Jonathan Jacky is a Research Scientist at University of Washington. Colleagues describe him as "Of course, I (sort of) knew Jon already before we finally met. I found his book "The Way of Z", just because of his emphasis on the pragmatics of formal specification, extremely inspiring and refreshing when teaching it in software-engineering classes. When we finally met in a tutorial on testing, I was surprised about the wide range of interests he covered in the field, his openness to new approaches and the sincerity in which he discussed pros and cons. I will never forgive him, though, that he did not cite our papers ;-)" and "Jonathan Jacky has been an exemplary user of the Z notation to formally specify and develop the software in an important computer-based medical safety-critical application. He has also written one of the best Z textbooks available, and certainly the most practical one. I recommend him as a software developer, especially for high integrity systems."