Steps

{
    "version": 2,
    "steps": [
        {
            "type": "procedure",
            "basePrice": "$.listPrice",
            "resultPrice": "$.unitPrice",
            "procedure": {
                "type": "MULT",
                "round": "item",
                "roundTo": 4,
                "items": [
                    {
                        "calculationType": "structural"
                    },
                    {
                        "calculationType": "contract"
                    },
                    {
                        "type": "MAX",
                        "items": [
                            {
                                "calculationType": "season"
                            },
                            {
                                "calculationType": "promo_percent"
                            }
                        ]
                    }
                ]
            }
        },
        {
            "type": "setValue",
            "object": "orders__DeliveryLineItem__c",
            "resultPrice": "$.unitPrice",
            "condition": {
                "operator": "AND",
                "items": [
                    {
                        "field": "$.unitPrice",
                        "operator": "less",
                        "value": 0
                    }
                ]
            },
            "value": 0
        },
        {
            "type": "rollUp",
            "baseObject": "orders__DeliveryLineItem__c",
            "basePrice": "$.unitPrice",
            "method": "copyEqual",
            "result": [
                {
                    "resultObject": "orders__OrderLineItem__c",
                    "resultPrice": "$.unitPrice"
                }
            ]
        },
        {
            "type": "setValue",
            "object": "orders__DeliveryLineItem__c",
            "resultPrice": "$.totalPrice",
            "value": {
                "operator": "multi",
                "items": [
                    "$.unitPrice",
                    "$.quantity"
                ]
            }
        },
        {
            "type": "rollUp",
            "baseObject": "orders__DeliveryLineItem__c",
            "basePrice": "$.totalPrice",
            "method": "sum",
            "result": [
                {
                    "resultObject": "orders__Order__c",
                    "resultPrice": "$.totalPrice"
                },
                {
                    "resultObject": "orders__Delivery__c",
                    "resultPrice": "$.totalPrice"
                },
                {
                    "resultObject": "orders__OrderLineItem__c",
                    "resultPrice": "$.totalPrice"
                }
            ]
        },
        {
            "type": "setValue",
            "object": "orders__DeliveryLineItem__c",
            "resultPrice": "$.totalDiscount",
            "value": {
                "operator": "multi",
                "items": [
                    {
                        "operator": "sum",
                        "items": [
                            "$.listPrice",
                            "- $.unitPrice"
                        ]
                    },
                    "$.quantity"
                ]
            }
        },
        {
            "type": "rollUp",
            "baseObject": "orders__DeliveryLineItem__c",
            "basePrice": "$.totalDiscount",
            "method": "sum",
            "result": [
                {
                    "resultObject": "orders__Order__c",
                    "resultPrice": "$.totalDiscount"
                },
                {
                    "resultObject": "orders__Delivery__c",
                    "resultPrice": "$.totalDiscount"
                },
                {
                    "resultObject": "orders__OrderLineItem__c",
                    "resultPrice": "$.totalDiscount"
                }
            ]
        }
    ]
}

{
  "version": "value",
  "steps": [
    {
      "type": "procedure"   // beginning of the first step;
      "basePrice": "$.listPrice",   // the name of the field for the actual price source;
      "resultPrice": "$.unitPrice",   // the name of the field for the calculation end results;
      "procedure": {   // beginning of the procedure within the first step;
      "type"(operation type):"value",   // MIN or MAX or MULT or SUM
      "round":"value",   // "item" or "group"
      "roundTo":"value",   // the number of decimals
      "items": [   // an array of the calculated discounts;
        {
          "calculationType":"external id of the discount 1"
        },
        {
          "calculationType":"external id of the discount 2"
        }
      ]
    }
  }
 ]
}