Nothing can be so amusingly arrogant
as a young man who has just discovered an old idea
and thinks it is his own.
– Sidney J. Harris
By now I think I have established the legitimacy of the Six Hats, Six Coats Framework and I am presenting it here in what I am going to consider its final form:
Every notational technique is a combination of two or more of the Six Coats. What we are working toward ultimately is a language to interrelate all Six Hats and Six Coats at once.
In this post I want to think about the terms “implicit” and “explicit” and how they relate to the Six Hats, Six Coats Framework. For the purpose of this framework implicit is defined as unchanging and invisible; explicit is defined as changing and visible.
Every entity, relationship, attribute, constraint, definition and manipulation has an implicit and explicit name. As well, every motive, locale, object, method, person and event has an implicit and explicit name. An implicit name is unique and once assigned cannot be changed. An explicit name is unique, but it can be changed. The implicit name is not visible to the user. The explicit name is visible to the user.
An entity which contains its own primary key is an implicit entity. An entity which contains a key from another entity in its primary key is an explicit entity.
A relationship that connects one entity’s primary key as part of the attributes of another entity is an implicit relationship. A relationship that connects one entity’s primary key as part of another entity’s primary key is an explicit relationship.
If the primary key is never made visible to the user and cannot be changed it is an implicit primary key. If the primary key is visible and can be changed as long as it is unique it is an explicit primary key.
Attributes that are foreign keys are implicit attributes. Attributes that are non-key are explicit attributes.
Constraints are implicit when they are data listed in a foreign entity. Constraints are explicit when they are a datatype.
Definitions are implicit when they protect explicit child tables. Definitions are explicit when they cascade manipulations.
Implicit manipulations maintain an audit trail. Explicit manipulations do not maintain an audit trail.
So, what is the purpose of implicity and explicity? Primarily it is strength and flexibility. Implicit design results in rigid, but more integral systems. Explicit design results in flexible, but less complete systems. For example, in an office you have work to rule, which is implicit, and work to allow, which is explicit. Ultimately, in dealing with implicity and explicity it is best to strike a balance. No system is fully normalized or fully exceptionalized. It is necessary to allow for both normality and exceptions as no system is fully closed or fully open.