Natural to IDL Mapping

This document describes how Natural data types are mapped to Software AG IDL files by the Software AG IDL Extractor for Natural. It covers the following topics:

For more information on Natural syntax, refer to the Natural documentation.


Mapping Natural Data Types to Software AG IDL

The IDL Extractor for Natural maps the following subset of Natural data types to Software AG IDL data types.

In the table below, the following metasymbols and informal terms are used for the IDL.

  • The metasymbols "[" and "]" enclose optional lexical entities.

  • The informal term number (or in some cases number1.number2) is a sequence of numeric characters, for example 123.

Natural Data Type Software AG IDL Data Type Description
Anumber An Alphanumeric
A DYNAMIC AVn Alphanumeric variable length
Bnumber Bnumber Binary
B DYNAMIC BV Binary variable length
C not supported  
D D Date
F4 F4 Floating point (small)
F8 F8 Floating point (large)
I1 I1 Integer (small)
I2 I2 Integer (medium)
I4 I4 Integer (large)
L L Logical
Nnumber[.number] Nnumber[.number] Unpacked decimal
Pnumber[.number] Pnumber[.number] Packed decimal
T T Time
Unumber Unumber Unicode
U DYNAMIC UV Unicode variable length

User-defined Mapping

Depending on the Natural syntax and the Natural server implementation, user interaction may be required to get correct extraction results. User interaction can also simplify or modernize the extracted IDL. As a result, the user-defined mapping is contained in a Designer file with extension .cvm that contains Natural-specific mapping information. See Server Mapping Files for Natural in the Designer documentation. The following is covered:

See Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation for more information.

Extracting the IDL Library Name

The Natural library from where Natural programs are extracted is used as the IDL library name. See library-definition under Software AG IDL Grammar in the IDL Editor documentation.

Extracting the IDL Program Name

The Natural program name is used as the IDL program name, see program-definition under Software AG IDL Grammar in the IDL Editor documentation.

Extracting IDL Parameter Names

For source extractions, Natural parameter names are kept and used as IDL parameters, see simple-parameter-definition and group-parameter-definition under Software AG IDL Grammar in the IDL Editor documentation.

For object extractions, Natural programs must be compiled (cataloged) with the compiler option SYMGEN=ON to keep original Natural parameter names. Otherwise, generic parameter names are generated (PARAMETER-1, PARAMETER-2, etc.).

In Select Natural Sources (see Step 3: Select the Natural Subprograms from NaturalONE Project if you are extracting from NaturalONE projects or Step 3: Select the Natural Subprograms if you are extracting from a Natural RPC environment), you can choose special characters ($, #, &, @, /, £, æ, Æ, ø, Ø, å, Å) in Natural parameter names to be replaced by underscores. See Rules for Coding Group and Parameter Names.

Extracting IDL Directions (IN,OUT,INOUT)

In most Natural subprograms, parameters have no specification for a direction. Missing a direction is unproblematic for local calls. For remote RPC calls, however, specifying the direction helps to reduce data sizes.

If you redesign the interface, you can define IDL directions in Step 6: Redesign the Interface for Natural Subprograms (Optional) using the mapping operations Map to In, Map to Out, Map to InOut.

Otherwise, IDL directions can be inserted at top-level parameters (level 1) using a Natural line comment in the Natural subprogram (CALLNAT) interface definition (DEFINE DATA PARAMETER), example:

DEFINE DATA PARAMETER
1 #IN-FIELD-1            (P9)  /* IN
1 #OUT-FIELD-1           (P9)  /* OUT
1 #INOUT-FIELD-1         (P9)  /* INOUT
1 #INOUT-FIELD-2         (P9)
1 #IN-GROUP-1                  /* IN
  2 #IN-GROUP-FIELD-1    (A10)
1 #OUT-GROUP-1                 /* OUT
  2 #OUT-GROUP-FIELD-1   (A10)
1 #INOUT-GROUP-1               /* INOUT
  2 #INOUT-GROUP-FIELD-1 (A10)
1 #INOUT-GROUP-2              
  2 #INOUT-GROUP-FIELD-2 (A10)
1 #INOUT-GROUP-3        
  2 #INOUT-GROUP-FIELD-3 (A10) /* OUT
END-DEFINE

If no direction is specified (such as in #INOUT-FIELD-2 and #INOUT-GROUP-2 in the example above), the default direction INOUT applies.

