asdf:load-system

(asdf:load-system name)

Loads the named system: its :depends-on systems first (recursively), then its component files in their :depends-on/:serial order, each evaluated like load. Returns the system name as a symbol. Loading the same system twice is a no-op (like require). The system definition comes from a prior asdf:defsystem, or from NAME.asd located by searching, in order: the directory of the loading file, the directories given with --system-path, and the directories in the RONTOLISP_SOURCE_REGISTRY environment variable (both accept several directories joined with the platform path separator, like PATH). For a secondary system name such as "lib/tests" the file searched is the primary system's (lib.asd).

On the interpreter, load-system is an ordinary runtime function, so a computed name works. On the compile path (JVM/WASM), a literal, top-level (asdf:load-system NAME) is expanded at compile time: the dependency systems and component files are spliced into the program exactly like the compile-time load/require include, so the compilers see the definitions natively on every backend. A load-system nested inside another form or with a computed argument is a compile error.

;; my-lib.asd
(defsystem :my-lib
  :components ((:file "main" :depends-on ("package"))
               (:file "package")))

;; run.lisp
(asdf:load-system :my-lib)
(my-lib:greet)

package.lisp loads before main.lisp (the :depends-on constraint), then the program calls into the loaded system. See the Systems guide for the full project layout and the search-path details.