What does HRX mean at the start of a DBI name?

Summary:

Some DBIs start with the letters HRX, what does that mean?

Content (please ensure you mask any confidential information):

When writing payroll fast formulas, the DBIs we use usually start with PER, PAY, ABS, BEN, which clearly indicate which module they are querying.

There are also DBIs the start with HRX_{countrycode} like HRX_GB.

What are these, and can they be used within payroll fast formulas? The one I'm particularly looking at is HRX_GB_GPGAP_MIN_ASG_START_DATE which appears to give the assignment start date, something that seems to be completely missing from the PER DBIs.