Philippe Merle

Background: Topology and Orchestration Specification for Cloud Applications (TOSCA) is a specification language used for modelling topology and orchestration of cloud applications. This language particularly allows the description of workflows that can be used for specifying management tasks such as (un)deployment plans. Motivations: This textual language for describing TOSCA workflows does not provide any visual notation for graphically designing or observing the corresponding workflows. Moreover, this specification language is error‐prone and can be source of mistakes during the writing of the management plans. Methods: In this article, we propose a transformation from TOSCA to the graphical Business Process Model and Notation (BPMN), which allows the visualisation of TOSCA workflows. We also provide automated verification techniques for analysing TOSCA (un)deployment workflows in terms of functional and architectural properties as well as execution times. The transformation and verification steps are achieved in a fully automated way. Results: This approach computes BPMN models and verification results within a reasonable time on realistic applications.

Modern distributed applications increasingly rely on cloud-native platforms to abstract the complexity of deployment and scalability. As the de facto orchestration standard, Kubernetes enables this abstraction, but its declarative configuration model makes the architectural understanding difficult. Developers, operators, and architects struggle to form accurate mental models from raw manifests, Helm charts, or cluster state descriptions. We introduce KubeDiagrams, an open-source tool that transforms Kubernetes manifests into architecture diagrams. By grounding our design in a user-centered study of real-world visualization practices, we identify the specific challenges Kubernetes users face and map these to concrete design requirements. KubeDiagrams integrates seamlessly with standard Kubernetes artifacts, preserves semantic fidelity to core concepts, and supports extensibility and automation. We detail the tool's architecture, visual encoding strategies, and extensibility mechanisms. Three case studies illustrate how KubeDiagrams enhances system comprehension and supports architectural reasoning in distributed cloud-native systems. KubeDiagrams addresses concrete pain points in Kubernetes-based DevOps practices and is valued for its automation, clarity, and low-friction integration into real-world tooling environments.

With the advent of cloud computing, different cloud providers with heterogeneous cloud services (compute, storage, network, applications, etc.) and their related Application Programming Interfaces (APIs) have emerged. This heterogeneity complicates the implementation of an interoperable cloud system. Several standards have been proposed to address this challenge and provide a unified interface to cloud resources. The Open Cloud Computing Interface (OCCI) thereby focuses on the standardization of a common API for Infrastructure-as-a-Service (IaaS) providers while the Topology and Orchestration Specification for Cloud Applications (TOSCA) focuses on the standardization of a template language to enable the proper definition of the topology of cloud applications and their orchestrations on top of a cloud system. TOSCA thereby does not define how the application topologies are created on the cloud. Therefore, we analyse the conceptual similarities between the two approaches and we study how we can integrate them to obtain a complete standard-based approach to manage both cloud infrastructure and cloud application layers. We propose an automated extensive mapping between the concepts of the two standards and we provide TOSCA Studio, a model-driven tool chain for TOSCA that conforms to OCCI. TOSCA Studio allows to graphically design cloud applications as well as to deploy and manage them at runtime using a fully model-driven cloud orchestrator based on the two standards. Our contribution is validated by successfully designing and deploying three cloud applications: WordPress, Node Cellar and Multi-Tier.

Elasticity is considered as a fundamental feature of cloud computing where the system capacity can adjust to the current application workloads by provisioning or de-provisioning computing resources automatically and timely. Many studies have been already conducted to elasticity management systems, however, almost all lack to offer a complete modular solution. In this article, we propose MoDEMO, a new elasticity management system powering both vertical and horizontal elasticities, both VM and Container virtualization technologies, multiple cloud providers simultaneously, and various elasticity policies. MoDEMO is characterized by the following features: it represents (i) the first system that manages elasticity using Open Cloud Computing Interface (OCCI) model with respect to the OCCI standard specifications, (ii) the first unified system which combines the functionalities of the worldwide cloud providers: Amazon Web Services (AWS), Microsoft Azure and Google Cloud Platform (GCP), and (iii) allows a dynamic configuration at runtime during the execution of the application. MoDEMO permits to timely adapt resource capacity according to the workload intensity and increase application performance without introducing a significant overhead.

We demonstrate a lightweight toolchain for validating descriptors of network functions compliant with the latest ETSI NFV standards, visualizing these descriptors in the form of various diagrams (i.e. network-oriented, function-oriented, and UML2-based), analyzing these descriptors formally with the Alloy Analyzer, and deploying these virtualized network functions on OpenStack.