No abstract

No abstract

Application models are commonly used in the development of information systems. Recent trends have introduced techniques by which models can be directly transformed into execution code and thus become a single source for application design. Inherently, it has been challenging for software developers to become proficient in designing entire systems due to the complex chain of model transformations and the further refinements required to the code generated from the models. We propose an architectural framework for building the distributed information system applications in which the application models are directly interpreted during execution. This approach shortens the evaluation cycles and provides faster feedback to developers. Our framework is based on a holistic application model represented as a graph structure complemented with a procedural action scripting language that can express more complex software behavior. We present the implementation details of this framework architecture in a mobile cloud environment and evaluate its benefits in eleven projects for different customers in the retail, supply-chain management and merchandising domain involving 300 active application users. Our approach allowed engaging end-users in the software development process in the phase of specifying executable application models. It succeeded in shortening the requirements engineering process and automating the configuration and deployment process. Moreover, it benefited from the automatic synchronization of application updates for all active versions at the customer sites.

No abstract

With the emerging IoT and Cloud-based networked systems that rely heavily on virtualization technologies, elasticity becomes a dominant system engineering attribute for providing QoS-aware services to their users. Although the concept of elasticity can introduce significant QoS and cost benefits, its implementation in real systems is full of challenges. Indeed, nowadays systems are mainly distributed, built upon several layers of abstraction, and with centralized control mechanisms. In such a complex environment, controlling elasticity in a centralized manner might strongly penalize scalability. To overcome this issue, we can conveniently split the system in autonomous subsystems that implement elasticity mechanisms and run control policies in a decentralized manner. To efficiently and effectively cooperate with each other, the subsystems need to communicate among themselves to determine elasticity decisions that collectively improve the overall system performance. This new architecture calls for the development of new mechanisms and efficient policies. In this chapter, we focus on elasticity in IoT and Cloud-based systems, which can be geo-distributed also at the edge of the networks, and discuss its engineering perspectives along with various coordination mechanisms. We focus on the design choices that may affect the elasticity properties and provide an overview of some decentralized design patterns related to the coordination of elasticity decisions.