Specifications on a level greater than 1 (such as #INOUT-GROUP-FIELD-3 in the example above) are ignored. Note that in IDL directions are specified on top-level fields (level 1), see attribute-list under Software AG IDL Grammar in the IDL Editor documentation.

Specifications on IDL directions are only considered when extracting from a source. If you are extracting from an object (compiled), as described in Step 5: Select Natural Subprograms from RPC Environment, the default direction INOUT always applies.

Extracting Natural REDEFINES

A redefinition is a second parameter layout of the same memory portion. The parameter #BASE-FIELD is redefined by the fields FILLER-1 thru R-P3-01.

DEFINE DATA PARAMETER
1 #BASE-FIELD            (A161)
1 REDEFINE #BASE-FIELD
  2 FILLER-1             (A4)
  2 FILLER-2             (A60)
  2 R-P1-01              (A1) 
  2 R-P2-01              (A10)
  2 R-P3-01              (I4)
END-DEFINE

With the extractor wizard you can select a single redefine path for IDL usage (here the fields FILLER-1 thru R-P3-01) if you redesign the interface. See Extracting Natural REDEFINES and Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation.

Extracting Multiple Interfaces

Legacy Natural subprograms often implement multiple functions in a single Natural subprogram. The function executed is often controlled by a so-called function code or operation-code field. See Extracting Multiple Interfaces under Examples for Redesigning the Extracted Interfaces.

With the extractor wizard you can extract the functions from the server as separate interfaces (IDL programs). In this way, the legacy server with a single physical interface can be

  • turned into a web service with operations, where the legacy functions match operations.

  • called with an object-oriented wrapper such as the Java Wrapper, the .NET Wrapper or the DCOM Wrapper, where the legacy functions match methods.

Note that every function in the Natural subprogram may have a different interface described with REDEFINE syntax. Therefore, multiple interface extraction is often combined with Extracting Natural REDEFINES.

For more information, see Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation.

Extracting Natural Arrays, Groups, X-Arrays and Variable Arrays

This section describes IDL mapping for Natural arrays and groups:

Arrays and Groups with Fixed upper Limits

Ordinary Natural arrays and groups with fixed/bound upper limits are mapped to Software AG IDL fixed-bound-array definitions, see array-definition under Software AG IDL Grammar in the IDL Editor documentation.

Natural syntax example:

DEFINE DATA PARAMETER
1 #ARRAY1   (I4/1:10) /* lower bound is fixed at 1, upper bound is 10
1 #ARRAY2   (A5/10)   /* shortcut for (A5/1:10)
1 #GROUP1   (10)      /* shortcut for (1:10)
  2 #FIELD1 (I2)
  2 #FIELD2 (A10)
. . .
END-DEFINE

X-Arrays and X-Groups

For X-arrays (eXtensible arrays) the number of occurrences is flexible at runtime. The number of occurrences can be resized, that is, increased or reduced. It is defined by specifying an asterisk (*) for index bounds.

Natural syntax example:

DEFINE DATA LOCAL
1 #X-ARRAY1 (A5/1:*) /* lower bound is fixed, upper bound is variable
1 #X-ARRAY2 (A5/*)   /* shortcut for (A5/1:*)
. . .
END-DEFINE

Natural X-arrays are mapped to Software AG IDL unbounded-array definitions, see array-definition.

Natural X-arrays with variable lower bounds are not supported by Software AG RPC technology, example:

DEFINE DATA PARAMETER
1 #X-ARRAY1 (A5/*:10) /* lower bound is variable, upper bound is fixed 
. . .
END-DEFINE

Variable Arrays and Variable Groups

In a Natural parameter data area (PDA), you can specify an array or group with a variable number of occurrences. This is done with the index notation 1:V. The maximum number of occurrences for such an array is either passed to the subprogram using an extra parameter such as #ARRAY1-LIMIT (see example below), or it can be accessed using the system variable *OCCURRENCE.

