Software Engineering: Function Point Analysis: Transactional FPs

Each screen, form, dialog box, report, or diagram corresponds to one (or more if it performs more than one function) EI, EO, or EQ, if it also references at least one file and performs one function.

External Inputs (EI)

External input is an "elementary process that processes data or control information that enters from outside the boundary of the application." The data may alter an ILF and/or alter the behavior of the system. Control information must have a business meaning (eg, not navigation actions, not login or startup operations, not refreshing, not clicking to move data, ...).

Complexity of each EI is computed from

• Data Element Types (DETs). (Computed differently than for EIFs and ILFs).
  • Count one DET for each non-repeated, user-recognizable field that enters or exits the boundary of the application.
  • Count only one DET for multiple fields that the user would regard as one piece of information (eg, a name or an address).
  • Count only one DET for the possibility of an error message, confirmation request, or verification, regardless of how many of these there are for this EI.
  • Count only one DET, even if there are multiple interface ways of invoking an action (menu, button, function key, ...).
• File Types Referenced (FTRs) is total number of ILFs and EIFs read or written by the EI.

External Outputs. (EO)

"An External Output (EO) is an elementary process that generates data or control information that exits the boundary of the application." There must be processing logic which contains at least one calculation, creates derived data, maintains one or more ILFs, or alters the system in some way. Rearranging, sorting, or reformatting data is not considered an EO, neither are error messages or confirmations considered an EO.

Complexity measurement requires computing DET and FTR values.

• DETs (Data Element Types) are computed as
  • One for each field that enters the application to specify what is to be done. Only count one regardless of how large the value is (eg, many paragraphs of text).
  • One for every field that exits the application. If a value enters and exits, count it only once.
  • One for capability of giving error message, confirmation, or verification.
  • Count one for each graphical label and value. Eg, a pie chart slice gets 2 DETs - one for the label and one for the percentage representation.
  • Count as only one DET multiple fields the user considers one (eg, an address).
  • Do not count page information, positioning information, date/time stamps, buttons, literals, titles, column headings, field titles.
• FTRs (File Types Referenced). Count as for EI.

External Inquiries. (EQ)

External Inquires (EQ) simply present data from an ILF or EIF without calculation or changing an ILF. For example, viewing or browsing data or reading email would be an EQ. In addition, using list boxes or pointing and clicking on something to return unprocessed data is an EI.
Complexity. Count DETs and FTRs as for the EO. Use the same complexity matrix as EO.

Complexity matrixes

EI Complexity DETs FTRs 1-4 5-15 >15 <2 Low Low Avg 2 Low Avg High >2 Avg High High

EO and EQ Complexity DETs FTRs 1-5 6-19 >19 <2 Low Low Avg 2-3 Low Avg High >3 Avg High High