Data and Reality – after Bill Kent
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In "Data and Reality", Bill Kent made many observations pertinent to the information and description theories to follow.
Data is created to capture a perception of reality
"We are not modeling reality, but the way information about reality is processed, by people." Kent.
Databases are models of how people idealise reality, rather than reality directly.
The meaning of a message is determined in its use
“The category of a thing (i.e. what it is) might be determined by its position, or environment, or use, rather than by its intrinsic form and composition.
In the set of plastic letters my son plays with, there is an object which might be an "N" or a "Z", depending on how he holds it. Others could be "u" or "n", "b" or "q", "p" or "d". Kent.
Creators and users may find different meanings in the same structure.
The meaning intended by the creator of a structure may be different from meaning obtained by a user of that structure.
Message senders and receivers ensure mutual understanding by using shared data types
Evolution favours social groups in which meanings are shared by signal creators and users, since that helps group members to survive and flourish.
The business systems we address are formalised social systems - in which the meanings of signals are defined independently of individual message senders and receivers.
Within such a formalised social system, message receivers expect to obtain the meanings intended by message senders.
These (intended) meanings are captured in “intensional definitions” or “types” and logical grammars for arranging the types in structures.
An entity has continuity of identity, made recognisable by assignment of an identifier
“Once a concept is represented in software, what is the effect of the passing of time on it?
At what point is it appropriate to introduce a new representative into the system, because change has transformed something into a new and different thing?
The problem is one of identifying or discovering some essential invariant characteristic of a thing, which gives it its identity.
That invariant characteristic is often hard to identify, or may not exist at all.” Kent.
Instances of a type must have continuity of identity if they are to be tracked over time.
Are “caterpillar” and “butterfly” two states of one thing? Or two things of different types?
Are “applicant” “member” and two states of one thing? Or two things of different types?
There are domain-specific types/languages rather than a universal language
“In an absolute sense, there is no singular objective reality.
But we can share a common enough view of it for most of our working purposes, so that reality does appear to be objective and stable.
But the chances of achieving such a shared view become poorer when we try to encompass broader purposes, and to involve more people.” Kent.
Many types are domain-specific, and not shareable universally.
Does the term “policy” mean the same in every division of an insurance company?
Are “supplier”, “customer” and “employee” distinct entity types? Or two roles that may be played by one “person”?
The answers depend on why and how actors need to monitor and direct what happens in their environment.
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