All OPC UA DataEncodingsare based on rules that are defined for a standard set of built-in types. These built-in types are then used to construct structures, arrays and Messages. The built-in types are described in Table 1.

Table 1– Built-in Data Types

ID

Name

Description

1

Boolean

A two-state logical value (true or false).

2

SByte

An integer value between −128 and 127 inclusive.

3

Byte

An integer value between 0 and 255 inclusive.

4

Int16

An integer value between −32 768 and 32 767 inclusive.

5

UInt16

An integer value between 0 and 65 535 inclusive.

6

Int32

An integer value between −2 147 483 648 and 2 147 483 647 inclusive.

7

UInt32

An integer value between 0 and 4 294 967 295 inclusive.

8

Int64

An integer value between −9 223 372 036 854 775 808 and 9 223 372 036 854 775 807 inclusive.

9

UInt64

An integer value between 0 and 18 446 744 073 709 551 615 inclusive.

10

Float

An IEEE single precision (32 bit) floating point value.

11

Double

An IEEE double precision (64 bit) floating point value.

12

String

A sequence of Unicode characters.

13

DateTime

An instance in time.

14

Guid

A 16-byte value that can be used as a globally unique identifier.

15

ByteString

A sequence of octets.

16

XmlElement

An XML element.

17

NodeId

An identifier for a node in the address space of an OPC UA Server.

18

ExpandedNodeId

A NodeId that allows the namespace URI to be specified instead of an index.

19

StatusCode

A numeric identifier for an error or condition that is associated with a value or an operation.

20

QualifiedName

A name qualified by a namespace.

21

LocalizedText

Human readable text with an optional locale identifier.

22

ExtensionObject

A structure that contains an application specific data type that may not be recognized by the receiver.

23

DataValue

A data value with an associated status code and timestamps.

24

Variant

A union of all of the types specified above.

25

DiagnosticInfo

A structure that contains detailed error and diagnostic information associated with a StatusCode.

Most of these data types are the same as the abstract types defined in OPC 10000-3and OPC 10000-4. However, the ExtensionObjectand Varianttypes are defined in this standard. In addition, this standard defines a representation for the Guidtype defined in OPC 10000-3.