Indirect PI point references

You can configure a PI point data reference to point at another attribute. The referenced attribute must itself be a PI point data reference. This is called an indirect reference to whatever PI point the target attribute references. It makes sense to reference by attribute when you need multiple attributes that each use data from the same PI point.

For example, suppose you have an attribute called Level that references a PI point registering a tank level. You want three child attributes to hold the daily average, minimum, and maximum tank levels. If you configure the three child attributes to reference the Level attribute, you can later change the Level attribute to reference a different point and you do not have to reconfigure child attributes. Used in combination with templates, this significantly reduces the amount of configuration required per element instance.

Relative paths

To reference another attribute, the configuration string uses a relative path. The relative path identifies a data reference attribute based on its name and its place in the hierarchy of elements and attributes. For the PI point data reference, the path must include an attribute path designation (| or ..) in the configuration string so that it is distinguished from a PI point reference.

The following table shows typical configurations for indirect references: