Although not required, a tag dictionary may contain tag groups. The Tag Group Definitions folder in a TagDictionary property
sheet contains the collection of TagGroups for that dictionary. A tag group provides a structure that lets you add multiple
tags to an object, with a single action. Typically tags are in a group because it is common for each of the tags to be assigned
to a single component.
For example, in the Haystack Tag Dictionary, there is a tag group for “discharge air temp sensor” that contains the following
set of individual tags:
- discharge
- air
- temp
- sensor
Once a tag group is applied to an object it implies all of the individual tags in its tag list, as well as implying a marker
tag that bears the name of the tag group. What this allows you to do is easily define a NEQL search for the marker tag for
that tag group rather than defining a search by concatenating each of the tags in the tag group’s tag list.
The Device Manager and Point Manager views of a driver, and the Edit Tags dialog are the primary methods for adding a Tag Group to a component.
NOTE: When creating or editing a Tag Group, a tagging best practice is to include only those tags that have a corresponding Tag
Definition in the parent tag dictionary. One way to guarantee it is to populate the Tag Group’s Tag List with tags copied
only from the Tag Definitions list in the tag dictionary. Note that in
Niagara 4.0, any tag that exists in a Tag Group Definition is required to have a corresponding Tag Definition in the same tag dictionary. While in
Niagara 4.1 this is no longer required but it is still a recommended best practice.
TagGroup functionality changes for
Niagara 4.1
Starting in
Niagara 4.1, when using the
Edit Tags dialog to add a Tag Group, the Tag Group displays in the
Direct Tags tab as an Ord to the Tag Group itself, and once the change is saved the individual tags of the Tag Group display in the
Implied Tags tab. This is a change from how Tag Group tags were handled in
Niagara 4.0, where using the
Edit Tags dialog to add a Tag Group resulted in the individual tags displaying in the
Direct Tags tab.
A Tag Group can contain tags from other tag dictionaries. You can add a tag to a Tag Group that overrides the namespace of
the parent tag dictionary. This allows you to define a Tag Group that contains tags from multiple tag dictionaries. Note,
that
NOTE: There is no verification that a tag name entered in the Add Tag dialog is actually defined in a tag dictionary. If the Tag Definition does not exist, the added tag is an "ad hoc" tag. It
is possible to use ad hoc tags although, a tagging best practice is to include only those tags that have a corresponding Tag
Definition in the parent tag dictionary.
You can add a single “Data Policy” to a Tag Group Definitions folder (or to a Tag Definitions folder). A data policy provides
additional metadata that can be associated with a tagged component. For more details see “Data Policies”.
TagGroup properties
| Type |
Value |
Description |
| Validity |
|
Specifies criteria to be met in order for this tag group to be applied to an object. |
| TagInfoList |
|
Contains the collection of tags that make up this tag group. |