| Neuro-Prolog | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause | ⊕ Japan | |
| Neuro-Prolog II | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause | ⊕ Japan | |
| NUA-Prolog | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause | ⊕ United Kingdom | Extension to the WAM for Parallel Andorra |
| NUE-Prolog | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause | ⊕ Australia | |
| Quintec Prolog | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause | ⊕ United Kingdom | |
| R-Prolog | ⊕ 1991 | ↓ ↑ ⊕ String and List Processing | ⊕ Horn clause |