Both allow for a degree of modularity in their languages, including, for example, splitting the schema into multiple files.

And both of them are, or can be, defined in RELAX NG does not have any analog to PSVI.

validating xml using schema-40

A schema is analogous to a grammar for a language; a schema defines what the vocabulary for the language may be and what a valid "sentence" is.

There are historic and current XML schema languages: The main ones (see also the ISO 19757's endorsed languages) are described below.

The Service Modeling Language (SML) provides a framework for relating multiple XSD documents to one or more documents in a single validation episode.

Since XSD supports associating data types with element and attribute content, it is also used for data binding, that is, for software components that read and write XML representations of computer programming-language objects.

The association may be achieved via markup within the XML document itself, or via some external means.

The process of checking to see if a XML document conforms to a schema is called validation, which is separate from XML's core concept of syntactic well-formedness.

DTDs are perhaps the most widely supported schema language for XML.

Because DTDs are one of the earliest schema languages for XML, defined before XML even had namespace support, they are widely supported.

Validation of an instance document against a schema can be regarded as a conceptually separate operation from XML parsing.