JSON Structure

This document describes the complete JSON schema used by Hermes workflows.

Workflow JSON

The top-level structure of a Hermes workflow:

{
    "workflow": {
        "root": "FinalNodeName",
        "nodeList": ["Node1", "Node2", "Node3"],
        "solver": "simpleFoam",
        "Templates": {},
        "nodes": {
            "Node1": { ... },
            "Node2": { ... },
            "Node3": { ... }
        }
    }
}

Top-Level Fields

Field	Type	Required	Description
workflow	object	Yes	Container for the workflow definition
workflow.root	string/null	No	Name of the root (final) node. If null, auto-detected
workflow.nodeList	array	Yes	Ordered list of node names
workflow.nodes	object	Yes	Node definitions keyed by name
workflow.solver	string	No	Solver name (for OpenFOAM workflows)
workflow.Templates	object	No	Shared template definitions

Node JSON

Each node in the nodes object has this structure:

{
    "NodeName": {
        "type": "category.NodeType",
        "Execution": {
            "input_parameters": {
                "param1": "value1",
                "param2": "value2"
            }
        },
        "GUI": {
            "Schema": { ... },
            "uiSchema": { ... },
            "formData": { ... }
        },
        "requires": ["OtherNode"]
    }
}

Node Fields

Field	Type	Required	Description
type	string	Yes	Node type identifier
Execution	object	Yes	Execution configuration
Execution.input_parameters	object	Yes	Parameters for the node
GUI	object	No	FreeCAD GUI configuration
requires	array	No	Explicit dependencies
Template	string	No	Template reference (alternative to full definition)

Template References

Instead of a full definition, a node can reference a template:

{
    "BlockMesh": {
        "Template": "openFOAM.mesh.BlockMesh.jsonForm"
    }
}

The template path maps to a file in hermes/Resources/: openFOAM.mesh.BlockMesh.jsonForm → hermes/Resources/openFOAM/mesh/BlockMesh/jsonForm.json

GUI Configuration (react-jsonschema-form)

The GUI section follows the react-jsonschema-form specification:

Schema

JSON Schema defining the form fields:

{
    "Schema": {
        "type": "object",
        "properties": {
            "velocity": {
                "type": "number",
                "title": "Inlet Velocity",
                "default": 10.0
            },
            "viscosity": {
                "type": "number",
                "title": "Kinematic Viscosity",
                "default": 1e-06
            }
        }
    }
}

uiSchema

Controls how form fields are rendered:

{
    "uiSchema": {
        "velocity": {
            "ui:widget": "updown"
        },
        "viscosity": {
            "ui:widget": "text"
        }
    }
}

formData

Default values for the form:

{
    "formData": {
        "velocity": 10.0,
        "viscosity": 1e-06
    }
}

Parameter References

Parameters can reference outputs from other nodes:

Pattern	Description
{NodeName.output.Field}	Reference a specific output field
{NodeName.output}	Reference the entire output object
{workflow.field}	Reference a workflow-level field

Special Syntax

Syntax	Description
{}	Empty parameter (interpreted as empty object)
#{expression}	OpenFOAM #calc expression (preserved in output)

Complete Example

{
    "workflow": {
        "root": null,
        "nodeList": [
            "Parameters",
            "CopyDirectory",
            "BlockMesh",
            "ControlDict",
            "FilesWriter"
        ],
        "nodes": {
            "Parameters": {
                "type": "general.Parameters",
                "Execution": {
                    "input_parameters": {
                        "OFversion": "10",
                        "targetDirectory": "myCase"
                    }
                }
            },
            "CopyDirectory": {
                "type": "general.CopyDirectory",
                "Execution": {
                    "input_parameters": {
                        "Source": "templateCase",
                        "Target": "{Parameters.output.targetDirectory}"
                    }
                }
            },
            "BlockMesh": {
                "Template": "openFOAM.mesh.BlockMesh.jsonForm"
            },
            "ControlDict": {
                "Template": "openFOAM.system.ControlDict.jsonForm"
            },
            "FilesWriter": {
                "type": "general.FilesWriter",
                "Execution": {
                    "input_parameters": {
                        "Files": [
                            {
                                "Path": "{Parameters.output.targetDirectory}/system/blockMeshDict",
                                "Content": "{BlockMesh.output.Result}"
                            },
                            {
                                "Path": "{Parameters.output.targetDirectory}/system/controlDict",
                                "Content": "{ControlDict.output.Result}"
                            }
                        ]
                    }
                },
                "requires": ["CopyDirectory"]
            }
        }
    }
}