The DL/I parser conforms to the language as defined by IBM. The parser does build a syntax tree. The parser can operate stand alone or it can be attached to the parsers for COBOL, PL/I and C in order to analyze embedded statements enclosed in EXEC DLI directives.
References
IMS/ESA Version 4, Application Programming: EXEC DLI Commands, IBM Corporation, Third Edition (December 1998), Document Number SC26-3063-02