# Schema Processing 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 Processor (`net.sf.saxon.s9api.Processor`) and call its `getSchemaManager()` method to get a SchemaManager.

2. If required, set options on the SchemaManager to control the way in which schema documents will be loaded.

3. Load a schema document by calling the `load()` method, which takes a JAXP Source object as its argument. The resulting schema document is available to all applications run within the containing `Processor`.

4. To validate an instance document, call the `newSchemaValidator` method on the `SchemaManager` object.

5. 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.

Note that additional schemas referenced from the `xsi:schemaLocation` attributes within the source documents will be loaded as necessary. 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.

Although the API is defined in such a way that a `SchemaValidator` is created for a particular `SchemaManager`, in the Saxon implementation the schema components that are available to the validator are not only the components within that schema, but all the components that form part of any schema registered with the `Processor` (or indeed, with the underlying `Configuration`)

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.

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