{"id":3353,"date":"2026-08-27T11:31:11","date_gmt":"2026-08-27T09:31:11","guid":{"rendered":"https:\/\/www.5thfloor.be\/"},"modified":"2026-09-24T13:35:11","modified_gmt":"2026-09-24T11:35:11","slug":"reecriture-iso-fonctionnelle-ia","status":"publish","type":"post","link":"https:\/\/www.5thfloor.be\/fr\/reecriture-iso-fonctionnelle-ia\/","title":{"rendered":"R\u00e9\u00e9criture iso-fonctionnelle assist\u00e9e par l'IA"},"content":{"rendered":"<p class=\"wp-block-paragraph\"><strong>Quelles sont les applications de votre portefeuille qui pr\u00e9sentent le plus grand risque, et lesquelles peuvent attendre ?<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Une fois le diagnostic pos\u00e9, vous devez vous attaquer au premier \u00e9l\u00e9ment de la liste. La r\u00e9\u00e9criture iso-fonctionnelle assist\u00e9e par l'IA correspond \u00e0 cette \u00e9tape.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Pourquoi tant de r\u00e9\u00e9critures \u00e9chouent<\/strong>?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>La r\u00e9\u00e9criture iso-fonctionnelle <\/strong>permet de reconstruire l'application avec un comportement observable identique (m\u00eames \u00e9crans, m\u00eames calculs, m\u00eames r\u00e8gles, y compris les cas limites) tout en repensant enti\u00e8rement sa structure interne. La modernisation intervient ensuite, sur des bases qui la rendent v\u00e9ritablement possible, car la ma\u00eetrise technique du sujet est d\u00e9sormais acquise.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Le r\u00f4le de l'IA, et pourquoi vos \u00e9quipes restent au centre ?<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Figer un comportement suppose de savoir ce que le syst\u00e8me fait aujourd'hui, et cette information n'existe nulle part sous forme \u00e9crite. <strong>Un syst\u00e8me ancien porte une connaissance absente de sa documentation :<\/strong>des r\u00e8gles jamais consign\u00e9es, des cas particuliers ajout\u00e9s au fil des r\u00e9formes, des contournements pos\u00e9s pour r\u00e9pondre \u00e0 un besoin r\u00e9el du terrain.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>L'IA intervient pr\u00e9cis\u00e9ment \u00e0 ce moment-l\u00e0<\/strong>. Elle lit l'ancien plut\u00f4t qu'elle ne con\u00e7oit le nouveau. <strong>Elle parcourt le code source, en extrait les r\u00e8gles r\u00e9ellement appliqu\u00e9es et les restitue sous une forme que vos analystes peuvent lire, interroger et corriger<\/strong>. C'est le travail que notre solution effectue d\u00e9j\u00e0 sur l'ensemble de votre base de code, et qui est ici appliqu\u00e9 \u00e0 l'application que vous \u00eates en train de r\u00e9\u00e9crire. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong><a href=\"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/09\/5thfloor_white_paper_AI_swarm_iso_functional_rewrite_EN.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">T\u00e9l\u00e9charger le white paper<\/a><\/strong><\/p>\n\n\n\n<div class=\"wp-block-uagb-image uagb-block-1ecbc856 wp-block-uagb-image--layout-default wp-block-uagb-image--effect-static wp-block-uagb-image--align-none\"><figure class=\"wp-block-uagb-image__figure\"><a class href=\"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/09\/5thfloor_white_paper_AI_swarm_iso_functional_rewrite_EN.pdf\" target=\"_blank\" rel=\"noreferrer noopener\"><noscript><img decoding=\"async\" src=\"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/5th-floor-whitepaper-isofunctionnal-rewrite-1024x909.png\" alt class=\"uag-image-3357\" width=\"1118\" height=\"992\" title=\"5th-floor-whitepaper-isofunctionnal-rewrite\" loading=\"lazy\" role=\"img\"><\/noscript><img decoding=\"async\" src=\"data:image\/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%201118%20992%22%3E%3C%2Fsvg%3E\" alt class=\"uag-image-3357 