The orchestration layer is responsible for dispatching workflows’ tasks and jobs within the LEXIS infrastructural layer. To this end, the orchestration layer receive a description of the workflow (TOSCA file format) to run, and uses a set of internal policies to select the set of resources where to execute the tasks and jobs associated to the workflow. The orchestration layer is based on a Atos-provided solution named YSTIA, which has two main building blocks: an orchestration service (Yorc) and a front-end interface (Alien4Cloud). This latter offers also capability to model user applications in TOSCA. Managing HPC jobs is done through the integration of a plug-in module (HEAppE), which also provides, due to security reason, a solution for accessing HPC resources on IT4Innovations and LRZ infrastructures. The orchestration layer exposes the front-end interface as part of the LEXIS portal, as well as it relies on the other two key LEXIS layers, i.e., the LEXIS infrastructure layer and the The LEXIS Data Management layer. It also relies on the functionalities of the authentication and authorization infrastructure (AAI) to access resources and data for which the user has the rights.