Software architecture

A special agent, called a MA , is used to manage workflows in the DIET architecture. It receives requests from clients containing the description of a workflow in a specific language (the MA XML workflow language for DAGs). The role of the MA is to determine how to schedule the tasks contained in the workflow in order to follow the precedence constraints between tasks, and how to map the tasks to appropriate resources in the DIET hierarchy.

The execution of individual tasks is actually delegated by the MA to the client that submitted the workflow. After submitting the workflow, the client is put in a waiting mode and it will receive individual requests from the MA to execute each task of the workflow. Therefore all data transfers are done only from the client to the SeD s and do not transit through the MA.

When all tasks are completed, the MA sends a release signal to the client which then retrieves the results if the execution was successful.

To use the MA, the client configuration file must include the parameter MADAGNAME with the appropriate name.

When the client uses a functional workflow (in Gwendia language) the DIET client library provides the logic for instanciating the workflow, generating the DAGs and sending them to the MA. Note that when several DAGs are generated, they are usually not independent as some data generated by one DAG may be used by another one.