Book excerpt: This book constitutes the thoroughly refereed proceedings of the 4th International Conference on Abstract State Machines, B, TLA, VDM and Z, which took place in Toulouse, France, in June 2014. The 13 full papers presented together with 3 invited talks and 19 short papers were carefully reviewed and selected from 81 submissions. The ABZ conference series is dedicated to the cross-fertilization of six related state-based and machine-based formal methods: Abstract State Machines (ASM), Alloy, B, TLA, VDM and Z. They share a common conceptual foundation and are widely used in both academia and industry for the design and analysis of hardware and software systems. The main goal of this conference series is to contribute to the integration of these formal methods, clarifying their commonalities and differences to better understand how to combine different approaches for accomplishing the various tasks in modeling, experimental validation and mathematical verification of reliable high-quality hardware/software systems.