CODEWITHSUNDEEP
ooplanguage-agnosticabstraction
Manish Jain
Manish Jain

Reputation: 869

Few words in this definition of Abstraction

I'm sorry if my question doesn't meet the standards of SO, but I really had some hard time going through the last few words within this definition of ABSTRACTION from Grady Booch

“An abstraction denotes the essential characteristics of an object that distinguish it from all other kinds of objects and thus provide crisply defined conceptual boundaries, relative to the perspective of the viewer"

Please explain what does he mean by "relative to the perspective of the viewer". Any example would be really helpful.

Upvotes: 1

Views: 408

Answers (2)

Sklivvz
Sklivvz

Reputation: 31133

They simply mean that from the point of view of the person trying to understand the abstraction, it should be clear what it is, what in includes and what it doesn't.

However, how is implemented might not be that clearly different from other abstractions.

For example:

A URI is a different abstraction from a Name. It's clear to a developer and a user what either are. However, implementation-wise they both might be little more than strings.

I think that what they are trying to say is that the semantics and the behaviors define abstractions correctly, not how they are going to be implemented.

Upvotes: 3

davioooh
davioooh

Reputation: 24666

Definitions in OOP world are different and not always very clear, for example, I can bring you a definition of abstraction from Tony Hoare:

"Abstraction arises from a recognition of similarities between certain objects, situations, or processes in the real world, and the decision to concentrate upon those similarities and to ignore for the time being the differences."

Maybe this is clearer to you. However, I do not care too much about the words of these definitions.

What is important to understand about abstraction is that it has the function to expose to the user (or viewer) a set of behaviors (an interface) that completely describe and identify an entity (or object). Once you know these behaviors (methods) you can and should ignore the actual implementation of these methods. What the user should care is to provide input parameters and to receive the right results.

I think this is a more practical definition of abstraction.

Upvotes: 2

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