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Subject: XML content validation by projection === CAM templates!!!
Validation by Projection David Orchard, Blog Many of the architectures and strategies for validation apply validity checking to a particular document with a pass or fail result on the document. This assumes that the schemas used in validation are expressive enough for all the potential versions of documents including any extensions. We've regularly seen that the Schema 1.0 wildcard limits the ability for fully describing documents. For example, it is impossible to have a content model that has optional elements in multiple namespaces with a wildcard at the end. The choice is to either have the wildcard or the elements. There is another approach to validation, called validation by projection, which effectively removes any unknown content prior to validation. It is validation of a projection of the XML document, where the projection is a subset of the xml document with no other modifications to the contents including order. Part of validation by projection is determining what to project. The simplest rule for determining what to project is: Starting at the root element, project any attributes and any elements that match elements in the content model of the current complexType and recurse into each element. [Author's note to W3C TAG: I wrote up a couple of personal blog entries on validation by projection. This seems to be a useful way of achieving forwards and backwards compatibility without relying upon schemas that have wildcards or open content models. From the TAG's definitional perspective, I'd characterize validation by projection as an architecture where the schema(s) define a Defined Text Set and an Accept Text Set that is equal to the Defined Text Set, then the process of projection is the creation and validation of the text against a generated Accept Text Set that has the original Accept Text Set plus all possible extra undefined elements and attributes.] http://www.pacificspirit.com/blog/2007/12/12/validation_by_projection_introduction See also Validation by Projection implementations: http://www.pacificspirit.com/blog/2007/12/12/validation_by_projection_implementations
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