What is a Schema?

A schema is a formal description of the shape of data. In a relational database, the schema describes tables, columns, and types. In an API, a schema describes request and response bodies (OpenAPI uses JSON Schema for this). On the web, schema.org provides a vocabulary for describing structured data so search engines can understand page content.

Schemas are contracts. They let producers and consumers agree on shape without passing samples back and forth. Good schema practice includes versioning (when the shape changes, the old version still parses), backward compatibility (new fields do not break old consumers), and machine validation (reject data that does not match).

SheetLink Forms uses schemas at three places. The plugin defines a JSON Schema for every form integration, describing which fields exist and their types. The SheetLinkWP backend API uses Zod (TypeScript schema library) to validate every request body. And every page on sheetlinkwp.com includes schema.org structured data (FAQPage, Article, BreadcrumbList, Organization) to help search engines render rich results.