> For the complete documentation index, see [llms.txt](https://hypercerts.gitbook.io/hypercerts-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hypercerts.gitbook.io/hypercerts-docs/lexicons/introduction-to-lexicons.md). # Introduction to Lexicons ## What is a lexicon? An ATProto lexicon is essentially a schema or template that defines what data can be stored and how it should be structured. Think of it like a form with specific fields - it tells you what information is required, what's optional, and what format each piece of data should follow. ## Lexicon Categories All lexicons follow the principle that "everything is a claim" - whether it's a hypercert, a measurement, or a piece of evidence, each represents a verifiable assertion stored on the ATProto network. This creates a composable system where claims can reference and build upon each other while maintaining clear data structures and relationships. [**General Lexicons**](broken://pages/3UwgsMpD20ErXurhzmTh) provide foundational building blocks that can be shared across multiple protocols. These include common data types, standardized location references, and other universal concepts that extend beyond hypercerts alone. [**Hypercerts Lexicons**](broken://pages/FdVczwFhTBj7n5nszh0P) contain the core claim types specific to impact tracking. These lexicons define how to structure and relate different types of impact claims - from the central activity claim (the hypercert itself) to supporting claims like measurements, evidence, and evaluations. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://hypercerts.gitbook.io/hypercerts-docs/lexicons/introduction-to-lexicons.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.