Natural syntax example:

DEFINE DATA PARAMETER
1 #ARRAY1-LIMIT (I4) /* extra parameter to pass the upper limit
1 #ARRAY1       (I4/1:V)
. . .
END-DEFINE

Natural variable arrays are mapped to Software AG IDL unbounded-array definitions, see array-definition.

If the Natural server program uses a separate parameter such as #ARRAY1-LIMIT (see the example above) instead of *OCCURRENCE to determine the upper bound limit, it is required to extract this extra parameter, too. At runtime, it is also required to specify the number of occurrences in a calling RPC client.

In a Natural server program, Natural variable arrays

  • cannot be resized for direction INOUT, which means you can only reply the same number of occurrences to the RPC client.

  • cannot be used for direction OUT either, because they cannot be created (instantiated). You may get error 10204008 during extraction.

Arrays and Groups with Mixed Dimensions (X, Variable and Fixed)

Natural arrays and groups with a mixture of fixed variable and eXtensible dimensions are not supported by Software AG RPC technolgy, example:

DEFINE DATA PARAMETER
1 #ARRAY1   (I4/1:10,1:*) /* first dimension fixed and second eXtensible
1 #ARRAY2   (I4/1:10,1:V) /* first dimension fixed and second variable
1 #ARRAY3   (I4/1:V,1:*)  /* first dimension variable and second eXtensible
. . .
END-DEFINE

Extracting Natural Structure Information (IDL Levels)

Source Extractions

Natural levels are always kept. This means that the structure in the extracted IDL is the same as in the original Natural program.

Object Extractions

  • UNIX or Windows
    In UNIX or Windows RPC environments, Natural levels are not kept. The IDL is extracted in a flat way, where

    • all IDL parameters are at level 1

    • all Natural groups are removed

    • Natural fields within groups using repetition (PERIODIC GROUPS) are mapped to IDL arrays

    • the dimension of Natural arrays within groups using repetion (PERIODIC GROUPS) is increased in the IDL. For example, a one-dimensional array may become a two-dimensional or three-dimensional IDL array depending on the dimension of the group

  • z/OS
    In z/OS RPC environments, the Natural programs must be compiled (cataloged) with the compiler option SYMGEN=ON to keep Natural levels, otherwise flat extraction is carried out.

Extracting Parameters defined with OPTIONAL

For a parameter defined without OPTIONAL, a value must be passed from the invoking Natural object, that is, the caller.

For a parameter defined with OPTIONAL, a value can, but need not be passed from the invoking Natural object to this parameter. With the SPECIFIED option, a Natural server can find out at runtime whether an optional parameter has been defined or not.

The IDL Extractor for Natural ignores the OPTIONAL specification, that is, the parameter is extracted as without the OPTIONAL specification. See the Natural documentation for more information.

EntireX RPC technology does not support optional IDL parameters. Using pure Natural RPC (Natural client to Natural server), Natural optional parameters are supported.

Setting Natural Parameters to Constants

Setting parameters to constant values and suppressing them in the IDL is part of the redesign process of the extracted interface. This keeps the IDL client interface lean. See Set Constant in the IDL Extractor for Natural documentation.

EntireX and Natural RPC make sure the constant value is passed to the Natural server at runtime.

For more information, see Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation.

Suppressing Natural Parameters

Hiding or suppressing unneeded parameters in the IDL is part of the redesign process of the extracted interface. This keeps the IDL client interface lean and minimizes the amount of data to be transferred during runtime.

EntireX and Natural RPC make sure to provide low values as input for suppressed parameters to the Natural server called (blank for IDL type A, zero for numeric data types such as IDL I, N and P). No data is transferred between an RPC client and the RPC server.

For more information, see Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation.

Renaming a Program

Renaming a program to a different name in the IDL is part of the redesign process of the extracted interface. You can adjust the short Natural name to a meaningful longer name for better readability. See Extracting Multiple Interfaces where the original Natural name CALC is renamed to IDL names ADD, SUBTRACT, MULTIPLY etc.

EntireX and Natural RPC make sure the original Natural server is called at runtime. For more information, see Step 6: Redesign the Interface for Natural Subprograms (Optional) in the IDL Extractor for Natural documentation.