====== XML Schema ======
XML Schema Tutorial by http://www.w3schools.com/Schema/

XML Schema is an XML-based alternative to DTDs.

An XML Schema describes the structure of an XML document.

The XML Schema language is also referred to as XML Schema Definition (XSD).

In this tutorial you will learn how to read and create XML Schemas, why XML Schemas are more powerful than DTDs, and how to use the XML Schema language in your application. 

===== Schema Tutorial =====

  * [[intro]]
  * [[why-use]]
  * [[howto]]
  * [[schema-schema]]

===== XML Schema Reference =====

==== XSD Elements ====

^ Element ^ Explanation ^
| [[all]] | Specifies that the child elements can appear in any order. Each child element can occur 0 or 1 time |
| [[annotation]] | Specifies the top-level element for schema comments |
| [[any]] | Enables the author to extend the XML document with elements not specified by the schema |
| [[anyAttribute]] | Enables the author to extend the XML document with attributes not specified by the schema |
| [[appInfo]] | Specifies information to be used by the application (must go inside annotation) |
| [[attribute]] | Defines an attribute |
| [[attributeGroup]] | Defines an attribute group to be used in complex type definitions |
| [[choice]] | Allows only one of the elements contained in the <choice> declaration to be present within the containing element |
| [[complexContent]] | Defines extensions or restrictions on a complex type that contains mixed content or elements only |
| [[complexType]] | Defines a complex type element |
| [[documentation]] | Defines text comments in a schema (must go inside annotation) |
| [[element]] | Defines an element |
| [[extension]] | Extends an existing simpleType or complexType element |
| [[field]] | Specifies an XPath expression that specifies the value used to define an identity constraint |
| [[group]] | Defines a group of elements to be used in complex type definitions |
| [[import]] | Adds multiple schemas with different target namespace to a document |
| [[include]] | Adds multiple schemas with the same target namespace to a document |
| [[key]] | Specifies an attribute or element value as a key (unique, non-nullable, and always present) within the containing element in an instance document |
| [[keyref]] | Specifies that an attribute or element value correspond to those of the specified key or unique element |
| [[list]] | Defines a simple type element as a list of values |
| [[notation]] | Describes the format of non-XML data within an XML document |
| [[redefine]] | Redefines simple and complex types, groups, and attribute groups from an external schema |
| [[restriction]] | Defines restrictions on a simpleType, simpleContent, or a complexContent |
| [[schema]] | Defines the root element of a schema |
| [[selector]] | Specifies an XPath expression that selects a set of elements for an identity constraint |
| [[sequence]] | Specifies that the child elements must appear in a sequence. Each child element can occur from 0 to any number of times |
| [[simpleContent]] | Contains extensions or restrictions on a text-only complex type or on a simple type as content and contains no elements |
| [[simpleType]] | Defines a simple type and specifies the constraints and information about the values of attributes or text-only elements |
| [[union]] | Defines a simple type as a collection (union) of values from specified simple data types |
| [[unique]] | Defines that an element or an attribute value must be unique within the scope |

==== XSD Restrictions/Facets for Datatypes ====

[[restrictions|Look at the XSD Restrictions]]

^ Constraint ^ Description ^
| enumeration | Defines a list of acceptable values |
| fractionDigits | Specifies the maximum number of decimal places allowed. Must be equal to or greater than zero |
| length | Specifies the exact number of characters or list items allowed. Must be equal to or greater than zero |
| maxExclusive | Specifies the upper bounds for numeric values (the value must be less than this value) |
| maxInclusive | Specifies the upper bounds for numeric values (the value must be less than or equal to this value) |
| maxLength | Specifies the maximum number of characters or list items allowed. Must be equal to or greater than zero |
| minExclusive | Specifies the lower bounds for numeric values (the value must be greater than this value) |
| minInclusive | Specifies the lower bounds for numeric values (the value must be greater than or equal to this value) |
| minLength | Specifies the minimum number of characters or list items allowed. Must be equal to or greater than zero |
| pattern | Defines the exact sequence of characters that are acceptable |
| totalDigits | Specifies the exact number of digits allowed. Must be greater than zero |
| whiteSpace | Specifies how white space (line feeds, tabs, spaces, and carriage returns) is handled |