> For the complete documentation index, see [llms.txt](https://docs.space.id/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.space.id/payment-id/core-contracts.md). # Core Contracts ### PID `PID` is the core NFT contract that represents Payment ID ownership as ERC-721 tokens. It handles token registration, transfers, and delegates ownership and resolver management to the PIDRegistry contract. This contract implements the tokenized representation of Payment IDs, allowing them to be transferred, approved, and managed like standard NFTs. ### PIDRegistry `PIDRegistry` is a core contract in the Payment ID system that manages the mapping between tokenIds and their respective owners and resolvers. It serves as the central registry for all Payment ID records, maintaining ownership information and resolver configurations for each tokenId. ### RegistrationController `RegistrationController` is a contract that manages the registration process for Payment ID tokens. The contract allows users to register new Payment IDs and configure their address records across different source types and chains. It enforces registration rules and ensures proper initialization of associated resolver records. ### AddrResolver AddrResolver is an abstract contract responsible for managing address records associated with Payment ID tokens, supporting both direct updates and signature-based authorization. ### PublicResolver `PublicResolver` is a contract that provides additional functionality for managing operator approvals and registration controllers for Payment ID tokens. The contract supports both direct and signature-based authorization. --- # 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://docs.space.id/payment-id/core-contracts.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.