Standard Definition
Schema.org is the vocabulary for structured data on websites, launched in 2011 by the search engine consortium of Google, Microsoft, Yahoo, and Yandex. It defines an extensive hierarchy of data types — Article, Product, Organization, Person, Event, Recipe, Course, FAQPage, DefinedTerm, and many more — each with standardized properties. Through Schema.org markup, a webpage signals to search engines and AI search systems with semantic precision what type of information it contains. Schema.org is today predominantly implemented as JSON-LD in the HTML header. Successful schema markup leads to rich snippets in search results, higher AI search system visibility, and better crawler comprehensibility.
What this means in mandate practice
Schema.org is often technically overlooked — which causes economically measurable visibility losses.
First, the right schema choice is not trivial. A blog post can be marked as Article, BlogPosting, NewsArticle, or TechArticle — each with different consequences for search engine evaluation. Calvarius works with clear heuristics: time-critical news content as NewsArticle, technical explanatory content as TechArticle, definitional glossary entries as DefinedTerm, structural overviews as BlogPosting. Generic Article markup wastes this semantic precision.
Second, AI search systems increasingly weight schema markup strongly. While Google has used schema for rich snippets for years, the impact was marginal for a long time. In the AI search era, this is changing: ChatGPT Search, Claude, and Perplexity use schema data for source classification and snippet selection. A technically clean schema implementation thus becomes a substantial AI SEO lever — not only a classical SEO question.
Third, the most common error is inconsistency between schema and visible content. Schema markup that claims different information than the visible page content is considered a spam attempt and can lead to penalties. Practice example from mandates: product schema with rating values that don't come from actual reviews. Discipline: schema describes what the page actually contains — no marketing embellishment. For extensive sites, a schema validation audit is worthwhile every 6-12 months because structured data standards continuously evolve.
End of EN file — 10 Tier-1 detail pages (Stage 3b-i).