Function
Functions are abstract mathematical representation of relations between the domain and codomain. It can be represented as a key-value pairs, or in the lambda calculus form.
Function can be used as a generic building block to represent information in general. It can be thought of as a primitive kind of data structure. This argument can be substantiated by thinking of Lambda calculus as a generalized way of encoding functions in an explicit structured data format.
Design Principle
PKC is designed with this idea in mind, that function is a kind of data, and can be recursively referenced to perform both computation and carry computational results. By thinking about this design principle at all times, all pages in PKC will be constructed and decomposed based on a functional style.