New informational JEP: 14: The Tip & Tail Model of Library Development

[Karsten Silz]

>> On 23 Oct 2024, at 01:15, Alex Buckley <alex.buckley at oracle.com <mailto:alex.buckley at oracle.com>> wrote:
> 
> On 10/22/2024 3:17 PM, Karsten Silz wrote:
>> And then there's this: "a new tail train that they will continue
>> [to] update even after new tip releases are made". This was in the
>> "Tip & Tail" description, so I read it as a definition: "All tail
>> trains must get updates after the next tip release". Non-LTS OpenJDK
>> tail trains don't today. So, a tail train getting updates after the
>> next tip release is a recommendation, not a requirement?
> Again, that part of the Description is high level and needs to be applicable to all libraries. The most interesting scenario for users is where a tail train makes tail releases for many years, long after the next tip release has shipped, so that's how we start describing the T&T model.
> 
> I don't want to weaken the text to accommodate the JDK's T&T implementation -- "a new tail train that they MAY continue to update even after new tip releases are made" -- because this phrasing, while technically correct, will send readers off-track.

Thank you, Alex, for taking the time to answer my questions!

Here are two observations. There's no call to action here, and there's no need for you to reply.

First, I'm a JEP newbie. I thought JEPs were like standards, full of MUST and MUSTN'T, SHALL and SHAN'T. I didn't find many of these here. Instead, I found statements that were ambiguous to me. Like this one: "library developers designate a tip release as the start of a new tail train that they will continue to update even after new tip releases are made". I read that as "tail train MUST live beyond the next tip train". But it either isn't a MUST, or it's overruled by this sentence here: "Tip & tail does not specify when or why tail trains are created, nor when or why they are discontinued." As a result, I didn't know how I would move a library to the "Tip & Tail model" just by reading the JEP.

Second, the JEP cites OpenJDK and Spring Boot as "Tip & Tail" examples. However, the differences between "Generic Tip & Tail", "OpenJDK Tip & Tail", and "Spring Boot Tip & Tail" weren't clear to me from reading the JEP. "OpenJDK Tip & Tail" and "Spring Boot Tip & Tail" also seem identical, except for a different tail train length. If folks just skim the JEP and look at OpenJDK and Spring Boot instead, they may think, "'Tip & Tail' means you have to release a new tip every six months." and turn away.  I would have found a table comparing "Generic Tip & Tail", "Spring Boot Tip & Tail", and "Tip & Tail" for a feature-driven library useful. Though not in this JEP – it's already quite long. :-)


Regards,
Karsten Silz
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