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.
Atlassian recently migrated 4 million Jira databases to Amazon Aurora, intending to reduce costs and improve the reliability of its Jira Cloud platform. Due to the large number of files involved and the constraints of managed services, the team developed a custom tool to orchestrate the process, as traditional cloud migration strategies were not viable.
By Renato LosioLM Studio has released version 0.3.17, introducing support for the Model Context Protocol (MCP) — a step forward in enabling language models to access external tools and data sources. Originally developed by Anthropic, MCP defines a standardized interface for connecting LLMs to services such as GitHub, Notion, or Stripe, enabling more powerful, contextual reasoning.
By Robert KrzaczyńskiGrafana released Tempo 2.8 on June 12, 2025, introducing substantial memory optimizations and expanded functionality in its trace query language, TraceQL. This update is part of an ongoing effort to make distributed tracing more performant and accessible within observability stacks.
By Craig RisiLaunched in early preview last May, Gemma 3n is now officially available. It targets mobile-first, on-device AI applications, using new techniques designed to increase efficiency and improve performance, such as per-layer embeddings and transformer nesting.
By Sergio De SimoneIn this article, we explore how AI agents are reshaping software development and the impact they have on a developer’s workflow. We introduce a practical approach to staying in control while working with these tools by adopting key best practices from the discipline of software architecture, including defining an implementation plan, splitting tasks, and so on.
By Enrico Piccinin
© 2025 Created by Michael Levin.
Powered by
You need to be a member of Codetown to add comments!
Join Codetown