Details of Capabilities

In both reading and writing (GET and SET), tags are addressed using OPC-UA XML Syntax:
  • String NodeID form: "ns=4;s=Foo.Bar.Baz"
  • IntegerNodeID form: "ns=34;i=11902"
  • OpaqueNodeID form: ns=;g=<UUID>
  • BinaryNodeID form: ns=;g=<Base64 string>

If ns is omitted, namespace 0 is assumed: "s=Foo.Bar.Baz"

The value will be returned as a JSON string of the form:
{"val":<data>, "type":<typename>}

Only numeric and the STRING and DATE_TIME types are returned currently. Other data types are not supported and the value will be “UNKNOWN”.

The supported types are:
  • float
  • double
  • bool
  • byte
  • sbyte
  • int16
  • uint16
  • int32
  • uint32
  • int64
  • uint64
  • string
  • datetime

To be compatible with JSON style SET node refs (described below) the GET method will accept node refs starting with “/json?”. So the two node refs /json?ns=4;i=1900 and ns=4;i=1900 are equivalent.

The supported types in flat JSON and their corresponding versions in the OPC-UA specification are as follows:
Table 1. Supported Flat JSON Types and OPC-UA Equivalents
Flat JSONOPC-UA
boolboolean
int8sbyte
int16int16
int32int32
int64int64
uint8byte
uint16uint16
uint32uint32
uint64uint64
floatfloat
doubledouble
stringstring
datetimedatetime

The OPC-UA data quality status is processed and bad or uncertain data will be forwarded as a null value with the quality flag set to "0" to Time Series. The quality flag is set to "3" for good data.