Question concerning If-Attribute.

I use If-Source-Attribute and If-Operation-Attribute and have ran into
If-Attribute.

It appears If-Attribute will query the source data store if an operation
attribute is not available? If an operation attribute is available it will
use that?

Does this mean that If-Attribute will not check the source, if an
operational attribute is present? Will it depend on an operational attribute
being added or removed?