External services#

A capability is an object that lets a function use an external service, such as storage, networking, a clock, or a model client. A helper can receive that object as an ordinary parameter, making its dependency visible and allowing tests to supply a source implementation.

Applications can also import host accessors such as filesystem(), network(), or clock() from their standard modules. They return the services associated with the current execution; Command-line programs defines the complete accessor set and lifetime rules. Accessors do not require dependency declarations on the calling function. Importing a contract type alone does not obtain a service.

Manuscript does not enforce a per-function authority set or manifest permissions. Native host services provide their normal OS access. Explicit parameters are a composition and testing technique, rather than the only route to a service. Tooling cannot claim to enumerate all reachable authority from parameter names alone; callbacks and stored values can retain services as well.

Sharing an implementation#

A network or storage implementation can receive concurrent calls. Its mutable internal state must be synchronized. References do not extend a resource’s open lifetime; methods coordinate active calls with close.

See sharing data .