lazyload\" width=\"1118\" height=\"992\" title=\"5th-floor-whitepaper-isofunctionnal-rewrite\" loading=\"lazy\" role=\"img\" data-src=\"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/5th-floor-whitepaper-isofunctionnal-rewrite-1024x909.png\"><\/a><\/figure><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<div class=\"wp-block-uagb-advanced-heading uagb-block-3da65d22\"><h2 class=\"uagb-heading-text\">FAQ<\/h2><\/div>\n\n\n<div class=\"wp-block-uagb-faq uagb-faq__outer-wrap uagb-block-9853f0c4 uagb-faq-icon-row uagb-faq-layout-accordion uagb-faq-expand-first-true uagb-faq-inactive-other-true uagb-faq__wrap uagb-buttons-layout-wrap uagb-faq-equal-height\" data-faqtoggle=\"true\" role=\"tablist\"><div class=\"wp-block-uagb-faq-child uagb-faq-child__outer-wrap uagb-faq-item uagb-block-2a95f4d8\" role=\"tab\" tabindex=\"0\"><div class=\"uagb-faq-questions-button uagb-faq-questions\">\t\t\t<span class=\"uagb-icon uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M432 256c0 17.69-14.33 32.01-32 32.01H256v144c0 17.69-14.33 31.99-32 31.99s-32-14.3-32-31.99v-144H48c-17.67 0-32-14.32-32-32.01s14.33-31.99 32-31.99H192v-144c0-17.69 14.33-32.01 32-32.01s32 14.32 32 32.01v144h144C417.7 224 432 238.3 432 256z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t<span class=\"uagb-icon-active uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M400 288h-352c-17.69 0-32-14.32-32-32.01s14.31-31.99 32-31.99h352c17.69 0 32 14.3 32 31.99S417.7 288 400 288z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t<span class=\"uagb-question\">En quoi cela diff\u00e8re d'une conversion automatis\u00e9e de code ?<\/span><\/div><div class=\"uagb-faq-content\"><p>Une conversion traduit un langage vers un autre en conservant la structure d'origine. Le r\u00e9sultat est nouveau et reste difficile \u00e0 maintenir. Une r\u00e9\u00e9criture conserve le comportement et reconstruit la structure, ce qui suppose des d\u00e9cisions d'architecture prises avec vous.<\/p><\/div><\/div><div class=\"wp-block-uagb-faq-child uagb-faq-child__outer-wrap uagb-faq-item uagb-block-83363705\" role=\"tab\" tabindex=\"0\"><div class=\"uagb-faq-questions-button uagb-faq-questions\">\t\t\t<span class=\"uagb-icon uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M432 256c0 17.69-14.33 32.01-32 32.01H256v144c0 17.69-14.33 31.99-32 31.99s-32-14.3-32-31.99v-144H48c-17.67 0-32-14.32-32-32.01s14.33-31.99 32-31.99H192v-144c0-17.69 14.33-32.01 32-32.01s32 14.32 32 32.01v144h144C417.7 224 432 238.3 432 256z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t<span class=\"uagb-icon-active uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M400 288h-352c-17.69 0-32-14.32-32-32.01s14.31-31.99 32-31.99h352c17.69 0 32 14.3 32 31.99S417.7 288 400 288z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t<span class=\"uagb-question\">Quelle diff\u00e9rence avec une migration ou une refonte ?<\/span><\/div><div class=\"uagb-faq-content\"><p>Une migration change l'infrastructure sans toucher au code m\u00e9tier. Une r\u00e9\u00e9criture iso-fonctionnelle change la technologie en conservant le comportement. Une refonte change le comportement, donc le processus m\u00e9tier et le cadre r\u00e9glementaire qui va avec.<\/p><\/div><\/div><div class=\"wp-block-uagb-faq-child uagb-faq-child__outer-wrap uagb-faq-item uagb-block-83363705\" role=\"tab\" tabindex=\"0\"><div class=\"uagb-faq-questions-button uagb-faq-questions\">\t\t\t<span class=\"uagb-icon uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M432 256c0 17.69-14.33 32.01-32 32.01H256v144c0 17.69-14.33 31.99-32 31.99s-32-14.3-32-31.99v-144H48c-17.67 0-32-14.32-32-32.01s14.33-31.99 32-31.99H192v-144c0-17.69 14.33-32.01 32-32.01s32 14.32 32 32.01v144h144C417.7 224 432 238.3 432 256z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t<span class=\"uagb-icon-active uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M400 288h-352c-17.69 0-32-14.32-32-32.01s14.31-31.99 32-31.99h352c17.69 0 32 14.3 32 31.99S417.7 288 400 288z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t<span class=\"uagb-question\">L'IA \u00e9crit-elle le code toute seule ?