The WebAssembly Component Model

Component Model Concepts

This section introduces the core concepts and rationale of the component model.

• A WebAssembly Component is the next evolution of core WebAssembly binaries.
  • WebAssembly components are nestable -- they may contain one or more core modules and/or sub-components composed together.
• The Component Model extends core WebAssembly by introducing higher level types and interface-driven development
  • WebAssembly Interface Types (WIT) is the IDL (Interface Definition Language) used to formally define functionality for WebAssembly modules.
  • With WIT, WebAssembly components gain the ability to conform an language-agnostic and encode that support, so any WebAssembly component binary can be interrogated and executed.
  • An Interface describes the types and functions used for a specific, focused bit of functionality.
  • A World assembles interfaces to express what features a component offers, and what features it depends on.
  • A Package is a set of WIT files containing a related set of interfaces and worlds.
• The Component Model introduces the idea of a "platform" to core WebAssembly -- enabling the structured, standardized use of "host" functionality for WebAssembly "guest"s.
  • The WebAssembly System Interface (WASI) defines in WIT a family of interfaces for common system-level functions.
  • WASI defines common execution environments such as the command line (wasi:cli) or a HTTP server (wasi:http).
• The Component Model introducs makes core WebAssembly composable -- components that provide functionality and those that use them can be composed together into one resulting component