---
title: "Non-Deterministic Content Models | Microsoft Docs"
description: View an example of using an XML schema with a non-deterministic content model. 
ms.custom: ""
ms.date: "03/14/2017"
ms.prod: sql
ms.prod_service: "database-engine"
ms.reviewer: ""
ms.technology: xml
ms.topic: conceptual
helpviewer_keywords: 
  - "non-deterministic content models"
  - "content models [XML in SQL Server]"
ms.assetid: 9d4513e7-dd19-4491-b7c7-28bc7c2f8589
author: MightyPen
ms.author: genemi
---
# Non-Deterministic Content Models
[!INCLUDE[appliesto-ss-asdb-xxxx-xxx-md](../../includes/appliesto-ss-asdb-xxxx-xxx-md.md)]
  Before [!INCLUDE[ssVersion2005](../../includes/ssversion2005-md.md)] Service Pack 1 (SP1), [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] rejected XML schemas that had non-deterministic content models.  
  
 Beginning with [!INCLUDE[ssVersion2005](../../includes/ssversion2005-md.md)] SP1, however, non-deterministic content models are accepted if the occurrence constraints are 0,1, or unbounded.  
  
## Example: Non-deterministic content model rejected  
 The following example attempts to create an XML schema with a non-deterministic content model. The code fails because it is not clear whether the `<root>` element should have a sequence of two `<a>` elements or if the `<root>` element should have two sequences, each with an `<a>` element.  
  
```  
CREATE XML SCHEMA COLLECTION MyCollection AS '  
<schema xmlns="http://www.w3.org/2001/XMLSchema">  
    <element name="root">  
        <complexType>  
            <sequence minOccurs="1" maxOccurs="2">  
                <element name="a" type="string" minOccurs="1" maxOccurs="2"/>  
            </sequence>  
        </complexType>  
    </element>  
</schema>  
'  
GO  
```  
  
 The schema can be fixed by moving the occurrence constraint to a unique location. For example, the constraint can be moved to the containing sequence particle:  
  
```  
<sequence minOccurs="1" maxOccurs="4">  
    <element name="a" type="string" minOccurs="1" maxOccurs="1"/>  
</sequence>  
```  
  
 Or the constraint can be moved to the contained element:  
  
```  
<sequence minOccurs="1" maxOccurs="1">  
     <element name="a" type="string" minOccurs="1" maxOccurs="4"/>  
</sequence>  
```  
  
## Example: Non-deterministic content model accepted  
 The following schema would be rejected in versions of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] before [!INCLUDE[ssVersion2005](../../includes/ssversion2005-md.md)] SP1.  
  
```  
CREATE XML SCHEMA COLLECTION MyCollection AS '  
<schema xmlns="http://www.w3.org/2001/XMLSchema">  
    <element name="root">  
        <complexType>  
            <sequence minOccurs="0" maxOccurs="unbounded">  
                <element name="a" type="string" minOccurs="0" maxOccurs="1"/>  
                <element name="b" type="string" minOccurs="1" maxOccurs="unbounded"/>  
            </sequence>  
        </complexType>  
    </element>  
</schema>  
'  
GO  
```  
  
## See Also  
 [Requirements and Limitations for XML Schema Collections on the Server](../../relational-databases/xml/requirements-and-limitations-for-xml-schema-collections-on-the-server.md)