BS ISO IEC 29500-3:2015 pdf free download – Information technology – Document description and processing languages – OfficeOpen XML File Formats Part 3: Markup Compatibility andExtensibility
7.5 AlternateContent Element
An AlternateContent element shall be an element in the Markup Compatibility namespace with local name“AlternateContent” .An AlternateContent element shall not have unqualified attributes, but may havequalified attributes. The namespace of each qualified attribute shall be either the Markup Compatibility
namespace or a namespace declared as ignorable by the lgnorable attribute of this AlternateContent elementor one of its ancestors.
An AlternateContent element shall contain one or more Choice child elements, optionally followed by a singleFallback child element. No other elements in the Markup Compatibility namespace shall appear as childelements.Elements in other namespaces may appear as preceding, intervening, or trailing child elements, butthe namespace of such a child element shall be declared as ignorable.
[Note: lgnorable elements are allowed as child elements of AlternateContent to allow for future extensions tothis construct. lf AlternateContent were specified to contain only Choice and Fallback elements from theMarkup Compatibility namespace(57.5), this would prevent the use of other Markup Compatibility elementsthat would allow extension of AlternateContent in future versions of MCE. Any MCE processor that
encounters a child element of AlternateContent that is in the namespace of an intended future extension ofMCE will not fail to process the document, provided the namespace of this child element is ignorable, becauseit will discard all elements in ignorable namespaces that are not understood before making a selection between the remaining Choice and Fallback elements.end note]
[Note: The AlternateContent element can appear as the root element of a markup document. end note]
7.6 Choice Element
A Choice element shall be an element in the Markup Compatibility namespace with local name “Choice”.Parent elements of Choice elements shall be AlternateContent elements. A Choice element shall have anunqualified attribute with local name“Requires” and shall have no other unqualified attributes. The value ofthe Requires attribute shall be a whitespace-delimited list of one or more namespace prefixes, optionallyhaving leading and/or trailing whitespace.
[Note: with the exception of empty lists, the syntactical constraints associated with the Requires attribute arethe same as those associated with the MustUnderstand attribute.end note]
A Choice element may have qualified attributes. The namespace of each qualified attribute shall be either theMarkup Compatibility namespace or a namespace declared as ignorable.
A markup specification using MCE elements and attributes might designate one or more elements in thenamespaces it defines as application-defined extension elements.As described in 59,MCE processing iseffectively suspended within the content of these elements and they are passed through to the output
document generated by the MCE processor. No elements within the Markup Compatibility namespace shall bedesignated as application-defined extension elements.
[Rationale: This mechanism is intended to, but not limited to, be used by markup specifications to createextensibility points within the markup specification.end rationale]
[Note: lf the markup specification includes a schema, an extension element might be constrained by theschema to occur only in specific markup contexts.end note]
[Note: The content of an application-defined extension element might contain markup that uses MCE elementsand attributes. A consuming application might invoke an MCE processor to process the content of application-defined extension elements contained in an output document constructed by an MCE processor.end note]