| Role (v. 1.0) | Example |
|---|---|
| Fixed value | maxStringLength |
| Stepper | count |
| Most-recent holder | inputData |
| Most-wanted holder | maximum |
| Gatherer | sum |
| Follower | prev |
| One-way flag | errorsOccurred |
| Temporary | temp |
| Organizer | sortArray |
Later (Ben-Ari, Sajaniemi; 2004) a tenth role, transformation, was added to cover cases where a variable is obtained by some calculation from other variables (v. 1.1).
Surveys in three programming paradigms -- OO, procedural and functional -- (Sajaniemi, Ben-Ari, Byckling, Gerdt, Kulikova; submitted) revealed that data structures needed two more roles and that the role of transformation is actually a special case of temporary (or in other case of some other role). Thus the new set consists of 11 roles (green for all variables, blue for data structure use):
| Role (v. 2.0) | Example | Informal definition |
|---|---|---|
| Fixed value | maxStringLength | A data item that does not get a new proper value after its initialization |
| Stepper | count | A data item stepping through a systematic, predictable succession of values |
| Most-recent holder | inputData | A data item holding the latest value encountered in going through a succession of unpredictable values, or simply the latest value obtained as input |
| Most-wanted holder | maximum | A data item holding the best or otherwise most appropriate value encountered so far |
| Gatherer | sum | A data item accumulating the effect of individual values |
| Follower | prev | A data item that gets its new value always from the old value of some other data item |
| One-way flag | errorsOccurred | A two-valued data item that cannot get its initial value once the value has been changed |
| Temporary | temp | A data item holding some value for a very short time only |
| Organizer | sortArray | A data structure storing elements that can be rearranged |
| Container | processQueue | A data structure storing elements that can be added and removed |
| Walker | currNode | A data item traversing in a data structure |
The web pages in this site represent roles as of the version 2.0. Older versions of some pages can be found here.
Last updated: November 29, 2005