Languages are living organisms. The lifeblood provided by experienced users is key to their growth and their improvement. We have benefited much from colleagues who have used different alpha versions of Maude; we cannot mention them all, but Christiano Braga, Feng Chen, Grit Denker, Azadeh Farzan, Joe Hendrix, Merrill Knapp, Nirman Kumar, Miguel Palomino, Peter Ölveczky, Adrián Riesco, Dilia Rodriguez, Grigore Rosu, Ralf Sasse, Koushik Sen, Ambarish Sridharanarayanan, Mark-Oliver Stehr, Prasanna Thati, and Alberto Verdejo deserve special thanks for their creative uses of Maude and their suggestions for improving the language. Thanks to Christiano Braga, Peter Mosses, Peter Ölveczky, Miguel Palomino, Sylvan Pinsky, Isabel Pita, Adrián Riesco, Dilia Rodriguez, Manuel Roldán, Mark-Oliver Stehr, Antonio Vallecillo, and Alberto Verdejo for their comments on previous versions of this document.
We are grateful to José Quesada, who developed MSCP, the Maude parser. MSCP is implemented using SCP [67] as the formal kernel, and provides a basis for flexible syntax definition, and an efficient treatment of what might be called syntactic reflection.
As already mentioned, Maude's historical precursor is the OBJ3 language [44]. The OBJ3 experience has greatly influenced the Maude design and philosophy, and we are grateful to all our former OBJ colleagues for this. Joseph Goguen should be mentioned in particular, because of his enormous influence in all aspects of OBJ; and Tim Winkler for having implemented a state-of-the-art OBJ3 system with such great skill.
Two other rewriting logic languages, ELAN [6] and CafeOBJ [41], have provided a rich stimulus to the design of Maude. Although our language design solutions have often been different, we have all been wrestling with a similar problem: how to best obtain efficient language implementations of rewriting-based languages. We have benefited much from the ELAN and CafeOBJ experience, and from many discussions with their main designers and implementers: Claude and Hélène Kirchner, Marian Vittek, Pierre-Etienne Moreau, Kokichi Futatsugi, Râzvan Diaconescu, Ataru Nakagawa, Toshimi Sawada, and Makoto Ishisone.
Bringing a new language design to maturity requires a long-term research effort and substantial resources. We are not there yet, but much has been advanced since the early design phases. Perhaps the longest, most sustained support has come from the US Office for Naval Research (ONR) through a series of contracts. We are most grateful to Dr. Ralph Wachter at ONR for his continued encouragement at every step of the way. The US Defense Advance Research Projects Agency (DARPA), the US National Science Foundation (NSF), and the Spanish Ministry for Education and Science (MEC) have also contributed important resources to the development of Maude, its foundations, and its applications.