Validation using s9api

The s9api interface allows schemas to be loaded into a Processor, and then to be used for validating instances, or for schema-aware XSLT and XQuery processing.

The main steps are:

  1. Create a net.sf.saxon.s9api.Processor.

  2. Call the newSchemaCompiler() method to get an XsdCompiler. It is possible to get multiple schema compilers, or to use a single schema compiler to compile multiple schemas.

  3. If required, set options on the XsdCompiler to control the way in which schema documents will be loaded. It is possible to set the XSD version (to 1.0 or 1.1) and to provide user-written callbacks for reporting schema errors and for URI resolution.

  4. Construct an XsdSchema object, representing a compiled schema, by calling one of the various compile() methods. The resulting schema document is available to all applications run within the containing Processor.

  5. To validate an instance document, first call the newValidator() method on the XsdSchema object. This returns a SchemaValidator.

  6. Set options on the SchemaValidator to control the way in which a particular validation episode is performed, and then invoke its validate() method to validate an instance document. Options available include the ability to control whether additional schema components can be referenced from the instance document using xsi:schemaLocation attributes, and control over the reporting of any validity errors encountered. It is also possible to set a Destination for the validated document: this will be the original source document, augmented with defaulted elements and attributes as defined in the schema, and with type annotations indicating the types associated with each element and attribute. These type annotations are particularly relevant when the instance document is then processed using a schema-aware query or stylesheet.

  7. It is possible to save a compiled schema in an SCM (schema component model) file using the method exportComponents() on the XsdSchema object (typically supplying a Serializer as the destination), and to import a previously-saved schema by calling XsdCompiler.importComponents().

  8. If the schema is to be imported into a schema-aware XSLT stylesheet, XQuery, or XPath expression, it can be supplied to the relevant XsltCompiler, XQueryCompiler, or XPathCompiler via its useSchema() method.

Note that additional schemas referenced from the xsi:schemaLocation attributes within the source documents will be loaded as necessary: see Using xsi:schemaLocation. By default a target namespace is ignored if there is already a loaded schema for that namespace; Saxon makes no attempt to load multiple schemas for the same namespace and check them for consistency. This behaviour can be changed using the configuration option MULTIPLE_SCHEMA_IMPORTS.

Unlike Saxon versions prior to Saxon 13, compiling a schema does not make it globally available to all applications using a given Processor. Each compiled schema is distinct and can be used individually without interfering with other schemas. However, all the schemas used within a Processor must be consistent. Consistency is defined in the version 4.0 language specifications: in simplified terms, it means that the same name must not be used in different schemas to refer to different element or type declarations.

The SchemaValidator implements the Destination interface, which means it can be used to receive input from any process that writes to a Destination, for example an XSLT transformation or an XQuery query. The result of validation can also be sent to any Destination, for example an XSLT transformer.