Generally in most of the existing libs like Schema you specify that a "person entity" is a map that has particular attributes that have particular properties an

Generally in most of the existing libs like Schema you specify that a "person entity" is a map that has particular attributes that have particular properties and a "company entity" is a map that has other attributes (some of which might overlap). In spec, you specify that a first-name attribute is a string and an email attribute matches some regex. Those are specifications about the attributes and can be used across many entity types. A person entity spec is then defined as a map that contains a set of required or optional attributes. A company entity spec is a different map with different attributes, some of which might be shared with a person (like email address). This is in many ways a shift in perspective, allowing you to start defining and reusing attribute specs to a much greater degree. The use of structural systems with mathematical properties (regular expressions for sequence structure and sets for map keys) turns out to have many useful effects in computing error sets, etc.