Logtalk is an object-oriented logic programming language that can use most Prolog implementations as a back-end compiler. As a multi-paradigm language, it includes support for both prototypes and classes, protocols (interfaces), component-based programming through category-based composition, event-driven programming, and high-level multi-threading programming.
TCLP is a type checker for Prolog dialects. It is written in SICStus Prolog. Its goal is to statically trap programming errors like illegal arguments used in a call for a predicate or illegally built data structures with respect to a given typing for function symbols or predicates. TCLP is also capable of type inference for user predicates. Supported dialects include ISO-Prolog, GNU-Prolog, and SICStus Prolog.
Ciao is a complete Prolog system subsuming ISO-Prolog with a novel modular design which allows both restricting and extending the language. Ciao extensions currently include feature terms (records), higher-order, functions, constraints, objects, persistent predicates, a good base for distributed execution (agents), and concurrency. Libraries also support WWW programming, sockets, and external interfaces (C, Java, TCL/Tk, relational databases, etc.). An Emacs-based environment, a stand-alone compiler, and a toplevel shell are also provided.