properties proposal

Example - properties/properties.ifcx

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+[
+//This is adding actual properties to an object (typical or occurance):
+{
+	"def": "over",
+	"name": "N2550...someobject",
+	"attributes": {
+		"properties": {
+			"a603490d-d91b-5ef6-826f-19619cf5cab7": 1.0,
+			"6275c351-4936-59d3-9fb5-f4590046e1b8": 10.0,
+			"a128307d-30ce-543d-bc22-7d011ef1869a": "REI30",
+			"196e8ff9-12a4-55dd-a9e5-efc84aca34b6": ["0.01","0.002","0.0015"],
+			"da796591-5082-5687-8808-70339adc2c98": 13
+		}
+},
+//Property definitions:
+{
+	//minumum required attributes
+	"def": "class",
+	"name": "a603490d-d91b-5ef6-826f-19619cf5cab7",
+	"type": "PropertyDefinition",
+	"attributes":{
+		"code": "bsi::ifc-core::5.1.0::IsExternal"
+	}
+},
+{
+	//example with extensive metadata
+	"def": "class",
+	"name": "6275c351-4936-59d3-9fb5-f4590046e1b8",
+	"type": "PropertyDefinition",
+	"attributes":{
+		"code": "bsi::ifc-core::5.1.0::NetVolume", 
+		//alternatively "code": "Volume", "source": "bsi::ifc-core::5.1.0", //optional
+		"displayName": {"pt-BR":"Volume Líquido","sv-SE":"Netto volym"},  //optional
+		"uri": "https://identifier.buildingsmart.org/uri/buildingsmart/ifc/4.3/prop/NetVolume", //optional
+		"dataType": "Real", //optional, one of: Boolean, Integer, Real, String, dateTime; default: Real
+		"measure": "Volume", //optional, which corresponds to "dimension": [3,0,0,0,0,0,0], and SI unit "cubic metre" with symbol "m³". Measure is a predefined set of dimensions, units and symbols. Other examples: {Weight, kilograms}, {SoundPower, Decibel}, {Productivity, PiecePerHour, ppm"}
+	}
+},
+{
+	//example with restrictions
+	"def": "class",
+	"name": "a128307d-30ce-543d-bc22-7d011ef1869a",
+	"type": "PropertyDefinition",
+	"attributes":{
+		"code": "bsi::ifc-core::5.1.0::FireRating",
+		"dataType": "String",
+		"enum": ["REI30","REI60","REI90","REI120"],  //has to comply with the dataType
+		//Alternative restrictions:
+		//"pattern": "ABC\\d*"       //regex
+		//"minInclusive": 3.0
+		//"maxInclusive": 3.0
+		//"minExclusive": 3.0
+		//"maxExclusive": 3.0
+	}
+},
+{
+	//example with list
+	"def": "class",
+	"name": "196e8ff9-12a4-55dd-a9e5-efc84aca34b6",
+	"type": "PropertyDefinition",
+	"attributes":{
+		"code": "bsi::ifc-elec::1.0.1::CurrentAdjustmentValues",
+		"valueKind": "List", //optional, default "Single" (IFCX does not have: Table, BoundedValue, Enumerated value, key-value pairs, complex or else...)
+		"measure": "ElectricCurrent", // dimension [0,0,-1,1,0,0,0], and unit "ampere" with symbol "A".
+	}
+},
+{
+	//example with custom property and unit
+	"def": "class",
+	"name": "da796591-5082-5687-8808-70339adc2c98",
+	"type": "PropertyDefinition",
+	"attributes":{
+		"code": "anycorp::ownprops::1.2.3::ProgressInMetresPerSquareMetre"
+		//That's it, the property is just any numeric value, without defined measure or unit. The unit is just reflected in the custom name.
+	}
+},
+//Definition of measures. This was debated in the group, and could instead be made implicit, covered by the standard.
+{
+	"def": "class",
+	"name": "Volume",	//or UUID
+	"type": "Measure",
+	"attributes":{
+		"dimension": [3,0,0,0,0,0,0],
+		"unit": "cubic metre",
+		"dataType": "Real",
+		"symbol": "m³",
+		"minExclusive": 0.0
+	}
+},
+{
+	"def": "class",
+	"name": "ElectricCurrent",	//or UUID
+	"type": "Measure",
+	"attributes":{
+		"dimension": [0,0,-1,1,0,0,0],
+		"dataType": "Real",
+		"unit": "ampere",
+		"symbol": "A",
+		"alternativeUnits": {	//dangerous idea, as not all can be converted with a simple factor (example: decibel - uses log scale)
+			"mA": {
+				"name": "miliampere",
+				"conversion": 0.001
+			},
+			"kA": {
+				"name": "kiloampere",
+				"conversion": 1000
+			}
+		}
+	}
+}
+]

docs/README.md

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+# IFCX documentation
+
+## Identifiers
+- Each object in IFCX should be identified by an UUID. UUIDs are supposed to be generated based on namespace/name hashed using SHA-1. 
+- Example UUID: 'a42208f9-02b7-51e2-b471-27121510c673'
+
+## Properties
+- Property `dataType` must be one of 'Real', 'Boolean', 'Integer', 'String' or 'dateTime'.
+  - deafult `dataType` is 'Real'.
+  - The 'dateTime' format needs to be according to the ISO 8601 series, meaning: YYYY-MM-DDThh:mm:ssTZD. For example '2023-05-10', '2023-05-10T15:10:12Z' or '2023-05-10T15:10:12+02:00'.
+- Properties by default have no unit or measure (undefined). 
+  - Property can have a defined measure, such as Length or Volume
+  - The measure takes one of the values from the standard list.  
+  - Each measure has one standard unit assigned to it. In most cases the unit is comes from SI (example: metre) or common practice (example: decibel). 
+  - Unit conversion, for example from the SI metre to feet or centimetre, should be handled on the software side to make sure users see and work with the units they are comfortable with. In IFCX file, the properties with specified measures are always defined in the unit of that measure.
+
+## Materials