# Enabling Role-Based Orchestration for Cloud Applications
## 4 Experimental Evaluation
### TOSCA Model Conversion Cost
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Our Approach** & **Tosker** & **TOSCAMP** & **Cloudify** & **KubeVela** \\ \hline Base & TOSCA 1.0 and & TOSCA 1.0 & TOSCA 1.0 and & TOSCA-based DSL & OAM 0.2.1 \\ Specification & OAM 0.2.1 & & CAMP 1.1 & & \\ \hline Application & TOSCA topology and & TOSCA topology & TOSCA topology & Models written in & Capabilities but \\ Model & capabilities & & Cloudify DSL & no topology \\ \hline Role-Awareness & Role-awareness & No role-awareness & No role-awareness & No role-awareness & Role-awareness \\ \hline Capability & Typed capability as & No capability & No capability & No capability & Typed capability as \\ Abstraction & model constructs & abstraction & abstraction & abstraction & model constructs \\ \hline Workflow & Imperative workflow & Declarative workflow & Imperative workflow & Built-in deployment- & No workflow \\ Definition & definition by TOSCA & definition by TOSCA & definition by TOSCA & specific workflows & definition \\ \hline Multi-Cloud & Multi-cloud support & No multi-cloud support & Multi-cloud support & Multi-cloud support & \\ Support & based on Kubernetes & support & based on lakes/PaaS standards & based on Kubernetes \\ \hline Cross-Cloud & Cross-cloud based on & No cross-cloud & Cross-cloud support & Cross-cloud based on & Cross-cloud based on \\ Support & Kubernetes Federation & support & based on standarized & Kubernetes Federation \\ \hline Containerization & Contained, CRI-O, & Only Docker & No communication & Contained, CRI-O, & Contained, CRI-O, \\ Support & and Docker & support & and Docker & and Docker \\ \hline \end{tabular}
\end{table} 
Table 3: Qualitative analysis of orchestration approaches. Considered as a mature and prominent topology specification, TOSCA is adopted by a number of cloud application orchestration solutions. TosKer [27] presents a Docker-based orchestration system that can manage the deployment and operation of TOSCA-based representations of applications in Kubernetes clusters. As a means to model cloud application topology, it introduces new TOSCA node types of Container and Software that represent a Docker container and a software component of the application, respectively. Interconnection and dependencies among them are defined by the TOSCA normative relationship types, including _AttachesTo, ConnectsTo, HostedOn_, and _DependsOn_. Given a TOSCA representation of a cloud application, the orchestration engine instantiates the application over a Kubernetes cluster. In this system, a container is the minimal entity that can be orchestrated. This rigid coupling of software components and their hosting containers is relaxed in their follow-up work [23], so that the components can be managed independently from their hosting containers. More specifically, the lifecycle of software components can be managed separately from that of their hosting containers. It is even made possible to have multiple components running in a single container for better inter-component communication latency and resource utilization. It is also shown that the orchestration process is further automated to allow for a partial topology description [28]. Given an incomplete specification of TOSCA applications, where only application-specific components are defined and other aspects are left unspecified, the proposed scheme can complete the TOSCA representation by automatically filling in unspecified parts. These research efforts focus on TOSCA orchestration systems tailored for container-based runtime environments. According to these proposals, TOSCA application components are mapped to Docker containers, and container orchestration technologies like Kubernetes and Docker Swarm are exploited as a base to build up a full-fledged orchestration system. Our proposal differs from these efforts in that TOSCA applications are mapped to underlying OAM entities. As a result, it can benefit from role-awareness and higher-level orchestration features enabled by OAM technology.