## 7 Experimentation of ArTIC-MS: Federation with OCEAN
On the other hand, the experimentation, along with the preliminary evaluation conducted in [12], has also revealed some limitations, which are mainly due to the maturity level of the TOSCA-related technologies and the limited support of the TOSCA standard. It must be pointed out that TOSCA is not currently supported by most of the relevant players in the cloud marketplace (e.g., Amazon, Google, and Microsoft). Moreover, in a few years the underlying standard adopted for specifying TOSCA templates has evolved from XML (extensible markup language) to YAML and, besides that, the TOSCA conceptual model has also been slightly revised. While this fact demonstrates the vitality of the TOSCA developers community, the lack of a road map that clearly outlines how the standard will be evolved in the next future might constitute limitations in its widespread adoption. Regarding the supporting tool for converting TOSCA templates to templates based on different languages (and vice versa), the availability of the HEAT Translator is a relevant starting point that we exploited for pushing the reusability and the portability of M&S services. Nonetheless, several efforts have to be spent in this direction. Currently, the HEAT Translator only supports the translation from TOSCA to HOT, while the opposite translation has to be addressed by ad-hoc extensions. Moreover, regarding the usability of HEAT Translator, in case of translation errors, the tool lacks verbose messages, which might help users to investigate and identify the specific problem. ## 8 Conclusions

This work investigated architectural approaches to support the FAIR principles in the development of heterogeneous federations of MSAaS infrastructure. The development of distributed simulations built as orchestrations of M&S services is a complex task that becomes even more difficult when the service composition includes M&S services provided by the heterogeneous infrastructure. In order to easily address this objective, the identification of an appropriate architecture assumes paramount relevance. In this context, this work first proposes a reference architecture for identifying building blocks and relevant capabilities that a concrete MSAaS infrastructure architecture should provide to effectively deal with MSAaS federations. Moreover, this work investigated the role of TOSCA as a valuable standard to foster M&S service interoperability and portability in heterogeneous federations. In this respect, ArTIC-MS, a conceptual architecture based on the proposed RA, was introduced. In order to provide effective guidance for implementing concrete MSAaS infrastructure in a federated environment, ArTIC-MS exploits the TOSCA standard and includes the specification of actors and use cases to define the relevant operational view. This work also discussed experimentation focused on a maritime defense scenario built by orchestrating services in a heterogeneous MSAaS federated infrastructure. According to the experimentation results, the capabilities provided by ArTIC-MS support the findability, accessibility, interoperability, and reusability of M&S services in heterogeneous infrastructure. In this respect, TOSCA constitutes a promising standard for dealing with service portability and their interoperable orchestration in a federated MSAaS infrastructure. Relevant issues that require further investigations include the actual adoption of TOSCA in significant and large-sized implementations, in both industry and academia, as well as the availability of open-source and commercial tools for translating various languages for services deployment and orchestration in the cloud. Further work includes the development of a complete ArTIC-MS implementation based on a TOSCA-compliant cloud infrastructure and its evaluation in a heterogeneous federation. Moreover, additional effort is required to investigate methods, tools, and languages for _application orchestration_, in order to appropriately extend the RA _composition service_ and the ArTIC-MS _composer_ building blocks. Conceptualization, P.B.