HA) for cloud applications. A middleware that is comprised of a set of HA agents is defined to compensate the limitations of Linux containers in achieving HA. In our approach we start modeling at the application level, considering the dependencies among application components. We generate the proper scheduling scheme and then deploy the application across containers in the cloud. For each container that hosts critical component(s), we continuously monitor its status and checkpoint its full state, and then react to its failure by restarting locally or failing over to another host where we resume the computing from the most recent state. By using this strategy, all components hosted in a container are preserved without intrusively imposing modification on the application side. Finally, the feasibility of our approach is verified by building a proof-of-concept prototype and a case study of a video streaming application.

Openstack scheduler evaluation using design of experiment approach

Cloud computing is a computing model which is essentially characterized by an on-demand and dynamic provisioning of computing resources. In this model, a cloud is a large-scale distributed system which leverages internet and virtualization technologies to provide computing resources as a service. Efficient, flexible and dynamic resource management is among the most challenging research issues in this domain. In this context, we present a study focusing on the dynamic behavior of the scheduling functionality of an Infrastructure-as-a-Service (IaaS) cloud, namely OpenStack Scheduler. We aim, through this study at identifying the limitations of this scheduler and ultimately enabling its extension using enhanced metrics. Towards this end, we present a Design of Experiment (DOE) based approach for the evaluation of the OpenStack Scheduler behavior. In particular, we use the screening type of experiment to identify the factors with significant effects on the responses. In our context, these factors are the amount of memory and the number of CPU cores assigned to virtual machine (VM) and the amount of memory and the number of cores on physical nodes. More specifically, we present a two-level fractional factorial balanced with the resolution IV and four center points experimental design with no replication.

The Impact of the Model-Driven Approach to Software Engineering on Software Engineering Education

As businesses rely on software solutions to preserve their position in a highly competitive market, the need for reliable and robust software systems is vital. Lately, there has been a significant interest in building software using models as their main artifacts. Unlike traditional development techniques which tend to be code-centric, model driven approaches, such as the Model Driven Architecture (MDA) standard, stress the usage of models at all levels of the software development life-cycle. The MDA, which is supported by the Object Management Group (OMG), is based on a comprehensive set of standards including MOF, UML, and OCL, to mention a few. This paradigm shift in software engineering has impacted not only the way software is built but also the way software engineering is being taught - The standards introduce a significant body of knowledge that should be integrated in a software engineering curriculum. In this paper, we discuss the impact of the model-driven software engineering approach on software education. This discussion is based on an experience teaching a graduate course on model-driven software engineering at Concordia University.

E-Bunny: A Dynamic Compiler for Embedded Java Virtual Machines

A new acceleration technology for Java embedded virtual machines is presented in this paper. Based on the selective dynamic compilation technique, this technology addresses the J2ME/CLDC (Java 2 Micro Edition for Connected Limited Device Configuration) platform. The primary objective of our work is to come up with an ecient, lightweight and low-footprint accelerated embedded Java Virtual Machine. This is achieved by the means of integrating a selective dynamic compiler that we called E-Bunny into the J2ME/CLDC virtual machine KVM. This paper presents the motivations, the architecture, the design and the implementation issues of E-Bunny and how we addressed them. Experimental results on the performance of our modified KVM demonstrate that we accomplished a speedup of 400% with respect to the Sun’s latest version of KVM. This experimentation was carried on using standard J2ME benchmarks.

SDL 2013: Model-Driven Dependability Engineering

In this paper, we present how we created a Domain Specific Language (DSL) dedicated to IP Multimedia Subsystem (IMS) at Ericsson. First, we introduce IMS and how developers are burdened by its complexity when integrating it in their application. Then we describe the principles we followed to create our new IMS DSL from its core in the Scala language to its syntax. We then present how we integrated it in two existing projects and show how it can save time for developers and how readable the syntax of the IMS DSL is.

Exploring early availability requirements using use case maps

Non-functional aspects including time constraints, distribution and fault tolerance are critical in the design and implementation of distributed real-time systems. As a result, it is well recognized that non-functional requirements should be considered at the earliest stages of system development life cycle. The ability to model non-functional properties (such as timing constraints, availability, performance, and security) at the system requirements level not only facilitates the task of moving towards real-time design, but ultimately supports the early detection of errors through automated validation and verification. In this paper, we introduce a novel approach to describe availability features in Use Case Maps (UCM) specifications. The proposed approach relies on a mapping of availability architectural tactics to UCM components. We illustrate the application of our approach using the In Service Software Upgrade (ISSU) feature on IP routers.

From UML/SPT models to schedulability analysis: a metamodel-based transformation

UML through its profiling mechanism is well adapted for the modeling of real-time software requirements and designs. It is becoming the de facto standard. On the other hand, several real-time schedulability analysis techniques have been proposed in the literature. One of the current research challenges is in bridging the gap between the UML/SPT models and the well-established real-time schedulability analysis techniques. In this paper, we propose an MDA-compliant approach addressing this issue. We develop an UML metamodel for a well-established schedulability analysis technique. We propose a rule-based transformation between the UML/SPT schedulability analysis sub-profile metamodel and this metamodel. We illustrate our approach with an example

SMT-Based Cost Optimization Approach for the Integration of Avionic Functions in IMA and TTEthernet Architectures

The design of avionic systems is a complex engineering activity. The iterative integration approach helps in controlling the complexity of such activity. On the other hand, using such approach to design evolving systems requires the reconfiguration of scheduling parameters of already integrated parts. This reconfiguration results in a recertification process having a cost that depends on the criticality level of the affected application. We propose a new approach which helps the system designer at each integration step in establishing the new scheduling parameters that minimize such cost. In this work, we focus on the Integrated Modular Avionic (IMA) architecture connected through a Time-Triggered Ethernet (TTEthernet) network. We present a formal model for such systems and we use this model to define a set of constraints that ensure the real-time requirements. These constraints are expressed using an SMTbased language and we used the SMT-solver YICES to find automatically a feasible scheduling parameters that minimize the cost of integration. We show our framework at work by analyzing the iterative integration of some functionalities of the Flight Management System.