XML in a Nutshell, 3rd Edition

Facets

In schema-speak, a facet is an aspect of a possible value for a simple data type. Depending on the base type, some facets make more sense than others. For example, a numeric data type can be restricted by the minimum and maximum possible values it could contain. But these types of restrictions wouldn’t make sense for a boolean value. The following list covers the different facet types that are supported by a schema processor:

• length (or minLength and maxLength)

• pattern

• enumeration

• whiteSpace

• maxInclusive and maxExclusive

• minInclusive and minExclusive

• totalDigits

• fractionDigits

Facets are applied to simple types using the xs:restriction element. Each facet is expressed as a distinct element within the restriction block, and multiple facets can be combined to further restrict potential values of the simple type.

Handling whitespace

The whiteSpace facet controls how the schema processor will deal with any whitespace within the target data. Whitespace normalization takes place before any of the other facets are processed. There are three possible values for the whiteSpace facet:

preserve

Keep all whitespace exactly as it was in the source document (basic XML 1.0 whitespace handling for content within elements).

replace

Replace occurrences of #x9 (tab), #xA (line feed), and #xD (carriage return) characters with #x20 (space) characters.

collapse

Perform the replace step first, then collapse multiple-space characters into a single space.

Restricting length

The length-restriction facets are fairly ...