{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Standard Flowsheet Format (SFF)",
  "description": "A standardized, machine-readable representation of a process flowsheet designed for interoperability and data exchange. It represents the process as a directed graph with rich data attached to both nodes (units) and edges (streams).",
  "type": "object",
  "properties": {
    "metadata": {
      "description": "Information about the source, context, and version of the flowsheet.",
      "type": "object",
      "properties": {
        "sff_version": {
          "type": "string",
          "description": "Version of the SFF schema used, e.g., '1.0'."
        },
        "TEA_currency": {
          "type": "string",
          "description": "Currency used to report cost results.",
          "default": "USD"
        },
        "TEA_year": {
          "type": "number",
          "description": "TEA year used to report cost results."
        },
        "source_doi": {
          "type": "string",
          "description": "Digital Object Identifier (DOI) of the source publication, if any."
        },
        "product_name": {
          "type": "string",
          "description": "The primary product of the process."
        },
        "organism": {
          "type": "string",
          "description": "The organism used for production, if applicable."
        },
        "process_title": {
          "type": "string",
          "description": "A descriptive title for the process."
        },
        "flowsheet_designers": {
          "type": "string",
          "description": "Name(s) of the authors who designed this flowsheet."
        }
      },
      "required": [
        "sff_version",
        "TEA_year"
      ]
    },
    "units": {
      "description": "An array of all unit operations, representing the nodes of the process graph.",
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "A unique identifier for this unit operation."
          },
          "unit_type": {
            "type": "string",
            "description": "A short description of the type of unit operation (e.g., 'Distillation', 'Solids centrifugation')."
          },
          "design_input_specs": {
            "type": "object",
            "description": "Design input specifications for the unit operation. If provided, these specifications -- combined with the provided compositions of streams entering this unit operation and the method described in 'design_simulation_method' -- should be sufficient to generate all design results, cost results, utility results, and compositions of all streams effluent from this unit operation."
          },
          "design_simulation_method": {
            "type": "string",
            "description": "Design and simulation method for the unit operation, (e.g., for distillation, this could be 'McCabe-Thiele', 'Fenske-Underwood-Gilliland', or 'MESH'). If provided, this method -- combined with the provided 'design_input_specs' and compositions of streams entering this unit operation -- should be sufficient to generate all design results, cost results, utility results, and compositions of all streams effluent from this unit operation."
          },
          "thermo_property_package": {
            "type": "object",
            "description": "A thermodynamic property package, with qualitative descriptions of property estimation methods.",
            "properties": {
              "id": {
                "type": "string"
              },
              "mixture": {
                "type": "string",
                "description": "Method for computing mixture properties (e.g., 'ideal mixture').",
                "default": "Ideal"
              },
              "gamma": {
                "type": "string",
                "description": "Method for computing activity coefficients (e.g., 'UNIFAC').",
                "default": "Ideal"
              },
              "phi": {
                "type": "string",
                "description": "Method for computing fugacity coefficients (e.g., 'Ideal').",
                "default": "Ideal"
              },
              "PCF": {
                "type": "string",
                "description": "Method for computing Poynting correction factors (e.g., 'None').",
                "default": "None"
              }
            },
            "additionalProperties": {
              "type": "string"
            }
          },
          "reactions": {
            "type": "array",
            "description": "Reactions occurring in this unit operation, each with the index (determining the order in which reactions occur, with identical index for parallel reactions), conversion, and the reactant for conversion.",
            "items": {
              "type": "object",
              "properties": {
                "index": {
                  "type": "integer"
                },
                "equation": {
                  "type": "string"
                },
                "reactant": {
                  "type": "string"
                },
                "conversion": {
                  "type": "number"
                }
              }
            }
          },
          "design_results": {
            "type": "object",
            "additionalProperties": {
              "type": "number"
            },
            "description": "Design results for this unit operation. This object, combined with design_input_specs, should provide a full design description for this unit operation (to the highest level of detail modeled)."
          },
          "purchase_costs": {
            "type": "object",
            "additionalProperties": {
              "type": "number"
            },
            "description": "Equipment purchase cost results for this unit operation. These may be for the entire unit operation or for individual unit operations (depending on the level of detail modeled)."
