TY - JOUR T1 - The theory of classification part 4: Object types and subtyping JO - Journal of Object Technology UR - https://eprints.whiterose.ac.uk/79278/ PY - 2002/01/01 AU - Simons AJH ED - DO - DOI: 10.5381/jot.2002.1.5.c2 VL - 1 IS - 5 SP - 27 EP - 33 Y2 - 2025/05/24 ER -