<\/span><\/div><div class=\"uagb-faq-content\"><p>Non. Elle produit un premier jet, sur la lecture de l'existant comme sur la g\u00e9n\u00e9ration. Vos \u00e9quipes valident le comportement obtenu contre le comportement attendu. Nous documentons ce m\u00e9canisme en d\u00e9tail dans notre rapport d'exp\u00e9rimentation.<\/p><\/div><\/div><div class=\"wp-block-uagb-faq-child uagb-faq-child__outer-wrap uagb-faq-item uagb-block-83363705\" role=\"tab\" tabindex=\"0\"><div class=\"uagb-faq-questions-button uagb-faq-questions\">\t\t\t<span class=\"uagb-icon uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M432 256c0 17.69-14.33 32.01-32 32.01H256v144c0 17.69-14.33 31.99-32 31.99s-32-14.3-32-31.99v-144H48c-17.67 0-32-14.32-32-32.01s14.33-31.99 32-31.99H192v-144c0-17.69 14.33-32.01 32-32.01s32 14.32 32 32.01v144h144C417.7 224 432 238.3 432 256z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t<span class=\"uagb-icon-active uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M400 288h-352c-17.69 0-32-14.32-32-32.01s14.31-31.99 32-31.99h352c17.69 0 32 14.3 32 31.99S417.7 288 400 288z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t<span class=\"uagb-question\">Qui poss\u00e8de le code produit ?<\/span><\/div><div class=\"uagb-faq-content\"><p>Vous. Ce point se verrouille contractuellement d\u00e8s la premi\u00e8re offre, avec la question de la localisation des sources pendant les travaux.<\/p><\/div><\/div><div class=\"wp-block-uagb-faq-child uagb-faq-child__outer-wrap uagb-faq-item uagb-block-83363705\" role=\"tab\" tabindex=\"0\"><div class=\"uagb-faq-questions-button uagb-faq-questions\">\t\t\t<span class=\"uagb-icon uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M432 256c0 17.69-14.33 32.01-32 32.01H256v144c0 17.69-14.33 31.99-32 31.99s-32-14.3-32-31.99v-144H48c-17.67 0-32-14.32-32-32.01s14.33-31.99 32-31.99H192v-144c0-17.69 14.33-32.01 32-32.01s32 14.32 32 32.01v144h144C417.7 224 432 238.3 432 256z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t<span class=\"uagb-icon-active uagb-faq-icon-wrap\">\n\t\t\t\t\t\t\t\t<svg viewbox=\"0 0 448 512\"><path d=\"M400 288h-352c-17.69 0-32-14.32-32-32.01s14.31-31.99 32-31.99h352c17.69 0 32 14.3 32 31.99S417.7 288 400 288z\" \/><\/svg>\n\t\t\t\t\t\t\t<\/span>\n\t\t\t<span class=\"uagb-question\">Cela ne concerne-t-il que le COBOL ?<\/span><\/div><div class=\"uagb-faq-content\"><p>Non. La difficult\u00e9 vient de l'absence de sp\u00e9cification et du couplage, pas du langage. Une application de dix ans mal document\u00e9e pose le m\u00eame probl\u00e8me.<\/p><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>Which applications in your portfolio pose the greatest risk, and which ones can wait? Once the diagnosis is made, you need to take action on the one at the top of the list. AI-assisted iso-functional rewriting is this step. Why do so many rewrites fail? Iso-functional rewriting rebuilds the application with identical observable behavior (same [&hellip;]<\/p>\n","protected":false},"author":9,"featured_media":3356,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"_uag_custom_page_level_css":"","_post_is_featured":"","_post_subtitle":"","_post_team_members":[],"_post_wp_authors":[9],"_post_external_authors":[],"footnotes":""},"categories":[49],"tags":[],"class_list":["post-3353","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>AI-Assisted Iso-Functional Rewriting of Legacy Systems<\/title>\n<meta name=\"description\" content=\"Iso-functional rewriting rebuilds a critical legacy application with identical behavior. AI reads the existing code, your teams validate every rule.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.5thfloor.be\/fr\/reecriture-iso-fonctionnelle-ia\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"AI-Assisted Iso-Functional Rewriting of Legacy Systems\" \/>\n<meta property=\"og:description\" content=\"Iso-functional rewriting rebuilds a critical legacy application with identical behavior. AI reads the existing code, your teams validate every rule.