"On Understanding Data Abstraction, Revisited" referenced

My essay On Understanding Data Abstraction, Revisited (PDF with corrected figure 8) is not likely to get many academic citations, but it is mentioned frequently on the web:

• Lambda the Ultimate
• Jonathan Aldrich's Classic Papers
• Éric Tanter's Object-Oriented Programming Languages: Application and Interpretation
• Kevlin Henney's It Is Possible to Do Object-Oriented Programming in Java
• Guy Steele on Why Object-Oriented Languages Need Tail Calls (Discussion on Lambda-the-Ultimate)
• Michael Bayne's samskivert
• Tommy McGuire's Mad science, abstract data types, and objects
• stackoverflow: How does one declare an abstract data container type in Haskell?
• stackoverflow: Data types compared to OOP objects
• Stuart Sierra on Objects Are Not Abstract Data Types
• Robert Simmons on What does focusing tell us about language design? (Discussion on Lambda-the-Ultimate)
• Yin Wang on ADTs and Objects
• Kurt Schelfthout FORTY SIX AND TWO
• stackexchange: FP and OO orthogonal?
• LShift Frank Shearar Conditional statements, the lambda calculus and early/late binding

Some new ones

• Object-Oriented Programming in ML
• On Not Understanding...
• David Albert Paper of the Week: On Understanding Data Abstraction, Revisited
• bcobb: On Understanding Data Abstraction, Revisited
• redit
• Examples from Section 3 in Standard ML by Robert J. Simmons
• Onward! Most Notable Paper Award 2019 for 2009

Emails with Bob Harper

I ran into Bob Harper at POPL in Philadelphia. We chatted briefly in the hallway. We invariably disagree on most topics when we talk, but the conversation was pleasant enough. I enjoy talking to Bob, since he has a strong world-view and is a very smart guy. When I got home, Bob wrote me a followup note. After a few emails I noticed that he had updated his draft book, Practical Foundations for Programming Languages, to include two chapters that touch on topics related to object-oriented programming. I believe that a previous version of the book only mentioned objects once, in a footnote, so I was curious to read what Bob had to say about objects. I have an special interest in this question given the strong and unsupported criticisms that Bob has made about object-oriented programming in his blog, Existential Type. Over the next few weeks we exchanged almost 50 emails about the book and object-oriented programming in general.

I previously started posting the messages, because it is an interesting story. I viewed our discussion as a continuation of the debate that we began in person at POPL. Bob never manages to support his criticisms of object-oriented programming, and in the end shows that his criticisms are based on misunderstanding of the subject. At least, that is my interpretation of our exchange. He conclusions are completely different, I am sure. I have since decided to remove the posts. Just because Bob is impolite, does not mean that I have the right to be as well. If my actions offended anyone, I apologize. I will write some separate notes on his book, based on the email discussion. He has already modified the book and removed some of the unsupported claims based on our conversation.

I am still concerned with the fundamental internal conflict and lack of understanding between different camps within programming languages. It is unhealthy and reduces our reputation within the larger community. No other sub-discipline within computer science is so fundamentally at odds with itself. I will find another way to address these issues.