On the use of software models during software execution

Increasingly software systems are required to survive variations in their execution environment without or with only little human intervention. Such systems are called "eternal software systems". In contrast to the traditional view of development and execution as separate cycles, these modern software systems should not present such a separation. Research in MDE has been primarily concerned with the use of models during the first cycle or development (i.e. during the design, implementation, and deployment) and has shown excellent results. In this paper the author argues that an eternal software system must have a first-class representation of itself available to enable change. These runtime representations (or runtime models) will depend on the kind of dynamic changes that we want to make available during execution or on the kind of analysis we want the system to support. Hence, different models can be conceived. Self-representation inevitably implies the use of reflection. In this paper the author briefly summarizes research that supports the use of runtime models, and points out different issues and research questions

A Methodology for Eliciting and Ranking Control Points for Adaptive Systems

Designing an adaptive system to meet its quality constraints in the face of environmental uncertainties, such as variable demands, can be a challenging task. In cloud environment, a designer has to also consider and evaluate different control points, i.e., those variables that affect the quality of the software system. This thesis presents a method for eliciting, evaluating and ranking control points for web applications deployed in cloud environments. The proposed method consists of several phases that take a high-level stakeholders' adaptation goal and transform it into lower level MAPE-K loop control points. The MAPE-K loop is then activated at runtime using an adaptation algorithm. We conducted several experiments to evaluate the different phases of the methodology and we report the results and the lesson learnt

A survey on engineering approaches for self-adaptive systems (extended version)

The complexity of information systems is increasing in recent years, leading to increased effort for maintenance and configuration. Self-adaptive systems (SASs) address this issue. Due to new computing trends, such as pervasive computing, miniaturization of IT leads to mobile devices with the emerging need for context adaptation. Therefore, it is beneficial that devices are able to adapt context. Hence, we propose to extend the definition of SASs and include context adaptation. This paper presents a taxonomy of self-adaptation and a survey on engineering SASs. Based on the taxonomy and the survey, we motivate a new perspective on SAS including context adaptation

Reusable Event Types for Models at Runtime to Support the Examination of Runtime Phenomena

Abstract-Today's software is getting more and more complex and harder to understand. Models help to organize knowledge and emphasize the structure of a software at a higher abstraction level. While the usage of model-driven techniques is widely adopted during software construction, it is still an open research topic if models can also be used to make runtime phenomena more comprehensible as well. It is not obvious which models are suitable for manual analysis and which model elements can be related to what type of runtime events. This paper proposes a collection of runtime event types that can be reused for various systems and meta-models. Based on these event types, information can be derived which help human observers to assess the current system state. Our approach is applied in a case study and evaluated regarding generalisability and completeness by relating it to two different meta-models

Constructing runtime models with bigraphs to address ubiquitous computing service composition volatility

In this thesis, we explore the appropriateness of the language abstractions provided by Bigraphs to construct a model at runtime to tackle the problem of volatility in a service composition running on a mobile device. Our contributions to knowledge are as follows: 1) We have shown that Bigraphs (Milner, 2009) are suitable for expressing models at runtime. 2) We have offered Bigraph language abstractions as an appropriate solution to some of the research problems posed by the models at runtime community (Aßmann et al., 2012). 3) We have discussed the general lessons learnt from using Bigraphs for a practical application such as a model at runtime. 4) We have discussed the general lessons learnt from our experiences of designing models at runtime. 5) We have implemented the model at runtime using the BPL Tool (ITU, 2011) and have experimentally studied the response times of our Bigraphical model. We have suggested appropriate enhancements for the tool based on our experiences. We present techniques to parameterize the reaction rules so that the matching algorithm of the BPL Tool returns a single match giving us the ability to dynamically program the model at runtime. We also show how to query the Bigraph structure

A Middleware to Support Services Delivery in a Domain-Specific Virtual Machine

The increasing use of model-driven software development has renewed emphasis on using domain-specific models during application development. More specifically, there has been emphasis on using domain-specific modeling languages (DSMLs) to capture user-specified requirements when creating applications. The current approach to realizing these applications is to translate DSML models into source code using several model-to-model and model-to-code transformations. This approach is still dependent on the underlying source code representation and only raises the level of abstraction during development. Experience has shown that developers will many times be required to manually modify the generated source code, which can be error-prone and time consuming. An alternative to the aforementioned approach involves using an interpreted domain-specific modeling language (i-DSML) whose models can be directly executed using a Domain Specific Virtual Machine (DSVM). Direct execution of i-DSML models require a semantically rich platform that reduces the gap between the application models and the underlying services required to realize the application. One layer in this platform is the domain-specific middleware that is responsible for the management and delivery of services in the specific domain. In this dissertation, we investigated the problem of designing the domain-specific middleware of the DSVM to facilitate the bifurcation of the semantics of the domain and the model of execution (MoE) while supporting runtime adaptation and validation. We approached our investigation by seeking solutions to the following sub-problems: (1) How can the domain-specific knowledge (DSK) semantics be separated from the MoE for a given domain? (2) How do we define a generic model of execution (GMoE) of the middleware so that it is adaptable and realizes DSK operations to support delivery of services? (3) How do we validate the realization of DSK operations at runtime? Our research into the domain-specific middleware was done using an i-DSML for the user-centric communication domain, Communication Modeling Language (CML), and for microgrid energy management domain, Microgrid Modeling Language (MGridML). We have successfully developed a methodology to separate the DSK and GMoE of the middleware of a DSVM that supports specialization for a given domain, and is able to perform adaptation and validation at runtime

