This Festschrift volume has been published in honor of Frank de Boer, on the occasion of his 60th birthday. Frank S. de Boer is a prominent member of the research community in formal methods and theoretical computer science. A brief look at his lengthy publication list reveals a broad area of interest and a versatile modus operandi with: logic and constraint programming; deductive proof systems, soundness, and completeness; semantics, compositionality, and full abstraction; process algebra and decidability; multithreading and actor-based concurrency; agent programming, ontologies, and modal logic; real-time systems, timed automata, and schedulability; enterprise architectures, choreography, and coordination; testing and runtime monitoring; and cloud computing and service-level agreements. For a while, he also liked failures, especially in semantics, and optimistically concluded with the failure of failures. In fact, Frank has an opportunistic approach to research. Rather than seeing obstacles, he finds opportunities.