Overview of tag naming conventions

The Tag attribute is the unique name of a point. The Tag attribute appears as "Name" in some applications, such as PI SMT and PI Builder.

When naming points, use a consistent, meaningful convention.

The Tag attribute can be any length and can include letters, numbers, and spaces. It has the following constraints:

• The first character can be alphanumeric, an underscore (_), or a percent sign (%).

  Note: Avoid using the underscore (_) and percent sign (%) characters in the Tag attribute, as some applications use them in special ways. For example, SQL uses these characters as wild cards.

• Control characters, such as linefeeds or tabs, are not allowed.

• The following characters are not allowed:

  * ? ; { } [ ] | \ ` ' "

  Note: Although commas ( , ) are allowed, using them in tags is not advised.

These restrictions do not apply to other tag attributes, such as the descriptor.

Some functions and components restrict tag length. PI SQL Subsystem (pisqlss) can process tags with up to 1,016 characters. Joins involving longer tags return no row found. Queries without joins return rows but truncate tags to 1,016 characters. For more information about PI SQL Subsystem, see pisqlss.