scalar holds scalar data under a single generic container. The semantics are usually resolved by linking to a dictionary. scalar defaults to a scalar string but has attributes which affect the type.

scalar does not necessarily reflect a physical object (for which object should be used). It may reflect a property of an object such as temperature, size, etc.

Note that normal Schema validation tools cannot validate the data type of scalar (it is defined as string), but that a temporary schema can be constructed from the type and used for validation. Also the type can be contained in a dictionary and software could decide to retrieve this and use it for validation.