AliasNameCategoryType instances are used to organize the AliasNameType instances that a Server defines. They can also include instances of AliasNameCategoryType to allow hierarchical groupings of AliasNames. It includes a mandatory Method for finding instances of AliasNameType in the AliasName hierarchy, starting at this instance of AliasNameCategoryType. For example, if the Method call is made on the Aliases AliasNameCategoryType instance (see 9.2), it would apply the AliasNameSearchPattern to all AliasNames that are defined under TagVariables, Topics and any other AliasNameCategoryType instance in the hierarchy.
The AliasNameCategoryType is a subtype of FolderType and is formally defined in Table 2.
Table 2 – AliasNameCategoryType Definition
|
Attribute |
Value |
||||
|
BrowseName |
AliasNameCategoryType |
||||
|
IsAbstract |
False |
||||
|
References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
|
Subtype of the FolderType from OPC 10000-5 |
|||||
|
Organizes |
Object |
<Alias> |
|
AliasNameType |
OptionalPlaceholder |
|
Organizes |
Object |
<SubAliasNameCategories> |
|
AliasNameCategoryType |
OptionalPlaceholder |
|
HasComponent |
Method |
FindAlias |
Defined in 6.3.2 |
Mandatory |
|
|
HasProperty |
Variable |
LastChange |
VersionTime |
PropertyType |
Optional |
|
Conformance Units |
|||||
|
AliasName Base |
|||||
The list of AliasNames that an Object contains may be dynamic. For example, AliasNames may be added in an aggregating Server as underlying Servers become available or may be removed if a Server is no longer available.
<Alias> represents any number of instances of AliasNameType. Each instance shall have at least one AliasFor Reference to a Node. Multiple <Alias > instances can point to the same Node.
<SubAliasNameCategories> allows the nesting or structuring of AliasNames into hierarchical groupings.
An <Alias> can appear in more than one place in the hierarchy of AliasNameCategories.
LastChange is the most recent time for any of the following activities:
- The last time an AliasName was added to or deleted from the AliasNameCategory,
- The last time an AliasNameCategory was added or deleted,
- The last time the referenced Nodes of an AliasName in the AliasNameCategory changed.
For AliasNameCategoryType instances that are nested, the value of LastChange shall always be the latest VersionTime of all Organized AliasName and AliasNameCategories.
The LastChange shall be persisted. A Client that detects a LastChange that is older than what it has cached, shall clear all cached AliasNameCategories and related AliasNames.