Requirements

This section contains the requirements for the WRT project.

Functional Requirements

Requirement: Resumable Interpreter REQ_001

status: implemented links incoming: SPEC_001, SPEC_006, SPEC_002, IMPL_001, REQ_005

The interpreter shall be resumable, allowing operation with fuel or other implementations of bounded run-time that require the interpreter to be halted and later resumed as if it was not halted.

Requirement: Baremetal Support REQ_002

status: planned links incoming: REQ_006

The interpreter shall be executable on bare-metal environments with no reliance on any specific functionality from the provided execution environment, as it shall be ready for embedding to any environment that Rust can compile for.

Requirement: Bounded Execution REQ_003

status: implemented links incoming: SPEC_001, SPEC_006, SPEC_002, IMPL_001, SPEC_005, IMPL_008, REQ_007

The interpreter shall yield back control flow eventually, allowing users to call the interpreter with a bound and expect a result in a finite amount of time or bytecode operations, even if the bytecode itself never finishes execution.

Requirement: State Migration REQ_004

status: planned links incoming: REQ_008

The interpreter state shall be able to halt on one computer and continue execution on another, enabling various workflows in deployments of multiple computers for load-balancing or redundancy purposes.

Requirement: WebAssembly Component Model Support REQ_014

status: planned links incoming: SPEC_001, SPEC_003, IMPL_005, IMPL_006, REQ_021, REQ_018, REQ_019, REQ_020

The interpreter shall implement the WebAssembly Component Model Preview 2 specification, including: - Component model validation - Resource type handling - Interface types - Component instantiation and linking - Resource lifetime management - Custom section handling - Component model binary format parsing

Requirement: Component Model Binary Format REQ_021

status: partial links outgoing: REQ_014

The interpreter shall strictly implement the WebAssembly Component Model binary format as specified in the official WebAssembly Component Model specification at WebAssembly/component-model, including: Magic bytes (0x00, 0x61, 0x73, 0x6D) followed by version (0x0D, 0x00, 0x01, 0x00) Component sections with proper section IDs Type section encoding with canonical type representation Import section handling with component, instance, and function imports Core module sections including validation and embedding Component instances section with proper instance creation Export section with named exports and index references Component custom sections for metadata and tooling Canonical ABI encoding/decoding for interface values LEB128 encoding for integers and field counts

Requirement: WASI Logging Support REQ_015

status: partial links incoming: SPEC_004, IMPL_007, SPEC_005, IMPL_008, REQ_016

The interpreter shall implement the WASI logging API as specified in the wasi-logging proposal, providing: - Support for all defined log levels (Error, Warn, Info, Debug, Trace) - Context-based logging - Stderr integration - Thread-safe logging operations

Requirement: Platform-Specific Logging REQ_016

status: planned links outgoing: REQ_015 links incoming: SPEC_004

The WASI logging implementation shall provide platform-specific backends: - Linux: syslog integration with proper facility and priority mapping - macOS: Unified Logging System (os_log) integration - Generic fallback implementation for other platforms

Low-Level Functional Requirements

Requirement: Stackless Implementation REQ_005

status: implemented links outgoing: REQ_001 links incoming: SPEC_002, IMPL_004

The interpreter shall be stackless, storing the stack of the interpreted bytecode in a traditional data structure rather than using function calls in the host environment.

Requirement: No Standard Library REQ_006

status: implemented links outgoing: REQ_002 links incoming: SPEC_002

The interpreter shall be implemented in no_std Rust, only relying on functionality provided by no_std to enable execution on bare environments where no operating system is available.

Requirement: Fuel Mechanism REQ_007

status: implemented links outgoing: REQ_003 links incoming: SPEC_006, SPEC_002, IMPL_001

The interpreter shall support fuel bounded execution, where each bytecode instruction is associated with a specific amount of fuel consumed during execution.

Requirement: State Serialization REQ_008

status: planned links outgoing: REQ_004

The interpreter state shall be de-/serializable to enable migration to other computers and support check-point/lock-step execution.

Requirement: WebAssembly Core Implementation REQ_018

status: partial links outgoing: REQ_014 links incoming: SPEC_001, IMPL_002, IMPL_003

The interpreter shall implement the WebAssembly Core specification, including: - Value types and reference types - Instructions and control flow - Function calls and tables - Memory and data segments - Global variables - Exception handling - SIMD operations - Threading support

Requirement: Component Model Implementation REQ_019

status: partial links outgoing: REQ_014 links incoming: SPEC_003, IMPL_005, IMPL_006

The interpreter shall implement the Component Model specification, including: - WIT format parsing and validation - Component model binary format parsing - Resource type implementation - Interface type handling - Component instantiation - Component linking - Resource lifetime management

Dependency Requirements

Requirement: Logging Support REQ_009

status: implemented

The interpreter shall have an optional dependency on the log crate version 0.4.22 for observability and debugging purposes.

Requirement: Math Library REQ_010

status: planned

The interpreter may depend on the libm crate version 0.2.8 for floating-point operations required in no_std environments.

Requirement: Rust Version REQ_011

status: implemented

The interpreter shall compile on Rust 1.76.0 and later versions.

Requirement: Component Model Tools REQ_020

status: partial links outgoing: REQ_014 links incoming: SPEC_003

The interpreter shall use the following tools for Component Model development: - wit-parser >= 0.12.0 for WIT file parsing and validation - wit-bindgen >= 0.12.0 for interface generation - wit-component >= 0.12.0 for component model binary format handling

Observability Requirements

Requirement: Instrumentation Support REQ_012

status: partial links incoming: REQ_013

The interpreter shall implement means for instrumentation to support certification evidence generation, debugging, and run-time monitoring.

Requirement: Coverage Measurement REQ_013

status: partial links outgoing: REQ_012

The instrumentation shall enable the measurement of: Statement coverage (DO-178C DAL-C) Decision coverage (DO-178C DAL-B) Modified condition/decision coverage (DO-178C DAL-A)

Implementation Status

ID	Title	Status
REQ_001	Resumable Interpreter	implemented
REQ_002	Baremetal Support	planned
REQ_003	Bounded Execution	implemented
REQ_004	State Migration	planned
REQ_005	Stackless Implementation	implemented
REQ_006	No Standard Library	implemented
REQ_007	Fuel Mechanism	implemented
REQ_008	State Serialization	planned
REQ_009	Logging Support	implemented
REQ_010	Math Library	planned
REQ_011	Rust Version	implemented
REQ_012	Instrumentation Support	partial
REQ_013	Coverage Measurement	partial
REQ_014	WebAssembly Component Model Support	planned
REQ_015	WASI Logging Support	partial
REQ_016	Platform-Specific Logging	planned
REQ_018	WebAssembly Core Implementation	partial
REQ_019	Component Model Implementation	partial
REQ_020	Component Model Tools	partial
REQ_021	Component Model Binary Format	partial

Requirement Relationships