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.5thfloor.be\/fr\/reecriture-iso-fonctionnelle-ia\/\" \/>\n<meta property=\"og:site_name\" content=\"5th floor\" \/>\n<meta property=\"article:published_time\" content=\"2026-08-27T09:31:11+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-09-24T11:35:11+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1280\" \/>\n\t<meta property=\"og:image:height\" content=\"1920\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Gilles Stragier\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"Gilles Stragier\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/\"},\"author\":{\"name\":\"Gilles Stragier\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#\\\/schema\\\/person\\\/d86d41955340da69d18bfa0487edc373\"},\"headline\":\"AI-Assisted Iso-functional Rewriting\",\"datePublished\":\"2026-08-27T09:31:11+00:00\",\"dateModified\":\"2026-09-24T11:35:11+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/\"},\"wordCount\":223,\"publisher\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/08\\\/iso-functional-rewrite-application-it.jpg\",\"articleSection\":[\"Projects\"],\"inLanguage\":\"fr-FR\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/\",\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/\",\"name\":\"AI-Assisted Iso-Functional Rewriting of Legacy Systems\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/08\\\/iso-functional-rewrite-application-it.jpg\",\"datePublished\":\"2026-08-27T09:31:11+00:00\",\"dateModified\":\"2026-09-24T11:35:11+00:00\",\"description\":\"Iso-functional rewriting rebuilds a critical legacy application with identical behavior. AI reads the existing code, your teams validate every rule.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#breadcrumb\"},\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/08\\\/iso-functional-rewrite-application-it.jpg\",\"contentUrl\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/08\\\/iso-functional-rewrite-application-it.jpg\",\"width\":1280,\"height\":1920,\"caption\":\"iso functional rewrite code\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/ai-legacy-application-rewrite\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.5thfloor.be\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"AI-Assisted Iso-functional Rewriting\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#website\",\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/\",\"name\":\"5th floor \u2014 Digital transformation partner for the Belgian public sector\",\"description\":\"Digital transformation partner for Belgian public sector institutions since 2017. Specialised in legacy modernisation through software upcycling, responsible AI integration, and organisational change management. B Corporation Certified since 2025. Around 120 consultants serving ONE, SPW, ONEM, and other major Belgian public institutions.\",\"publisher\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.5thfloor.be\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"fr-FR\"},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#organization\",\"name\":\"5th floor\",\"alternateName\":\"5th floor software\",\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#\\\/schema\\\/logo\\\/image\\\/\",\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/5th_floor_software_logo.jpeg\",\"contentUrl\":\"https:\\\/\\\/www.5thfloor.be\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/5th_floor_software_logo.jpeg\",\"width\":200,\"height\":200,\"caption\":\"5th floor\"},\"image\":{\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#\\\/schema\\\/logo\\\/image\\\/\"},\"sameAs\":[\"https:\\\/\\\/www.linkedin.com\\\/company\\\/5th-floor-software\\\/\"]},{\"@type\":\"Person\",\"@id\":\"https:\\\/\\\/www.5thfloor.be\\\/#\\\/schema\\\/person\\\/d86d41955340da69d18bfa0487edc373\",\"name\":\"Gilles