Preprocess a Schema to Merge Included Schemas

The W3C XSD include element provides support for schema modularity in which an XML schema can be partitioned into more than one physical file. SQL Server currently does not support this element. XML schemas that include this element will be rejected by the server.

As a solution, XML schemas that include the <xsd:include> directive can be preprocessed to copy and merge the contents of any included schemas into a single schema for uploading to the server. The following C# code can be used for the preprocessing. The comments in the early part of the code provide information about how to use it.

// XSD Schema Include Normalizer  
// To compile:   
// csc filename.cs  
//  
// How to use:  
//  
// Arguments: [-q] input.xsd [output.xsd]  
//  
// input.xsd       - file to normalize  
// output.xsd      - file to output, default is console  
// -q              - quiet  
//   
// Example:  
//   
// filename.exe schema.xsd  
//   
using System;  
using System.Xml;  
using System.Xml.Schema;  
using System.IO;  
using System.Collections;  
public class XsdSchemaNormalizer  
{  
    private static bool NormalizeXmlSchema( String url, TextWriter writer )  
    {  
   try {  
       XmlTextReader txtRead = new XmlTextReader( url );  
       XmlSchema sch = XmlSchema.Read( txtRead, null );  
  
       // Compiling Schema  
       sch.Compile(null);  
  
       XmlSchema outSch =   
      XmlSchemaIncludeNormalizer.BuildIncludeFreeXmlSchema( sch);  
  
       outSch.Write( writer );  
   } catch ( Exception e ) {  
       Console.WriteLine(e.ToString());  
       return false;  
   }  
   return true;  
    }  
    public static void usage()  
    {  
   Console.WriteLine("Arguments: [-q] [-v] input.xsd [output.xsd]\n");  
   Console.WriteLine("input.xsd       - file to normalize");  
   Console.WriteLine("output.xsd      - file to output, default is console");  
   Console.WriteLine("-q              - quiet");  
    }  
    public static void Main(String []args)  
    {  
   if( args.GetLength(0) < 1 ) {  
       usage();  
       return;  
   }  
   int argi = 0;  
   bool quiet = false;  
   if( args[argi] == "-q" ) {  
       quiet = true;  
            argi++;  
   }  
  
   if( argi == args.GetLength(0) )  
   {  
       usage();  
       return;  
   }  
  
   String url = args[argi];  
  
   if( !quiet )  
       Console.WriteLine("Loading Schema: " + url);  
  
   if( argi < ( args.GetLength(0) - 1 ) )  
   {  
       if( !quiet )  
      Console.WriteLine("Outputing to file: " + args[argi+1]);  
  
       StreamWriter output =   
      new StreamWriter( new FileStream(args[argi+1], FileMode.Create ));  
  
       NormalizeXmlSchema( url, output);  
   }  
   else   
   {  
       NormalizeXmlSchema( url, Console.Out);  
   }  
  
    }  
}  
  
// A class to remove all <include> from a Xml Schema  
//  
public class XmlSchemaIncludeNormalizer  
{  
    // Takes as input a XmlSchema which has includes in it   
    // and the schema location uri of that XmlSchema  
    //   
    // Returns a "preprocessed" form of XmlSchema without any   
    // includes. It still retains imports though. Also, it does  
    // not propagate unhandled attributes  
    //  
    // It can throw any exception  
    public static XmlSchema BuildIncludeFreeXmlSchema( XmlSchema inSch )  
    {  
   XmlSchema outSch = new XmlSchema();  
  
   AddSchema( outSch, inSch );  
  
   return outSch;  
    }  
  
    // Adds everything in the second schema minus includes to   
    // the first schema  
    //  
    private static void AddSchema( XmlSchema outSch, XmlSchema add)  
    {  
   outSch.AttributeFormDefault = add.AttributeFormDefault;  
   outSch.BlockDefault = add.BlockDefault;  
   outSch.ElementFormDefault = add.ElementFormDefault;  
   outSch.FinalDefault = add.FinalDefault;  
   outSch.Id = add.Id;  
   outSch.TargetNamespace = add.TargetNamespace;  
   outSch.Version = add.Version;  
  
   AddTableToSchema( outSch, add.AttributeGroups );  
   AddTableToSchema( outSch, add.Attributes );  
   AddTableToSchema( outSch, add.Elements );  
   AddTableToSchema( outSch, add.Groups );  
   AddTableToSchema( outSch, add.Notations );  
   AddTableToSchema( outSch, add.SchemaTypes );  
  
   // Handle includes as a special case  
   for( int i = 0; i < add.Includes.Count; i++ )  
   {  
       if( ! ( add.Includes[i] is XmlSchemaInclude) )  
      outSch.Includes.Add( add.Includes[i] );  
   }  
    }  
  
    // Adds all items in the XmlSchemaObjectTable to the specified XmlSchema  
    //  
    private static void AddTableToSchema( XmlSchema outSch,   
                 XmlSchemaObjectTable table )  
    {  
   IDictionaryEnumerator e = table.GetEnumerator();  
  
   while( e.MoveNext() )  
   {  
       outSch.Items.Add( (XmlSchemaObject)e.Value );  
   }  
    }  
}  

Testing the Preprocessor Tool

You can use the following XSD schemas to test the preprocessor tool:

books_common.xsd

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"  
     xmlns="bookstore-schema"  
     elementFormDefault="qualified" >  
  <xsd:element name="publisher" type="xsd:string"/>  
</xsd:schema>  

books.xsd

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"  
     xmlns="bookstore-schema"  
     elementFormDefault="qualified"  
     targetNamespace="bookstore-schema">  
  <xsd:include id="books_common" schemaLocation="books_common.xsd"/>  
  <xsd:element name="bookstore" type="xsd:string" />  
</xsd:schema>  

See Also

XML Schema Collections (SQL Server)