The Two Abstractions of System Design: Hide or Reduce

I've generally heard the two concepts discussed as abstraction vs generalization.

Abstraction hides unnecessary detail. Generalization finds/surfaces commonality among items.

> oop - What's the difference between abstraction and generalization? - Stack Overflow - https://stackoverflow.com/questions/19291776/whats-the-diffe...

Creating a procedure/method is a form of abstraction. Allowing it to accept parameters is a form of generalization (by allowing it to be used for a number of similar inputs).

Simply creating an integer data type is a very simple form of generalization. Allowing operations to work against generically against any integer.

> Modularity abstraction aspires to hide the interleavings and present operations as if they were atomic. Its goal is to make the module easy to use, but in doing so it forgoes exposing concurrency or efficiency opportunities.

> In stark contrast, the modeling abstraction is about identifying what should leak and leveraging it! It exposes the fine-grained actions and orderings, and proves that invariants hold despite the interleavings. The payoff for this work is to harvest the maximum safe concurrency from the system.

I guess I don't understand the argument here because those just sound like two different flavours of the same custard to me; the difference is just the balance of work you're doing on each side of the interface, and that decision depends on use cases specific to the project.

This feels more like it's making a point about system design? Abstraction is abstraction - you can apply it at different levels within a project, and a big part of building skills in software development is in learning to zoom in and out and nail the abstraction at each stage, but ultimately you're doing the same thing over and over. I don't personally think we need categories of it.

I think it goes to show how different notions of "compression" can be (that word gets thrown a lot nowadays because of AI). Humans like simplicity for sure, but there can be different use cases for the simplicity

my takeaway was modularity abstraction (as the author describes it) hides implementation and modeling abstraction reduces the system to the min. behavioral state required to preserve your invariants

> [ Note that his list is all about modularity abstraction: TCP (hide IP), string libraries (hide character arrays), file systems (hide spinning disks), virtual memory / flat address space (hide MMU and paging), SQL (hide query plans), NFS / SMB (hide the network), C++ string classes (hide char*). ] Modularity abstraction aspires to hide the interleavings and present operations as if they were atomic.

I wouldn't go with that. Most of the listed abstraction here is about building a new model on top of the old for new capabilities. They don't bother to hide them, merely use them for new purposes.

Like TCP using IP for interconnection, but adding transport stability on top. IP is still fairly visible, but in an axiomatic way. Same with string libraries which mostly add new operations but the nature of being a list of characters is still present.

A better example of abstraction for hiding are libraries where the public interface hide the nature of implementation (things like POSIX). This aligns more with the modeling abstraction, where you extract a minimalistic version of the system. Incomplete for implementation, but enough for interfacing.

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