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wildcard-components-and-content-validation.md

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title Wildcard Components and Content Validation | Microsoft Docs
ms.custom
ms.date 03/01/2017
ms.prod sql
ms.prod_service database-engine
ms.component xml
ms.reviewer
ms.suite sql
ms.technology xml
ms.tgt_pltfrm
ms.topic conceptual
helpviewer_keywords
wildcard components [XML]
content validation [XML]
ms.assetid ffa7d974-3645-446c-8425-f0b22b6b060a
caps.latest.revision 13
author douglaslMS
ms.author douglasl
manager craigg

Wildcard Components and Content Validation

[!INCLUDEtsql-appliesto-ss2008-xxxx-xxxx-xxx-md] Wildcard components are used to increase flexibility in what is allowed to appear in a content model. These components are supported in the XSD language in the following ways:

  • Element wildcard components. These are represented by the <xsd:any> element.

  • Attribute wildcard components. These are represented by the <xsd:anyAttribute> element.

Both wildcard character elements, <xsd:any> and <xsd:anyAttribute>, support the use of a processContents attribute. This lets you specify a value that indicates how XML applications handle the validation of document content associated with these wildcard character elements. These are the different values and their effect:

  • The strict value specifies that the contents are fully validated.

  • The skip value specifies that the contents are not validated.

  • The lax value specifies that only elements and attributes for which schema definitions are available are validated.

Lax Validation and xs:anyType Elements

The XML Schema specification uses lax validation for elements of the anyType type. Because [!INCLUDEssVersion2005] did not support lax validation, strict validation was applied for elements of the anyType. Beginning with [!INCLUDEssKatmai], lax validation is supported. Content of elements of type anyType will be validated using lax validation.

The following example illustrates the lax validation. The schema element e is of the anyType type. The example creates typed xml variables and illustrates the lax validation of the element of the anyType type.

CREATE XML SCHEMA COLLECTION SC AS '  
<schema xmlns="http://www.w3.org/2001/XMLSchema"   
        targetNamespace="http://ns">  
   <element name="e" type="anyType"/>  
   <element name="a" type="byte"/>  
   <element name="b" type="string"/>  
 </schema>'  
GO

The following example succeeds, because the validation of <e> is successful:

DECLARE @var XML(SC)  
SET @var = '<e xmlns="http://ns"><a>1</a><b>data</b></e>'  
GO

The following example succeeds. The instance is accepted, even though no element <c> is defined in the schema:

DECLARE @var XML(SC)  
SET @var = '<e xmlns="http://ns"><a>1</a><c>Wrong</c><b>data</b></e>'  
GO

The XML instance in the following example is rejected, because the definition of the <a> element does not allow a string value.

DECLARE @var XML(SC)  
SET @var = '<e xmlns="http://ns"><a>Wrong</a><b>data</b></e>'  
SELECT @var  
GO

See Also

Requirements and Limitations for XML Schema Collections on the Server