{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Standard Flowsheet Format (SFF) v0.0.3",
  "description": "A standard, machine-readable representation of a process flowsheet designed for interoperability and data exchange across process simulators (BioSTEAM, SuperPro Designer, Aspen Plus, and others). 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, version, and techno-economic summary of the flowsheet.",
      "type": "object",
      "properties": {
        "sff_version": {
          "type": "string",
          "description": "Version of the SFF schema used, e.g., '0.0.3'."
        },
        "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": {
          "description": "The primary product(s) of the process. Accepts a single string or an array of strings for co-product processes.",
          "oneOf": [
            { "type": "string" },
            { "type": "array", "items": { "type": "string" } }
          ]
        },
        "feedstock": {
          "type": "string",
          "description": "The primary feedstock or raw material input to 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."
        },
        "relevant_patents": {
          "type": "array",
          "description": "Patents associated with this process, if any.",
          "items": {
            "type": "object",
            "properties": {
              "label": { "type": "string", "description": "Patent number or short label." },
              "url": { "type": "string", "description": "URL to the patent record." }
            },
            "required": ["label"]
          }
        },

        "annual_throughput_kg_yr": {
          "type": "number",
          "description": "Annual throughput of the main product stream (kg/yr)."
        },
        "total_purchase_cost_usd": {
          "type": "number",
          "description": "Total equipment purchase cost (USD)."
        },
        "DFC_usd": {
          "type": "number",
          "description": "Direct Fixed Capital — total installed plant cost (USD)."
        },
        "annual_revenue_usd": {
          "type": "number",
          "description": "Annual product revenue (USD/yr)."
        },
        "annual_operating_cost_usd": {
          "type": "number",
          "description": "Annual total operating cost (USD/yr)."
        },
        "annual_electricity_cost_usd": {
          "type": "number",
          "description": "Annual electricity cost (USD/yr)."
        },
        "annual_labor_cost_usd": {
          "type": "number",
          "description": "Annual labor cost (USD/yr)."
        },
        "annual_waste_treatment_usd": {
          "type": "number",
          "description": "Annual waste treatment and disposal cost (USD/yr)."
        },
        "gross_profit_usd": {
          "type": "number",
          "description": "Annual gross profit = revenue − OPEX (USD/yr)."
        },
        "net_profit_usd": {
          "type": "number",
          "description": "Annual net profit after taxes (USD/yr)."
        },
        "gross_margin_pct": {
          "type": "number",
          "description": "Gross margin as a percentage (%)."
        },
        "payback_period_years": {
          "type": "number",
          "description": "Simple payback period (years)."
        },
        "IRR_before_taxes_pct": {
          "type": "number",
          "description": "Internal Rate of Return before taxes (%)."
        },
        "IRR_after_taxes_pct": {
          "type": "number",
          "description": "Internal Rate of Return after taxes (%)."
        },
        "NPV_usd": {
          "type": "number",
          "description": "Net Present Value (USD)."
        },
        "ROI_pct": {
          "type": "number",
          "description": "Return on Investment (%)."
        },

        "is_batch_mode": {
          "type": "boolean",
          "description": "Whether the process is operated in batch mode (true) or continuous mode (false)."
        },
        "batch_time_s": {
          "type": "number",
          "description": "Batch cycle time or continuous operating time per period (seconds)."
        },
        "number_of_batches_per_year": {
          "type": "number",
          "description": "Number of batches produced per year."
        },
        "annual_operating_time_s": {
          "type": "number",
          "description": "Annual available operating time (seconds/yr)."
        },
        "batch_throughput_kg": {
          "type": "number",
          "description": "Throughput per batch (kg/batch) or per hour for continuous processes (kg/h)."
        }
      },
      "required": [
        "sff_version"
      ]
    },

    "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')."
          },
          "viz_label": {
            "type": "string",
            "description": "Human-readable display label for canvas visualization. Auto-populated from unit_type or id if absent. Separate from 'id' (machine-readable unique key)."
          },
          "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'). May be a URL pointing to the implementing class in source control."
          },
          "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."
          },
          "installed_costs": {
            "type": "object",
            "additionalProperties": { "type": "number" },
            "description": "Equipment installed (purchase + installation) cost results for this unit operation."
          },
          "utility_consumption_results": {
            "type": "object",
            "additionalProperties": { "type": "number" },
            "description": "Heating, cooling, and power utility demand results for this unit operation. Keys must refer to utility IDs declared in heat_utilities or power_utilities."
          },
          "utility_production_results": {
            "type": "object",
            "additionalProperties": { "type": "number" },
            "description": "Heating, cooling, and power utility production results for this unit operation. Keys must refer to utility IDs declared in heat_utilities or power_utilities."
          }
        },
        "required": [
          "id",
          "unit_type"
        ]
      }
    },

