Editing XML schema (section)

==== Advantages over RELAX NG ====
{{See also|XML Schema (W3C)#Criticism}}
RELAX NG does not have any analog to [[PSVI]]. Unlike W3C XML Schema, RELAX NG was designed so that validation and augmentation (adding type information and default values) are separate.

W3C XML Schema has a formal mechanism for attaching a schema to an XML document, while RELAX NG intentionally avoids such mechanisms for security and interoperability reasons.

RELAX NG has no ability to apply default attribute data to an element's list of attributes (i.e., changing the XML info set), while W3C XML Schema does. Again, this design is intentional and is to separate validation and augmentation.<ref>While annotations in RELAX NG can support default attribute values, the RELAX NG specification does not mandate that a validator provide this ability to modify an XML infoset as part of validation. The WXS specification does mandate this behavior. An additional specification associated with RELAX NG does provide this ability. See [http://www.oasis-open.org/committees/relax-ng/compatibility.html#default-value Relax NG DTD Compatibility (default value)].</ref>

W3C XML Schema has a rich "simple type" system built-in (xs:number, xs:date, etc., plus derivation of custom types), while RELAX NG has an extremely simplistic one because it is meant to use type libraries developed independently of RELAX NG, rather than grow its own. This is seen by some as a disadvantage. In practice it is common for a RELAX NG schema to use the predefined "simple types" and "restrictions" (pattern, maxLength, etc.) of W3C XML Schema.

In W3C XML Schema a specific number or range of repetitions of patterns can be expressed whereas it is practically not possible to specify at all in RELAX NG (<oneOrMore> or <zeroOrMore>).