******************
Workflow Structure
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The backend applications for the |app| follow a standard workflow:

I. **Read the configuration file.** At the start of the workflow, the workflow settings specified in the configuration file are parsed (:ref:`Inputs <lblUserDefInputs>`). *Note that if a particular component application is excluded from the configuration file, then it is automatically skipped in the workflow.*

II. **Pre-process building and event data.** The workflow completes a one-time step of setting up BIM files (:ref:`Building <lblBuildingApp>` Application) for each building asset and assigning events to each building site (:ref:`RegionalMapping <lblRegionalMapApp>` Application).

III. **Set up and run simulations for each building asset.** From here, the workflow begins its iterative processes of running simulations for each building asset. The workflow runs two passes for each building asset: the supporting simulation files (from the :ref:`Event <lblEventApp>`, :ref:`Modeling <lblModelingApp>`, :ref:`EDP <lblEDPApp>`, and :ref:`Simulation <lblSimulationApp>` Applications) are set up in the first pass, and the workflow commands are executed in the second pass. At the end of the iteration, simulation results are used to perform damage/loss assessment (:ref:`DL <lblDLApp>` Application). When run remotely on DesignSafe, this iterative process is parallelized across computing resources.

IV. **Aggregate outputs for all building assets.** After iterating through simulations, the workflow aggregates the content of individual EDP.csv, DM.csv, and DV.csv results for every building asset into single output summary files (:ref:`Outputs <lblOutputs>`).



The structure of a general workflow is depicted in :numref:`figBackendApps` with the following keys:

- User-provided input files are shown in orange.
- Component applications are shown in blue. File dependencies for each component application are shown with arrows.
- Intermediate files produced by the workflow to propagate data are shown in grey.
- Output files provided to the user are shown in green.
- Within the parallelized workflow for running each building asset simulation, two passes through the component applications are illustrated: the first pass in setting up the intermediate files (in red), then the second pass of executing the simulation and producing output results (in green).

.. figure:: figures/backendapps.png
   :name: figBackendApps
   :align: center
   :figclass: align-center

   Diagram of backend applications workflow.



To view the commands associated with each step of the workflow, refer to :ref:`Reading the Log <lblreadingLog>`.