Day-to-day care and feeding of XSB including bug fixes, ports, and configuration management has been done by Kostis Sagonas, David Warren, Terrance Swift, Prasad Rao, Steve Dawson, Juliana Freire, Ernie Johnson, Baoqiu Cui, Michael Kifer, Bart Demoen and Luis F. Castro.
In Version 3.1, the core engine development of the SLG-WAM has been mainly implemented by Terrance Swift, Kostis Sagonas, Prasad Rao, Juliana Freire, Ernie Johnson, Luis Castro and Rui Marques. The breakdown, very roughly, was that Terrance Swift wrote the initial tabling engine, the SLG-WAM, and built-ins. Prasad Rao reimplemented the engine's tabling subsystem to use tries for variant-based table access and Ernie Johnson extended and refactored these routines in a number of ways, including adding call subsumption. Kostis Sagonas implemented most of tabled negation. Juliana Freire revised the table scheduling mechanism starting from Version 1.5.0 to create the batched and local scheduling that is currently used. Baoqiu Cui revised the data structures used to maintain delay lists, and added attributed variables to the engine. Finally, Luis Castro rewrote the emulator to use jump tables and wrote a heap-garbage collector for the SLG-WAM. Rui Marques was mainly responsible for making XSB multi-threaded, as well as for the concurrency control algorithms used for shared tables.
Other engine work includes the following. Memory expansion code for WAM stacks was written by Ernie Johnson and Bart Demoen. Heap garbage collection was written by Luis de Castro, Kostis Sagonis and Bart Demoen. Rui Marques improved the trailing of the SLG-WAM and rewrote much of the engine to make it compliant with 64-bit architectures. Assert and retract code was based on code written by Jiyang Xu and significantly revised by David S. Warren, who added alternative, multiple, and star indexing. Trie assert/retract code, and trie interning code was written by Prasad Rao, as was most code for reclaiming table space. The current version of findall/3 was re-written from scratch by Bart Demoen, as was XSB's throw and catch mechanism. 64-bit floats were added by Charles Rojo.
In terms of Prolog code, Kostis Sagonas was responsible for HiLog compilation and associated built-ins as well as coding or revising many standard predicates. Steve Dawson implemented Unification Factoring. The revision of XSB's I/O into ISO-compatable streams was done by Michael Kifer and Terrance Swift. The auto_table and suppl_table directives were written by Kostis Sagonas. The DCG expansion module was written by Kostis Sagonas for non-tabled code and by Baoqiu Cui, Terrance Swift and David Warren for tabled code. The handling of the multifile directive was written by Baoqiu Cui. C.R. Ramakrishnan wrote the mode analyzer for XSB. Michael Kifer implemented the storage module. The incremental table maintenance subsystem was designed and implemented by Diptikalyan Saha.
For configuration management, Michael Kifer rewrote parts of the XSB code to make XSB configurable with GNU's Autoconf, implemented XSB's package system, and integrated GPP with XSB's compiler. GPP, the source code preprocessor used by XSB, was written by Denis Auroux, who also wrote the GPP manual reproduced in Appendix A.
The starting point of XSB (in 1990) was PSB-Prolog 2.0 by Jiyang Xu. PSB-Prolog in its turn was based on SB-Prolog, primarily designed and written by Saumya Debray, David S. Warren, and Jiyang Xu. Thanks are also due to Weidong Chen for his work on Prolog clause indexing for SB-Prolog, to Richard O'Keefe, who contributed the Prolog code for the Prolog reader and the C code for the tokenizer, and to Ciao Prolog whose write_term/[2,3] we use.
... Now what did I forget this time ?