Transactional functional point deals with data in motion. External users or systems interact with the application being counted through various transactional functions that bring data from outside the system boundary into application data files being maintained within the application boundary. Or, these transactional functions may move data from within the application boundary to a user or system outside the application boundary. These transactional functions may use, create, update data from files maintained within the application boundary (ILF). They may also use or reference data from files that are maintained outside the application boundary (EIF). There are three types of transactional functions – External Input (EI), External Output (EO) and External Query (EQ).
External Inputs (EIs) are elementary
processes that bring data from outside the application boundary to files
within the application boundary and will essentially maintain one or
more Internal Logical Files (ILFs). During the transaction, these
elementary processes may read (not maintain) one or more ILFs and/or
EIFs.
While both External Outputs (EOs) and External Queries (EQs)
are elementary processes that send data or control information outside
the application boundary there is little difference in the way the data
for these elementary processes are created. EQs fetch data or control
information from ILFs or EIFs and present to the external users or
systems and do not involve any mathematical formulae or calculation,
create derived data or update any ILFs. In case of EOs, mathematical
formulas or calculations are used to prepare data for the external users
or systems. In addition to creating derived data Eos may maintain one
or more ILFs or alter the behavior of the system. For example, report
for displaying transactions within the current month from a bank account
will be an EQ whereas projection of interest at the end of the
financial year on current account balance will be and EO.
While some text may seem repetitive but these are important considerations when we discuss counting rules for EI, EO or EQ.
