Schema validation

Tutorials
This article is one several tutorials, guides, and annotated examples available in this wiki.
Multipage tutorials:  • COLLADA DOM user guide Shorter how-tos:  • Using accessors  • Schema validation • Using URIs  • Various annotated examples Instructions for adding a tutorial

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The COLLADA format is defined by a W3C schema. If a document doesn't conform to the schema then it isn't valid COLLADA data. This tutorial explains a few different ways to validate a COLLADA document against the COLLADA schema.

Using xmllint

xmllint is a command-line application that can be used to validate an XML document against a W3C schema. xmllint is distributed as part of libxml. You can find binaries for Windows here. Mac OS X and most Linux distributions come with libxml already installed.

To validate the COLLADA document duck.dae against the latest COLLADA 1.4 schema available from Khronos, run the following command:

xmllint --noout --schema http://www.khronos.org/files/collada_schema_1_4_1.xsd duck.dae

You could also copy the schema locally and use your local version:

xmllint --noout --schema colladaSchema.xsd duck.dae

The --noout option prevents superfluous output. If the COLLADA document violates the schema, xmllint outputs an error message.

Using libxml from a C/C++ Application

Using libxml, you can validate a COLLADA document against the schema from a C/C++ application. The following code illustrates how it works.

#include "libxml/xmlschemas.h"

// libxml error handler
void schemaErrorCallback(void*, const char* message, ...) {
  va_list varArgs;
  va_start(varArgs, message);
  vfprintf(stdout, message, varArgs);
  va_end(varArgs);
}

// libxml warning handler
void schemaWarningCallback(void* callbackData, const char* message, ...) {
}

// Returns true if file validated successfully, false otherwise
bool validate(const string& uri) {
  bool result = false;
  if (xmlSchemaParserCtxt* schemaParser = 
     xmlSchemaNewParserCtxt("http://www.khronos.org/files/collada_schema_1_4_1.xsd")) {
    if (xmlSchema* schema = xmlSchemaParse(schemaParser)) {
      if (xmlSchemaValidCtxt* validityContext = xmlSchemaNewValidCtxt(schema)) {
        xmlSchemaSetValidErrors(validityContext,
                               schemaErrorCallback,
                               schemaWarningCallback,
                               /* callback data */ 0);

        // Returns 0 if validation succeeded
        result = xmlSchemaValidateFile(validityContext, uri.c_str(), 0) == 0;
        xmlSchemaFreeValidCtxt(validityContext);
      }
      xmlSchemaFree(schema);
    }
    xmlSchemaFreeParserCtxt(schemaParser);
  }

  return result;
}