Categories represent abstractions of other mathematical concepts. Conceptual skills are used in planning and dealing with ideas and abstractions. PSDL addresses these issues by introducing control abstractions that include declarative timing constraints. These architectures are made of specific choices of abstractions. Walter Burkert describes them as "persons, not abstractions, ideas or concepts". Many abstractions, including eternal objects, are potential ingredients of processes. Robust data models often identify abstractions of such entities. Phonology is concerned with the linguistic abstractions and categorizations of sounds. CLU supports type parameterized user-defined data abstractions. Other lambda abstractions are incorrect in mathematics. Such a dynamic flow is made possible by object interactions that are defined through abstractions. They provide rich and powerful abstractions of the underlying hardware. Oberon supports extension of record types for the construction of abstractions and heterogeneous structures. Despite the constraints imposed by Java's abstractions, the JVM does not preclude the possibility. This area has to do with logic, abstractions, reasoning, numbers and critical thinking.