Codedomain

Codedomain is a term used in computer science to describe the set of all valid encoded representations produced by a given encoding scheme for a particular data domain. It is the output side of an encoding process and is distinct from the mathematical codomain, although the two ideas are related.

In practice, codedomain refers to the set of all values that a particular encoder may emit when given inputs from its domain. The precise contents of the codedomain depend on the encoding algorithm and any constraints such as maximum length, character set, or padding rules. Defining the codedomain helps with validation, interoperability, and error handling.

Examples: the encoded outputs of an integer-to-8-bit binary encoder have a codedomain consisting of the 256 distinct 8-bit patterns from 0x00 to 0xFF. Base64 encoding of arbitrary binary data yields strings over the Base64 alphabet, with length a multiple of four and optional padding '='. URL encoding produces strings using a restricted ASCII set, with certain characters represented by percent-encoded sequences.

Relation to other concepts: the domain is the set of possible inputs; the codedomain is the set of corresponding outputs after encoding. In some contexts the codedomain may be finite, or unbounded, depending on input possibilities and the encoding method.

See also: domain, codomain, encoding, serialization, data validation.