Codetown ::: a software developer's community
Class Family Accord - Abstract
An Accord class family is a hierarchy of classes for which another class hierarchy has been designated as corresponding. Class A0 is the top of the class family, class A1 extends A0, class An extends An-1.
The partner of this class family is B0 at the top, Bn extends Bn-1. Class family A and B are have an Accord relationship if, by design intention, An corresponds to Bn. In each level, there is at least one method that overrides or defines a variant with a behavior representative of the progression of requirements.
The intention of this design concept is to maintain this correspondence when, as requirements evolve, the design calls for extending An and Bn into An+1 and Bn+1. The reason for maintaining this relationship would be that A has new or refined behaviors that only make sense with reference to the state or behaviors of B at the same level.
To realize this relationship in the Java programming language, a designer could simply document the intention. However, coding would inevitably require explicit down cast to force references to the intended levels. This white paper suggests a set of Java annotations to make the Accord relationship between class families explicit and generate the necessary dispatch code and casts. The resulting generated code would in effect provide a parametric override capability.
At a minimum an annotation @Accord designates a class as the head or subclass in a class family. Its attribute has an attribute, partner, to identify the other class family. Methods that are intended to follow the progression are annotated as @Covariant. The effect is to make the method be a covariant override. Its parameter referring to a class at the same inheritance level in the partner family is treated a covariant. A prototype precompiler is (to be) provided for research purposes.
Codetown is a social network. It's got blogs, forums, groups, personal pages and more! You might think of Codetown as a funky camper van with lots of compartments for your stuff and a great multimedia system, too! Best of all, Codetown has room for all of your friends.
Created by Michael Levin Dec 18, 2008 at 6:56pm. Last updated by Michael Levin May 4, 2018.
Check out the Codetown Jobs group.
Oracle has released version 25 of the Java programming language and virtual machine. As the first LTS release since JDK 21, the final feature set includes 18 JEPs, seven of which are finalized having evolved through the incubation and preview processes. Nine of these features are focused on performance and runtime.
By Michael RedlichDylan Fox discusses how accessibility drives innovation in extended reality. Learn how the "curb cut effect" applies to XR development, leading to advancements like AI agents, novel inputs, and multisensory experiences that improve user experience for everyone, not just those with disabilities.
By Dylan FoxKaggle, in collaboration with Google DeepMind, has introduced Kaggle Game Arena, a platform designed to evaluate artificial intelligence models by testing their performance in strategy based games.
By Daniel DominguezSecurity researchers at ARMO have uncovered a significant vulnerability in Linux runtime security tools that stems from the io_uring interface, an asynchronous I/O mechanism that can completely bypass traditional system call monitoring. The research demonstrates how attackers can exploit this blind spot to operate undetected by most existing security solutions.
By Claudio MasoloPagerDuty, the incident management platform used by thousands of organisations to alert them to problems on their systems, suffered a major outage itself on 28th August 2025. In a comprehensive outage report, the company detailed the scope of the problem, the customer impact, and how it is working to prevent a recurrence.
By Matt Saunders
© 2025 Created by Michael Levin.
Powered by
You need to be a member of Codetown to add comments!
Join Codetown