          },
          "installed_costs": {
            "type": "object",
            "additionalProperties": {
              "type": "number"
            },
            "description": "Equipment installed (purchase + installation) cost results for this unit operation. These may be for the entire unit operation or for individual unit operations (depending on the level of detail modeled)."
          },
          "utility_consumption_results": {
            "type": "object",
            "additionalProperties": {
              "type": "number"
            },
            "description": "Heating, cooling, and power utility demand results for this unit operation. These must refer to the same utility IDs as those detailed in the heat_utilities or power_utilities properties for this flowsheet."
          },
          "utility_production_results": {
            "type": "object",
            "additionalProperties": {
              "type": "number"
            },
            "description": "Heating, cooling, and power utility production results for this unit operation. These must refer to the same utility IDs as those detailed in the heat_utilities or power_utilities properties for this flowsheet."
          }
        },
        "required": [
          "id",
          "unit_type"
        ],
        "additionalProperties": false
      }
    },
    "streams": {
      "description": "An array of process streams that connect the units, representing the edges of the process graph.",
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "A unique identifier for this stream."
          },
          "source_unit_id": {
            "type": "string",
            "description": "The ID of the unit operation from which this stream originates."
          },
          "sink_unit_id": {
            "type": "string",
            "description": "The ID of the unit operation that this stream enters."
          },
          "stream_description": {
            "type": "string",
            "description": "A qualitative description of the stream from the perspective of either the source (e.g., 'Centrifugate') or sink unit operation (e.g., 'Make-up solvent')."
          },
          "price": {
            "type": "object",
            "properties": {
              "value": {
                "type": "number"
              },
              "units": {
                "type": "string",
                "default": "$/kg"
              }
            }
          },
          "stream_properties": {
            "description": "Structured object specifying the properties of the stream.",
            "type": "object",
            "properties": {
              "total_mass_flow": {
                "type": "object",
                "properties": {
                  "value": {
                    "type": "number"
                  },
                  "units": {
                    "type": "string",
                    "default": "kg/h"
                  }
                }
              },
              "total_volumetric_flow": {
                "type": "object",
                "properties": {
                  "value": {
                    "type": "number"
                  },
                  "units": {
                    "type": "string",
                    "default": "m3/h"
                  }
                }
              },
              "total_molar_flow": {
                "type": "object",
                "properties": {
                  "value": {
                    "type": "number"
                  },
                  "units": {
                    "type": "string",
                    "default": "kmol/h"
                  }
                }
              },
              "temperature": {
                "type": "object",
                "properties": {
                  "value": {
                    "type": "number",
                    "minimum": 0
                  },
                  "units": {
                    "type": "string",
                    "default": "K"
                  }
                }
              },
              "pressure": {
                "type": "object",
                "properties": {
                  "value": {
                    "type": "number"
                  },
                  "units": {
                    "type": "string",
                    "default": "Pa"
                  }
                }
              },
              "composition": {
                "description": "An array detailing the chemical components of the stream.",
                "type": "array",
                "items": {
                  "type": "object",
                  "properties": {
                    "phase": {
                      "type": "string",
                      "default": "l"
                    },
                    "component_name": {
                      "type": "string"
                    },
                    "mol_fraction": {
                      "type": "number",
                      "minimum": 0,
                      "maximum": 1
                    }
                  },
                  "required": [
                    "component_name",
                    "mol_fraction"
                  ]
                }
              }
            },
            "required": [
              "total_mass_flow",
              "total_volumetric_flow",
              "temperature",
              "pressure"
            ]
          }
        },
        "required": [
          "id",
          "source_unit_id",
          "sink_unit_id"
        ]
      }
    },
    "chemicals": {
      "description": "An array of all chemicals involved in this process flowsheet.",
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "A unique identifier for this chemical, used in the 'composition' property of stream objects."
          },
          "registry_id": {
            "type": "string",
            "description": "CAS number or SMILES string."
          }
        },
        "required": [
          "id",
          "registry_id"
        ],
        "additionalProperties": true
      }
    },
    "utilities": {
        "description": "An array of all heating, cooling, power, and other utility types involved in this flowsheet.",
        "type": "object",
        "properties": {
            "heat_utilities": {
              "description": "An array of all heating and cooling utility types involved in this process flowsheet. Combustion-based utility types (e.g., natural gas) should not be specified here and should instead be specified in 'other_utilities'.",
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "id": {
                    "type": "string",
                    "description": "A unique identifier for this utility type (e.g., high-pressure steam)."
