Stan Kitsis : XML Schema

Inline Schemas

skits — Tue, 11 Oct 2005 04:26:00 GMT

MSDN just published my article on inline schemas. Check it out.

XML Editor in VS2005: Support for inline schemas

skits — Sat, 24 Sep 2005 02:29:00 GMT

The XML Editor provides support for Inline Schemas. Inline schemas are XML schema definitions included inside XML instance documents. They can be used to validate that the rest of the XML matches the schema constraints in the same way that external schema documents can be used. Likewise, the syntax and semantics of inline schemas are the same as for external schemas. Inline schemas can be useful in a number of situations, including:

· An architecture where internal DTDs were used and the developers wish to preserve that design pattern.

· It is difficult to access external files or URLs, e.g. for security or platform reasons.

· There is too much diversity in the set of schemas and instances that a system must process, so it is easiest to simply keep the schema as an integral part of the XML document.

The following XML snippet contains an example of using an inline schema.

<?xml version="1.0" encoding="utf-8"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"

targetNamespace="http://inline"

xmlns="http://inline"

elementFormDefault="qualified"

attributeFormDefault="unqualified">

<xs:element name="parent">

<xs:complexType>

<xs:sequence>

<xs:element name="child" type="xs:string"/>

</xs:sequence>

</xs:complexType>

</xs:element>

</xs:schema>

<inl:parent>

<inl:child>text</inl:child>

</inl:parent>

</root>

You can change the inline schema and the XML Editor will pick up those changes immediately and use the updated schema for validation and intellisense. For example, if you change the <child> element’s type from xs:string to xs:int, you will get a validation error.

XML Editor in VS 2005: Did you know?

skits — Wed, 21 Sep 2005 02:32:00 GMT

Did you know that there are multiple ways of associating a schema with an XML document in the XML Editor? The following list describes all of them in the order in which the XML Editor will look for them

Schemas Property on your XML document
Inline inside your XML document
xsi:schemaLocation or xsi:noNamespaceSchemaLocation attributes in your XML document
Open Document Window.
Anywhere in your current Project
In the Schema Cache Directory or from a Schema Catalog file.

This can be useful if you are working with multiple versions of the same schema. If the XML Editor picks a different schema than the one you want it to use for a particular XML file, then you can always override that choice by editing the Schemas Property on that XML file.

Note that if you rename the schema that your XML document is referencing, then the Schemas Property will be automatically updated to point to the new filename. And if you delete the schema that your XML document is referencing, then the Schemas Property will be cleared and the XML Editor will try to find a new schema using locations and order listed above.

XML Editor in VS2005: Schema Cache and Schema Catalogs

skits — Tue, 20 Sep 2005 04:41:00 GMT

Below are a few tips and tricks on using schema cache and schema catalogs with the new XML Editor in VS 2005.

Schema Cache

The XML Editor comes with a set of schemas that describe some of the W3C standard and some of the VS specific XML namespaces. These schemas are installed into your VS installation directory under %vsinstalldir%\xml\schemas. When you declare one of the namespacess defined by these schemas in your XML files, the XML Editor will automatically associate appropriate schema(s) from the cache location and instantly provide you with intellisense data and validation. The purpose of the schema cache directory is to hold standard schemas as well as schemas that are unlikely to change.

The following operations are supported by the XML Editor without requiring a VS restart.
- Adding schemas
- Deleting schemas
- Renaming schemas

You can also change the schema cache location. This is done by modifying Cache Directory Location on Tools | Options | Text Editor | XML | Miscellaneous dialog. When you do this, the XML Editor will stop using schemas from the old location and instead switch to the new folder.

