Update README.md

Author: jason-fox

README.md

@@ -244,6 +244,19 @@ creating two new entities (stores in **Berlin**). Any entity must have a `id` an
 attributes are optional and will depend on the system being described. Each additional attribute should also have a
 defined `type` and a `value` attribute.
 
+> [!NOTE]
+> The `type` attribute should be used to describe the **Datatype**  of the Entity and its Properties
+> 
+> -  For Native JSON Properties, the `type` can align with a well-known  **Datatype** schema, such as [schema.org](https://schema.org/DataType)  or
+>    [XML Schema](https://www.w3.org/TR/2004/REC-xmlschema-2-20041028/) - typically values such as: `Time`, `Boolean`, `DateTime`, `Number`,
+>    `Text`, `Date`, `Float`, `Integer` etc.
+> -  For other JSON Objects, where possible use a datatype from an existing ontology - for example `PostalAddress` aligns with `https://schema.org/PostalAddress`.
+> -  `"type": "Property"` can also be used if maintenance of a detailed datatype is not important.
+> -  For GeoProperties, define the position using [GeoJSON](https://geojson.org/) and use the attribute type: `"type": "geo:json"`
+> -  Use of [NGSI-LD](https://ngsi-ld-tutorials.readthedocs.io/) Property sub-classes such `LanguageProperty`, `VocabularyProperty`, `JsonProperty` and `ListProperty`
+>    can be useful if it is enviaged that an NGSI-v2 system is expected to later connect with NGSI-LD systems for Federations and Data Spaces
+> -  By convention `"type": "Relationship"` is used for [Relationships](https://github.com/FIWARE/tutorials.Entity-Relationships/tree/NGSI-v2)
+
 #### 2️⃣ Request:
 
 ```console