Many implementations will not be able to represent the full range of DateTime values. To maximize interoperability, the following rules apply:

When going from XML to an implementation:

If the XML value is <= MinDate then the value is MinDate;

If the XML value is >= MaxDate then the value is MaxDate;

XML values without a TimezoneOffset are assumed to be in UTC;

XML values with a TimezoneOffset are converted to UTC;

Fractions of seconds not supported by the implementation are dropped.

When going from an implementation to XML:

If the value is MinDate the XML is ‘0001-01-01T00:00:00Z’;

If the value is MaxDate the XML is ‘9999-12-31T23:59:59Z’;

XML values are always in UTC;

Fractions of seconds, if supported by the implementation, are included.

Where:

MinDate is the earliest date supported by an implementation;

MaxDate is the latest date supported by an implementation;

All implementations are required to support seconds.

The value of MinDate is the default value and semantically equivalent to a Null value.

XML has two ByteString representations – hexBinary and base64Binary. The mapping of OPC UA ByteString to XML base64Binary is defined in OPC 10000-6. The mapping to XML hexBinary is defined in section 5.4.

Implementations might limit the maximum ByteString size.

Implementations might limit the maximum String size.

In OPC UA, limitations on the string are only defined in the specification but not explicitly defined by the data structure, so implementations not following the specification may provide invalid values.

Both data types are based on strings defined in IETF RFC 5646 and should represent the same format, e.g., “en-US”.

OPC UA allows an empty or null string, which is not allowed in XML.

In OPC UA, limitations on the string are only defined in the specification but not explicitly defined by the data structure, so implementations not following the specification may provide invalid values.

In XML, the schema definition only restricts the allowed values to a certain degree, so implementations not following the specification may provide invalid values.

XML only restricts the allowed values to a certain degree in its schema definition, so potentially values could be invalid.