The Weaver specifications (RFCs) capture abstractions, models, protocols and data formats for enabling cross-ledger communication.
For newcomers we recommend starting with the protocol overview document followed by the RFCs on models. Protocol engineers will find in RFC: 01-007 a useful overview of the relay model, and may then progress on to reading one of the existing protocols' design and implementation; e.g., the data transfer protocol in RFC: 02-002. If you are interested in adding support for a new ledger technology, see implementing a new driver and implementing interoperability modules for your ledger technology. Where relevant we use ABNF for formal syntax definitions.