--- title: Conservative codomain conjecture | daily.dev description: The article discusses the concept of conservative codomain conjecture in API design and explores the implications of being liberal in what one accepts and... canonical: https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Conservative codomain conjecture | daily.dev og:description: The article discusses the concept of conservative codomain conjecture in API design and explores the implications of being liberal in what one accepts and... og:url: https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia og:image: https://api.daily.dev/og/posts/9flLLPMia.png og:image:alt: Conservative codomain conjecture og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Conservative codomain conjecture **[ploeh blog](https://daily.dev/sources/ploeh)** · 15 min read · 0 upvotes · 0 comments ## Summary The article discusses the concept of conservative codomain conjecture in API design and explores the implications of being liberal in what one accepts and conservative in what one sends. It focuses on the 'Average' method as an example and provides insights into modelling contracts, error-handling, and the choice between liberal and conservative approaches. The article concludes that it is generally better to choose the design with a conservative codomain to ensure robustness and extensibility. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Don’t just attend KubeCon \+ CloudNativeCon, Merge Forward your experience\!](https://daily.dev/posts/don-t-just-attend-kubecon-cloudnativecon-merge-forward-your-experience--l0rpp73x8) · CNCF · 1 upvotes · 0 comments - [Announcing H2 2026 KCDs](https://daily.dev/posts/announcing-h2-2026-kcds-m96goajm1) · CNCF · 1 upvotes · 0 comments - [Two months of Open Community Groups](https://daily.dev/posts/two-months-of-open-community-groups-asf52zhbs) · CNCF · 0 upvotes · 0 comments --- Tags: [#architecture](https://daily.dev/tags/architecture), [#functional-programming](https://daily.dev/tags/functional-programming) [View this post on daily.dev](https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Conservative codomain conjecture","url":"https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia"},"datePublished":"2024-05-06T06:41:12.440Z","dateModified":"2024-05-09T08:43:33.910Z","description":"The article discusses the concept of conservative codomain conjecture in API design and explores the implications of being liberal in what one accepts and...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/adaf4cd64243a3027b6651c749845e14?_a=AQAEuiZ","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/adaf4cd64243a3027b6651c749845e14?_a=AQAEuiZ","isAccessibleForFree":true,"articleSection":"ploeh blog","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"ploeh blog","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/0645fe7a0b9f40ba9ef17f7a7b49e893","url":"https://daily.dev/sources/ploeh"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/conservative-codomain-conjecture-9flllpmia","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"architecture,functional-programming","timeRequired":"PT15M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"ploeh blog","item":"https://daily.dev/sources/ploeh"},{"@type":"ListItem","position":3,"name":"Conservative codomain conjecture"}]} ```