Partial differential equations are often an important component of the mathematical

description of phenomena. Guided by our study of (4.32) in Chapter 4, it is natu-

ral to ask whether or not certain classes of initial-boundary value problems could

also be subsumed under some theoretical umbrella in the spirit of (4.32), albeit in

a more elaborate sense. The quick answer is yes, provided we interpret the pieces

correctly. Our work in this chapter focuses on extending the theoretical framework

from Chapter 4 to a more general setting. Some standard references used throughout

this chapter are [78, 102, 107, 133, 155, 159, 206, 219, 221, 222, 252, 265, 300].