Adaptations dynamiques au contexte en informatique ambiante : propriétés logiques et temporelles

In ubiquitous computing, applications are built as a collaboration of computerized and communicating objects called devices. Because these devices can be mobile or subject to failures, this infrastructure evolves dynamically and unpredictably. Thus, to fit seamlessly into their environment and to provide the functionalities expected by users which are often more sustainable than the environment, applications must dynamically adapt to these changes. Each of these variable phenomena pursues its own dynamic. The challenge offered to adaptation mechanisms is to be able to consider them, with suitable dynamics.For this purpose, we propose an architectural model and an adaptation mechanism. The architectural model is based on four levels organized hierarchically according to their complexity and to the dynamics they can offer. We combine to this architectural model an adaptation mechanism. Based on the separation of concerns principle, our mechanism allows us to consider the variability of the system. Due to the unpredictability of the environment, the sets of adaptations that will be deployed by the upper levels of the architecture may not have been anticipated at design time. Also, thanks to some logical and temporal properties, these adaptations can be composed in non-anticipated way and with appropriate response time. The proposed mechanism, called cascaded aspects, is implemented using Aspects of Assembly and the WComp execution platform.En informatique ambiante, les applications sont construites en faisant interagir entre eux des objets informatisés et communicants appelés dispositifs. Parce que ces dispositifs peuvent être mobiles ou subir des pannes, cette infrastructure évolue dynamiquement et de manière imprévisible. Aussi, pour s’insérer de manière transparente dans leur environnement et fournir les fonctionnalités attendues par les utilisateurs, bien souvent plus pérennes que l’environnement sur lequel elles reposent, les applications doivent s’adapter dynamiquement à ces évolutions. Ces phénomènes variables poursuivant leur propre dynamique, le défi proposé aux mécanismes d’adaptation est d’être capable de les prendre encompte, avec une dynamique adaptée à chacun d’entre eux.Dans cette optique, nous proposons un modèle architectural ainsi qu’un mécanisme d’adaptation. Le modèle architectural repose sur quatre niveaux organisés hiérarchiquement en fonction de leur complexité et de la dynamique qu’ils peuvent offrir. Nous lui associons un mécanisme d’adaptation qui, à partir du principe de séparation des préoccupations permet d’exprimer la variabilité du système. En raison de l’imprévisibilité de l’environnement, les ensembles d’adaptations qui seront déployées par les niveaux supérieurs de l’architecture ne peuvent pas nécessairement être anticipés à la conception. Aussi, grâce à un ensemble de propriétés logiques et temporelles, ces adaptations peuvent être composées de manière non-anticipée dans des temps de réponse adaptés. Le mécanisme d’adaptation proposé, appelé cascade d’aspects, est expérimenté en se basant sur les Aspects d’Assemblages et la plateforme d’exécution WComp

Descriptive business process models at run-time

Today's competitive markets require organisations to react proactively to changes in their environment if financial and legal consequences are to be avoided. Since business processes are elementary parts of modern organisations they are also required to efficiently adapt to these changes in quick and flexible ways. This requirement demands a more dynamic handling of business processes, i.e. treating business processes as run-time artefacts rather than design-time artefacts. One general approach to address this problem is provided by the community of [email protected], which promotes methodologies concerned with self-adaptive systems where models reflect the system's current state at any point in time and allow immediate reasoning and adaptation mechanisms. However, in contrast to common self-adaptive systems the domain of business processes features two additional challenges: (i) a bigger than usual abstraction gap between the business process models and the actual run-time information of the enterprise system and (ii) the possibility of run-time deviations from the planned models. Developing an understanding of such processes is a crucial necessity in order to optimise business processes and dynamically adapt to changing demands. This thesis explores the potential of adopting and enhancing principles and mechanisms from the [email protected] domain to the business process domain for the purpose of run-time reasoning, i.e. investigating the potential role of Descriptive Business Process Models at Run-time (DBPMRTs) in the business process management domain. The DBPMRT is a model describing the enterprise system at run-time and thus enabling higher-level reasoning on the as-is state. Along with the specification of the DBPMRT, algorithms and an overall framework are proposed to establish and maintain a causal link from the enterprise system to the DBPMRT at run-time. Furthermore, it is shown that proactive higher-level reasoning on a DBPMRT in the form of performance prediction allows for more accurate results. By taking these steps the thesis addresses general challenges of business process management, e.g. dealing with frequently changing processes and shortening the business process life cycle. At the same time this thesis contributes to research in [email protected] by providing a complex real-world use case as well as a reference approach for dealing with volatile [email protected] of a higher abstraction level