18
XML Schema Processor for C++

This chapter contains the following sections:

• Description of XMLSchema
• Functions of XMLSchema

  See Also: Oracle9i XML Developer's Kits Guide - XDK

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XMLSchema Class

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Description of XMLSchema

The schema API is very simple: initialize, validate, ..., validate, terminate.

The validation process is go/no-go. Either the document is valid with respect to the schemas or it is invalid. When it is valid, a zero error code is returned. When it is invalid, a nonzero error code is returned indicating the problem. There is no distinction between warnings and errors; all problems are errors and considered fatal: validation stops immediately.

As schemas are encountered, they are loaded and preserved in the schema context. No schema is loaded more than once during a session. There is no clean up call similar to the XML parser function xmlclean(). Hence, if you need to release all memory and reset state before validating a new document, you must terminate the context and start over.

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Functions of XMLSchema

Table 18-1 Summary of Functions of XMLSchema

Function	Description
initialize()	Initializes Schema processor.
load()	Loads an additional Schema file.
target()	Returns target namespace URI.
terminate()	Terminates Schema Processor.
validate()	Validates an instance document against a Schema.

initialize()

Description

Initializes Schema processor. Returns error code, or 0 for success.

Syntax

uword initialize( XMLParser *parser);

Argument	Description
parser	XMLParser object used for allocating memory.

load()

Description

Explicitly loads a schema (if not already loaded); returns a pointer to the schema, new or old. It is not usually necessary to use this method, as the URL of a default schema may be passed directly to the validate method. Returns error code, 0 for success.

Syntax

uword load( oratext *uri,
            oratext *nsp,
            Schema **schema); 

Argument	Description
uri	URI of Schema, in compiler character set
nsp	Namespace of Schema (may be NULL), in compiler character set.
schema	Returned pointer to schema.

target()

Description

Return its target namespace URI given a Schema handle that is returned by load().

Syntax

oratext *target( Schema *schema);

Argument	Description
schema	Schema handle as returned by load() method.

terminate()

Description

Terminate Schema processor, tear down, free memory, and so on. Returns error code, 0 for success

Syntax

void terminate();

validate()

Description

Validates an instance document against a Schema.

Syntax

uword validate( Element *root,
                oratext *url);

Argument	Description
root	root element of the document returned by parser.getDocuemntElement()
url	URL of default schema; optional