Extremely pureXML in DB2 10 for z/OS

182 Extremely pureXML in DB2 10 for z/OS

8.3.3 Validation of XML documents in COBOL

Finally, COBOL also offers validation of XML documents against an XML schema through a

variant of the XML PARSE statement. This approach requires Enterprise COBOL for z/OS

V4.2.

The schema does not have to be registered anywhere, but it does have to be in a

preprocessed format known as

Optimized Schema Representation (OSR). This preprocessing

can be done from UNIX System Services with a command such as in Example 8-26. First, the

schema is copied to UNIX System Services from TSO, and then the OSR document is

generated.

Example 8-26 Converting a schema to OSR format

cp -B "//'XMLR2.BKSTMT.XSD'" /u/xmlr2/bkstmt.xsd

xsdosrg -v -o /u/xmlr2/bkstmt.osr /u/xmlr2/bkstmt.xsd

We extend the XML PARSE statement in Example 8-25 on page 181 with the validating

phrase shown in Example 8-27.

Example 8-27 XMLPARSE with schema validation

CONFIGURATION SECTION.

SPECIAL-NAMES.

XML-SCHEMA RSCHEMA IS 'DDSCHEMA'.

...

XML PARSE RCPT

WITH ENCODING 1208

VALIDATING WITH FILE RSCHEMA

PROCESSING PROCEDURE GET-DATA

END-XML.

We use the schema declaration in the SPECIAL-NAMES section to associate the schema

name RSCHEMA with an external file that contains the schema. This association can then be

supplied as a DD statement in the JCL to run the COBOL program, as shown

inExample 8-28.

Example 8-28 DD statement for supplying a schema to the COBOL program

//GO.DDSCHEMA DD PATH='/u/xmlr2/bkstmt.osr'

As mentioned previously, the automatic schema validation that can be set up in DB2, simply

by associating an XML type identifier with the XML column, is robust to schema changes and

can be easy to work with. This choice is generally better than explicit schema validation in

both DB2 and COBOL.