                  },
                  "temperature": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number"
                      },
                      "units": {
                        "type": "string",
                        "default": "K"
                      }
                    }
                  },
                  "pressure": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number"
                      },
                      "units": {
                        "type": "string",
                        "default": "Pa"
                      }
                    }
                  },
                  "regeneration_price": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number",
                        "default": 0
                      },
                      "units": {
                        "type": "string",
                        "default": "$/kmol"
                      }
                    }
                  },
                  "heat_transfer_price": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number",
                        "default": 0
                      },
                      "units": {
                        "type": "string",
                        "default": "$/kJ"
                      }
                    }
                  },
                  "heat_transfer_efficiency": {
                    "type": "number",
                    "default": 1
                  },
                  "temperature_limit": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number"
                      },
                      "units": {
                        "type": "string",
                        "default": "K"
                      }
                    }
                  },
                  "composition": {
                    "description": "An array detailing the chemical components of the heating or cooling utility.",
                    "type": "array",
                    "items": {
                      "type": "object",
                      "properties": {
                        "phase": {
                          "type": "string",
                          "default": "l"
                        },
                        "component_name": {
                          "type": "string"
                        },
                        "mol_fraction": {
                          "type": "number",
                          "minimum": 0,
                          "maximum": 1
                        }
                      },
                      "required": [
                        "component_name",
                        "mol_fraction"
                      ]
                    }
                  },
                  "units_for_utility_results": {
                    "type": "string",
                    "description": "Units (e.g., 'kJ/h') for the values associated with this utility in the 'utility_results' of unit operations in this flowsheet."
                  }
                },
                "required": [
                  "id",
                  "temperature",
                  "pressure",
                  "composition",
                  "units_for_utility_results"
                ],
                "additionalProperties": false
              }
            },
            "power_utilities": {
              "description": "An array of all power utility types involved in this process flowsheet.",
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "id": {
                    "type": "string",
                    "description": "A unique identifier for this power utility type (e.g., 'marginal electricity')."
                  },
                  "price": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number",
                        "default": 0
                      },
                      "units": {
                        "type": "string",
                        "default": "$/kWh"
                      }
                    }
                  },
                  "units_for_utility_results": {
                    "type": "string",
                    "description": "Units (e.g., 'kW') for the values associated with this utility in the 'utility_results' of unit operations in this flowsheet."
                  }
                },
                "required": [
                  "id",
                  "units_for_utility_results"
                ],
                "additionalProperties": {
                  "type": "number"
                }
              }
            },
            "other_utilities": {
              "description": "An array of all other utility types involved in this process flowsheet. Combustion-based utility types (e.g., natural gas) may be specified here.",
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "id": {
                    "type": "string",
                    "description": "A unique identifier for this utility type (e.g., natural gas)."
                  },
                  "temperature": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number"
                      },
                      "units": {
                        "type": "string",
                        "default": "K"
                      }
                    }
                  },
                  "pressure": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number"
                      },
                      "units": {
                        "type": "string",
                        "default": "Pa"
                      }
                    }
                  },
                  "price": {
                    "type": "object",
                    "properties": {
                      "value": {
                        "type": "number",
                        "default": 0
                      },
                      "units": {
                        "type": "string",
                        "default": "$/kg"
                      }
                    }
                  },
                  "composition": {
                    "description": "An array detailing the chemical components of the utility.",
                    "type": "array",
                    "items": {
                      "type": "object",
                      "properties": {
                        "phase": {
                          "type": "string",
                          "default": "l"
                        },
                        "component_name": {
                          "type": "string"
                        },
                        "mol_fraction": {
                          "type": "number",
                          "minimum": 0,
                          "maximum": 1
                        }
                      },
                      "required": [
                        "component_name",
                        "mol_fraction"
                      ]
                    }
                  },
                  "units_for_utility_results": {
                    "type": "string",
                    "description": "Units (e.g., 'kg/h') for the values associated with this utility in the 'utility_results' of unit operations in this flowsheet."
                  }
                },
                "required": [
                  "id",
                  "temperature",
                  "pressure",
                  "composition",
                  "units_for_utility_results"
                ],
                "additionalProperties": false
              }
            }
    }
  }
},
  "required": [
    "metadata",
    "units",
    "streams",
    "utilities"
  ]
}