Annex F (normative) Information Model XML Schema ToC Previous

F.1 Overview ToC Previous Next

Information Model developers define standard AddressSpaces which are implemented by many Servers. There is a need for a standard syntax that Information Model developers can use to formally define their models in a form that can be read by a computer program. Annex F defines an XML-based schema for this purpose.

The XML Schema released with this version of the standards can be found here:

http://www.opcfoundation.org/UA/schemas/1.05/UANodeSet.xsd

NOTE The latest file that is compatible with this version of the standards can be found here:

http://opcfoundation.org/UA/2011/03/UANodeSet.xsd

The schema document is the formal definition. The description in Annex F only discusses details of the semantics that cannot be captured in the schema document. Types which are self-describing are not discussed.

This schema can also be used to serialize (i.e. import or export) an arbitrary set of Nodes in the Server Address Space. This serialized form can be used to save Server state for use by the Server later or to exchange with other applications (e.g. to support offline configuration by a Client).

This schema only defines a way to represent the structure of Nodes. It is not intended to represent the numerous semantic rules which are defined in other parts of the OPC UA specification. Consumers of data serialized with this schema need to handle inputs that conform to the schema, however, do not conform to the OPC UA specification because of one or more semantic rule violations.

There are cases where an Information Model defines Nodes such as standard Properties which can be attached to many different Nodes. These Nodes are represented in the UANodeSet as Nodes which are not a target of any reference that would make them visible in an AddressSpace.

The tables defining the DataTypes in the specification have field names starting with a lowercase letter. The first letter shall be converted to upper case when the field names are formally defined in a UANodeSet.

Every UANodeSet that defines DataTypes has associated schema files that define how to serialize the DataTypes using the UA Binary Encoding (5.2) and the UA XML Encoding (5.3). The XML schema file may be referenced by the UANodeSet if it includes Variable Values (F.8) for one or more of the DataTypes defined in the UANodeSet. The namespace URI assigned to the XML schema is set by the tool that generated it. The URI for the XML schema for OPC UA DataTypes is http://opcfoundation.org/UA/2008/02/Types.xsd.

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