3 Terms, definitions and conventions

3.1 Overview

It is assumed that basic concepts of OPC UA information modelling are understood in this specification. This specification will use these concepts to describe the PackML object models. The concepts and terms used to describe the OPC UA information models are defined in other parts and listed in the following sections. Note that OPC UA terms and terms defined in this standard are italicized in the specification.

3.2 OPC 10000-1 terms

The following terms defined in OPC 10000-1 apply.

  1. AddressSpace

  2. Attribute

  3. Client

  4. Message

  5. Node

  6. NodeClass

  7. Object

  8. ObjectType

  9. Profile

  10. Reference

  11. ReferenceType

  12. Server

  13. Variable

  14. View

3.3 OPC 10000-3 terms

The following terms defined in OPC 10000-3 apply.

  1. Hierarchical Reference

  2. InstanceDeclaration

  3. ModellingRule

  4. OptionalPlaceholder

  5. MandatoryPlaceholder

  6. DataVariable

  7. Property

  8. SourceNode

  9. TargetNode

  10. TypeDefinitionNode

  11. VariableType

3.4 OPC 10000-8

The following terms defined in OPC 10000-8 apply.

  1. AnalogItem

  2. EngineeringUnits

3.5 OPC 10000-9

The following term defined in OPC 10000-9 apply.

  1. Operator

3.6 OPC UA PackML Terms

3.6.1 PackML<Term>

3.6.1.1 General

This standard adopts adding a PackML prefix to all PackML defined terms that are used in this standard that are also defined by OPC. The <Term> is the terminology defined by PackML. This allows the terminology used in PackML to be easily distinguished from terminology defined in OPC UA.

3.6.1.2 PackMLUnit

a concept that defines a collection of associated modules that can carry out one or more major processing activities.

3.6.1.3 PackMLTag

a concept that represents named data element that is used to command, read status, or provide administration of a unit.

3.6.1.4 PackMLStateModel

a concept that represents a state model of the operational state of a unit.

3.6.1.5 PackMLMode

a concept that represents the mode of operation of a unit, indicating which state model is currently active.

3.7 Abbreviations and symbols

DAData Access
ACAlarm and Condition
HAHistorical access
PLCProgrammable Logic Controllers
DCSDistributed Control Systems
OCSOpen Control Systems

3.8 OPC UA Notation

This standard uses the ModellingRules OptionalPlaceholder and MandatoryPlaceholder to define instance declarations, and defines a rule that the BrowseName of instance declarations having an OptionalPlaceholder or MandatoryPlaceholder ModellingRule be enclosed in angle brackets (<>). Originally, this rule is defined in OPC 10000-3 as a recommendation. This naming rule is also used in the description of a table. The BrowseName of a Node that has OptionalPlaceholder or MandatoryPlaceholder ModellingRule are described with angle brackets, which denotes that the name is not fixed. For example, BrowseName of Property is described as <PropertyName> in graphical notation and tables results in a Property that can have any name.