Schema Catalogs

You can extend existing schema cache using catalog.xml file. VS installs a sample catalog.xml file (along with catalog.xsd) in the schema cache folder. This file can be used to do several things. First of all, you can associate namespaces with external locations as in the following example:

<Schema href="%VsInstallDir%/Common7/IDE/Policy/Schemas/TDLSchema.xsd"

targetNamespace="http://www.microsoft.com/schema/EnterpriseTemplates/TDLSchema"/>

You can also associate file extensions with specific namespaces. The following line taken from the sample catalog.xml associates .config files with dotNetConfig.xsd schema

Finally, you can point your catalog to another catalog file creating a chain:

Walking XmlSchema and XmlSchemaSet objects

skits — Sun, 07 Aug 2005 00:25:00 GMT

I’ve seen a number of newsgroup posts asking how to find a particular element or how to get a list of all elements from either XmlSchema or XmlSchemaSet objects. Since we don’t provide this functionality in the framework, you need to manually traverse these objects to get what you want. Depending on what your goal is, you might need to get either pre-compile or post-compile information. For example, named groups are not available post-compile while PSVI information is not available pre-compile. In this post I’ll show you how you can get pre-compile information from these objects. To make the reading easier, I don’t include any error or exception handling code which is not relevant.

I’m assuming that you have a SchemaSet with a few schemas added to it. SchemaSet provides collections of global elements, types, and attributes. However, these collections are empty until you compile the set. Note that named group collection is not available in the SchemaSet. To get the pre-compile info (including a list of named groups), you will need to go through each schema in the set.

foreach (XmlSchema schema in ss.Schemas())

{

}

Once you have an XmlSchema object, you can step through and parse each global

// stepping through global complex types

foreach (XmlSchemaType type in schema.SchemaTypes.Values)

{

if (type is XmlSchemaComplexType)

{

}

// stepping through global elements

foreach (XmlSchemaElement el in schema.Elements.Values)

{

}

// stepping through named groups

foreach (XmlSchemaAnnotated xsa in schema.Items)

{

if (xsa is XmlSchemaGroup)

{

}

Now that we have a global, whether it’s a type, an element, or a group, how do we traverse it? I’m going to use a recursive method that takes an XmlSchemaParticle to do it.

void walkTheParticle(XmlSchemaParticle particle)

{

if (particle is XmlSchemaElement)

{

XmlSchemaElement elem = particle as XmlSchemaElement;

// todo: insert your processing code here

if (elem.RefName.IsEmpty)

{

XmlSchemaType type = (XmlSchemaType)elem.ElementSchemaType;

if (type is XmlSchemaComplexType)

{

XmlSchemaComplexType ct = type as XmlSchemaComplexType;

if (ct.QualifiedName.IsEmpty)

{

walkTheParticle(ct.ContentTypeParticle);

}

else if (particle is XmlSchemaGroupBase)

//xs:all, xs:choice, xs:sequence

{

XmlSchemaGroupBase baseParticle = particle as XmlSchemaGroupBase;

foreach (XmlSchemaParticle subParticle in baseParticle.Items)

{

walkTheParticle(subParticle);

}

If the particle passed to the walkTheParticle is a base group (all, choice, or sequence), we will loop through each element within this base group. If the particle is an element, we will do our processing and then (if the element is of a complex type) walk through it. Finally, below are the last touches to the calling method to make it all work.

void start(XmlSchemaSet ss)

{

foreach (XmlSchema schema in ss.Schemas())

{

foreach (XmlSchemaType type in schema.SchemaTypes.Values)

{

if (type is XmlSchemaComplexType)

{

XmlSchemaComplexType ct = type as XmlSchemaComplexType;

walkTheParticle(ct.ContentTypeParticle);

}

foreach (XmlSchemaElement el in schema.Elements.Values)

{

walkTheParticle(el);

}

foreach (XmlSchemaAnnotated xsa in schema.Items)

{

if (xsa is XmlSchemaGroup)

{

XmlSchemaGroup xsg = xsa as XmlSchemaGroup;

walkTheParticle(xsg.Particle);

}

That’s about it. Let me know if you have any questions.