    "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. Use 'None' if this stream enters the process boundary (i.e., it is a feed with no upstream unit)."
          },
          "sink_unit_id": {
            "type": "string",
            "description": "The ID of the unit operation that this stream enters. Use 'None' if this stream exits the process boundary (i.e., it is a product or waste with no downstream unit)."
          },
          "stream_type": {
            "type": "string",
            "enum": ["feed", "product", "waste", "internal"],
            "description": "Semantic classification of the stream's role in the process. 'feed' = enters from outside the process boundary (raw material or utility input); 'product' = leaves as a saleable product; 'waste' = leaves as effluent, emissions, or non-saleable byproduct; 'internal' = flows between two units within the process."
          },
          "viz_label": {
            "type": "string",
            "description": "Human-readable display label for canvas visualization. Auto-populated from stream id if absent. Separate from 'id' (machine-readable unique key)."
          },
          "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",
            "description": "Purchase or sale price of the stream material.",
            "properties": {
              "value": { "type": "number" },
              "units": { "type": "string", "default": "$/kg" }
            }
          },
          "stream_properties": {
            "description": "Structured object specifying the bulk physical 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" },
                  "units": { "type": "string", "default": "K" }
                }
              },
              "pressure": {
                "type": "object",
                "properties": {
                  "value": { "type": "number" },
                  "units": { "type": "string", "default": "Pa" }
                }
              }
            },
            "required": [
              "total_mass_flow",
              "total_volumetric_flow",
              "temperature",
              "pressure"
            ]
          },
          "composition": {
            "description": "An array detailing the chemical composition of the stream. Each entry specifies the phase, component name (matching an id in the 'chemicals' array if present), and mole fraction within that phase.",
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "phase": {
                  "type": "string",
                  "description": "Phase of the component (e.g., 'l' for liquid, 'g' for gas, 's' for solid).",
                  "default": "l"
                },
                "component_name": { "type": "string" },
                "mol_fraction": {
                  "type": "number",
                  "minimum": 0,
                  "maximum": 1
                }
              },
              "required": ["component_name", "mol_fraction"]
            }
          }
        },
        "required": [
          "id",
          "source_unit_id",
          "sink_unit_id"
        ]
      }
    },

    "chemicals": {
      "description": "An array of all pure chemical species involved in this process flowsheet. Optional — omit if component identities are fully encoded in the composition arrays.",
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "A unique identifier for this chemical, used as 'component_name' in stream composition arrays."
          },
          "registry_id": {
            "type": "string",
            "description": "CAS number or SMILES string."
          }
        },
        "required": ["id", "registry_id"],
        "additionalProperties": true
      }
    },

    "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 be specified in 'other_utilities' instead.",
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "properties": {
            "type": "object",
            "description": "Physical and economic properties of this heating/cooling utility agent.",
            "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" }
                }
              }
            },
            "required": ["id", "temperature", "pressure"]
          },
          "composition": {
            "description": "An array detailing the chemical components of the heating or cooling utility agent.",
            "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_consumption_results' and 'utility_production_results' of unit operations."
          }
        },
        "required": ["properties", "units_for_utility_results"]
      }
    },

    "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 grid 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_consumption_results' and 'utility_production_results' of unit operations."
          }
        },
        "required": ["id", "units_for_utility_results"]
      }
    },

    "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": {
          "properties": {
            "type": "object",
            "description": "Physical and economic properties of this utility.",
            "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" }
                }
              },
              "units_for_utility_results": {
                "type": "string",
                "description": "Units (e.g., 'kg/h') for the values associated with this utility in unit operation utility results."
              }
            },
            "required": ["id"]
          },
          "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"]
            }
          }
        },
        "required": ["properties"]
      }
    }
  },

  "required": [
    "metadata",
    "units",
    "streams"
  ]
}