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Automated, Command Descriptor Structure Generation

IP.com Disclosure Number: IPCOM000081579D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Frender, WD: AUTHOR [+3]

Abstract

Access Method Services (AMS) is a command language processor: it executes services by command (such as PRINT, COPY, DELETE, etc.), upon objects such as data sets and catalogs. Each command conforms to a basic command language syntax. In order to accommodate extensions to the set of commands executable by AMS, a generalized parsing routine, which employs tables that describe the appropriate syntax of each specific command, is employed. These tables, known as "Command Descriptors", are generated by a special AMS command, COMGEN.

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Automated, Command Descriptor Structure Generation

Access Method Services (AMS) is a command language processor: it executes services by command (such as PRINT, COPY, DELETE, etc.), upon objects such as data sets and catalogs. Each command conforms to a basic command language syntax. In order to accommodate extensions to the set of commands executable by AMS, a generalized parsing routine, which employs tables that describe the appropriate syntax of each specific command, is employed. These tables, known as "Command Descriptors", are generated by a special AMS command, COMGEN.

Described herein is an implementation of the COMGEN function. In order to provide context, the following description of the AMS processor (Fig. 1) is provided. (The parsing function within AMS is called the "Reader/Interpreter").

An Invoking Program (normally the OS Supervisor - in response to an EXEC, JCL command) transfers control to the AMS Executive 11, which after initializing the environment, transfers control to the Reader/Interpreter (R/I) 12. The R/I accesses the command input stream (normally SYSIN), in order to collect the character string which comprises the full source command 14. The syntax of AMS is such that each command is uniquely identified by the first keyword scanned-out, this keyword being known as the Verb. R/I 12 searches the Verb Table, Fig. 2, (stored in the same library 16, normally SYSLIB, as the Command Descriptors) in order to determine: 1) Whether the verb is recognizable; and

2) The name of the Command Descriptor associated with the

verb.

Upon determining the name (IDCCDxx, where xx is unique for each command), the Command Descriptor is loaded by R/I 12. Using the information therein, see Fig. 3, R/I 12 parses the source command 14 and builds an in-core table known as the Function Definition Table (FDT) 18, which is an encoded representation of the actual parameter values found in the source command 14. The FDT 18 is the "output" of the R/I 12, and is passed on to the Function Support Routine (FSR) 20 responsible for the given command. The name of the FSR is contained within the Command Descriptor; the R/I 12 extracts this name and returns it to the Executive 11 along with the FDT 18.

The Executive 11 now invokes the required FSR and passes the FDT to the FSR. The FSR accesses the FDT fields (encoded parameters) in accord with a "symbolic...