Stragier\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g\",\"url\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g\",\"contentUrl\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g\",\"caption\":\"Gilles Stragier\"},\"sameAs\":[\"https:\\\/\\\/www.linkedin.com\\\/in\\\/gilles-stragier-6172912\\\/\"],\"url\":\"https:\\\/\\\/www.5thfloor.be\\\/fr\\\/author\\\/gilles-stragier5thfloor-be\\\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"R\u00e9\u00e9criture legacy assist\u00e9e par IA, m\u00eame comportement","description":"La r\u00e9\u00e9criture iso-fonctionnelle reconstruit une application legacy \u00e0 comportement identique. L'IA lit le code, vos \u00e9quipes valident chaque r\u00e8gle.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.5thfloor.be\/fr\/reecriture-iso-fonctionnelle-ia\/","og_locale":"fr_FR","og_type":"article","og_title":"AI-Assisted Iso-Functional Rewriting of Legacy Systems","og_description":"Iso-functional rewriting rebuilds a critical legacy application with identical behavior. AI reads the existing code, your teams validate every rule.","og_url":"https:\/\/www.5thfloor.be\/fr\/reecriture-iso-fonctionnelle-ia\/","og_site_name":"5th floor","article_published_time":"2026-08-27T09:31:11+00:00","article_modified_time":"2026-09-24T11:35:11+00:00","og_image":[{"width":1280,"height":1920,"url":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg","type":"image\/jpeg"}],"author":"Gilles Stragier","twitter_card":"summary_large_image","twitter_misc":{"\u00c9crit par":"Gilles Stragier","Dur\u00e9e de lecture estim\u00e9e":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#article","isPartOf":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/"},"author":{"name":"Gilles Stragier","@id":"https:\/\/www.5thfloor.be\/#\/schema\/person\/d86d41955340da69d18bfa0487edc373"},"headline":"AI-Assisted Iso-functional Rewriting","datePublished":"2026-08-27T09:31:11+00:00","dateModified":"2026-09-24T11:35:11+00:00","mainEntityOfPage":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/"},"wordCount":223,"publisher":{"@id":"https:\/\/www.5thfloor.be\/#organization"},"image":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#primaryimage"},"thumbnailUrl":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg","articleSection":["Projects"],"inLanguage":"fr-FR"},{"@type":"WebPage","@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/","url":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/","name":"R\u00e9\u00e9criture legacy assist\u00e9e par IA, m\u00eame comportement","isPartOf":{"@id":"https:\/\/www.5thfloor.be\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#primaryimage"},"image":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#primaryimage"},"thumbnailUrl":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg","datePublished":"2026-08-27T09:31:11+00:00","dateModified":"2026-09-24T11:35:11+00:00","description":"La r\u00e9\u00e9criture iso-fonctionnelle reconstruit une application legacy \u00e0 comportement identique. L'IA lit le code, vos \u00e9quipes valident chaque r\u00e8gle.","breadcrumb":{"@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#breadcrumb"},"inLanguage":"fr-FR","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/"]}]},{"@type":"ImageObject","inLanguage":"fr-FR","@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#primaryimage","url":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg","contentUrl":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg","width":1280,"height":1920,"caption":"iso functional rewrite code"},{"@type":"BreadcrumbList","@id":"https:\/\/www.5thfloor.be\/ai-legacy-application-rewrite\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.5thfloor.be\/"},{"@type":"ListItem","position":2,"name":"AI-Assisted Iso-functional Rewriting"}]},{"@type":"WebSite","@id":"https:\/\/www.5thfloor.be\/#website","url":"https:\/\/www.5thfloor.be\/","name":"5th floor \u2014 Partenaire de transformation num\u00e9rique pour le secteur