Question: In the mathematical study of cellular automata, Rule 90 is an elementary cellular automaton based on the exclusive or function, call it "the simplest non-trivial cellular automaton", and it is described extensively in Stephen Wolfram's book, released in what year, "A New Kind of Science", Wolfram, a British-American computer scientist, physicist, and businessman?
Context: A reversible cellular automaton is a cellular automaton in which every configuration has a unique predecessor.  That is, it is a regular grid of cells, each containing a state drawn from a finite set of states, with a rule for updating all cells simultaneously based on the states of their neighbors, such that the previous state of any cell before an update can be determined uniquely from the updated states of all the cells.  The time-reversed dynamics of a reversible cellular automaton can always be described by another cellular automaton rule, possibly on a much larger neighborhood. In mathematics and computability theory, an elementary cellular automaton is a one-dimensional cellular automaton where there are two possible states (labeled 0 and 1) and the rule to determine the state of a cell in the next generation depends only on the current state of the cell and its two immediate neighbors.  As such it is one of the simplest possible models of computation.  Nevertheless, there is an elementary cellular automaton (rule 110, defined below) which is capable of universal computation. Stephen Wolfram (born 29 August 1959) is a British-American computer scientist, physicist, and businessman.  He is known for his work in computer science, mathematics, and in theoretical physics.  He is the author of the book "A New Kind of Science."  In 2012 he was named an inaugural fellow of the American Mathematical Society. Mobile automaton (plural: mobile automata) is a class of automata similar to cellular automata but which have a single "active" cell instead of updating all cells in parallel.  In a mobile automaton, the evolution rules apply only to the active cell, and also specify how the active cell moves from one generation to the next.  All cells that are not active remain the same from one generation to the next.  Mobile automata can therefore be considered a hybrid between elementary cellular automata and Turing machines. Stochastic cellular automata or 'probabilistic cellular automata' (PCA) or 'random cellular automata' or locally interacting Markov chains are an important extension of cellular automaton.  Cellular automata are a discrete-time dynamical system of interacting entities, whose state is discrete. The Movable cellular automaton (MCA) method is a method in computational solid mechanics based on the discrete concept.  It provides advantages both of classical cellular automaton and discrete element methods.  Important advantage of the МСА method is a possibility of direct simulation of materials fracture including damage generation, crack propagation, fragmentation and mass mixing.  It is difficult to simulate these processes by means of continuum mechanics methods (For example: finite element method, finite difference method, etc.), so some new concepts like peridynamics are required.  Discrete element method is very effective to simulate granular materials, but mutual forces among movable cellular automata provides simulating solids behavior.  If size of automaton will be close to zero then MCA behavior becomes like classical continuum mechanics methods. A block cellular automaton or partitioning cellular automaton is a special kind of cellular automaton in which the lattice of cells is divided into non-overlapping blocks (with different partitions at different time steps) and the transition rule is applied to a whole block at a time rather than a single cell.  Block cellular automata are useful for simulations of physical quantities, because it is straightforward to choose transition rules that obey physical constraints such as reversibility and conservation laws. A cyclic cellular automaton is a kind of cellular automaton rule developed by David Griffeath and studied by several other cellular automaton researchers.  In this system, each cell remains unchanged until some neighboring cell has a modular value exactly one unit larger than that of the cell itself, at which point it copies its neighbor's value.  One-dimensional cyclic cellular automata can be interpreted as systems of interacting particles, while cyclic cellular automata in higher dimensions exhibit complex spiraling behavior. A cellular automaton (pl.  cellular automata, abbrev.  CA) is a discrete model studied in computability theory, mathematics, physics, complexity science, theoretical biology and microstructure modeling.  Cellular automata are also called cellular spaces, tessellation automata, homogeneous structures, cellular structures, tessellation structures, and iterative arrays. In the mathematical study of cellular automata, Rule 90 is an elementary cellular automaton based on the exclusive or function.  It consists of a one-dimensional array of cells, each of which can hold either a 0 or a 1 value.  In each time step all values are simultaneously replaced by the exclusive or of their two neighboring values.  call it "the simplest non-trivial cellular automaton", and it is described extensively in Stephen Wolfram's 2002 book "A New Kind of Science".
Answer: 2002