Table of contents

Appendices

5.1 Errors in Schema Construction and Structure

Before assessment can be attempted, a schema is required. Special-purpose applications are free to determine a schema for use in assessment by whatever means are appropriate, but general purpose processors should implement the strategy set out in [Schema Document Location Strategy], starting with the namespaces declared in the document whose assessment is being undertaken, and the actual values of the xsi:schemaLocation and xsi:noNamespaceSchemaLocation [attributes] thereof, if any, along with an other information about schema identity or schema document location provided by users in application-specific ways, if any.

It is an error if a schema and all the components which are the value of any of its properties, recursively, fail to satisfy all the relevant Constraints on Schemas set out in the last section of each of the subsections of [Schema Component Details].

If a schema is derived from one or more schema documents (that is, one or more [schema] element information items) based on the correspondence rules set out in [Schema Component Details] and [Schemas and Namespaces: Access and Composition], two additional conditions hold:

• It is an error if any such schema document would not be fully valid with respect to a schema corresponding to the [Schema for Schemas (normative)], that is, following schema-validation with such a schema, the [schema] element information items would have a [e-validation_attempted] property with value full or partial and a [e-validity] property with value valid.

• It is an error if any such schema document is or contains any element information items which violate any of the relevant Schema Representation Constraints set out in [Schema Representation Constraints].

The three cases described above are the only types of error which this specification defines. With respect to the processes of the checking of schema structure and the construction of schemas corresponding to schema documents, this specification imposes no restrictions on processors after an error is detected. However assessment with respect to schema-like entities which do not satisfy all the above conditions is incoherent. Accordingly, conformant processors must not attempt to undertake assessment using such non-schemas.