public belge","description":"Partenaire de transformation num\u00e9rique pour les institutions du secteur public belge depuis 2017. Sp\u00e9cialis\u00e9 dans la modernisation des syst\u00e8mes existants par le recyclage de logiciels, l'int\u00e9gration d'IA responsable et la gestion du changement organisationnel. Certifi\u00e9 B Corporation depuis 2025. Environ 120 consultants au service de ONE, SPW, ONEM, et d'autres grandes institutions publiques belges.","publisher":{"@id":"https:\/\/www.5thfloor.be\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.5thfloor.be\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"fr-FR"},{"@type":"Organization","@id":"https:\/\/www.5thfloor.be\/#organization","name":"5th floor","alternateName":"5th floor software","url":"https:\/\/www.5thfloor.be\/","logo":{"@type":"ImageObject","inLanguage":"fr-FR","@id":"https:\/\/www.5thfloor.be\/#\/schema\/logo\/image\/","url":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/04\/5th_floor_software_logo.jpeg","contentUrl":"https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/04\/5th_floor_software_logo.jpeg","width":200,"height":200,"caption":"5th floor"},"image":{"@id":"https:\/\/www.5thfloor.be\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.linkedin.com\/company\/5th-floor-software\/"]},{"@type":"Person","@id":"https:\/\/www.5thfloor.be\/#\/schema\/person\/d86d41955340da69d18bfa0487edc373","name":"Gilles Stragier","image":{"@type":"ImageObject","inLanguage":"fr-FR","@id":"https:\/\/secure.gravatar.com\/avatar\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/1ba61e1de10ca59808e3ad465607531c5d1735c7dc692f2bfecf8fc08889a50d?s=96&d=mm&r=g","caption":"Gilles Stragier"},"sameAs":["https:\/\/www.linkedin.com\/in\/gilles-stragier-6172912\/"],"url":"https:\/\/www.5thfloor.be\/fr\/author\/gilles-stragier5thfloor-be\/"}]}},"uagb_featured_image_src":{"full":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg",1280,1920,false],"thumbnail":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-150x150.jpg",150,150,true],"medium":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-200x300.jpg",200,300,true],"medium_large":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-768x1152.jpg",768,1152,true],"large":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-683x1024.jpg",683,1024,true],"1536x1536":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-1024x1536.jpg",1024,1536,true],"2048x2048":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it.jpg",1280,1920,false],"trp-custom-language-flag":["https:\/\/www.5thfloor.be\/wp-content\/uploads\/2026\/08\/iso-functional-rewrite-application-it-8x12.jpg",8,12,true]},"uagb_author_info":{"display_name":"Gilles Stragier","author_link":"https:\/\/www.5thfloor.be\/fr\/author\/gilles-stragier5thfloor-be\/"},"uagb_comment_info":0,"uagb_excerpt":"Which applications in your portfolio pose the greatest risk, and which ones can wait? Once the diagnosis is made, you need to take action on the one at the top of the list. AI-assisted iso-functional rewriting is this step. Why do so many rewrites fail? Iso-functional rewriting rebuilds the application with identical observable behavior (same\u2026","_links":{"self":[{"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/posts\/3353","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/comments?post=3353"}],"version-history":[{"count":11,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/posts\/3353\/revisions"}],"predecessor-version":[{"id":3478,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/posts\/3353\/revisions\/3478"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/media\/3356"}],"wp:attachment":[{"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/media?parent=3353"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/categories?post=3353"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.5thfloor.be\/fr\/wp-json\/wp\/v2\/tags?post=3353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}