LCID, Guid, Tag, and RefOrder

Four of the child elements for the <Source> element support important functionality for consuming applications that generate bibliographies using an externally defined stylesheet. The <LCID> element describes the language to be used when displaying the bibliography entry. This piece of data provides an instruction to the consuming application on the grammar of the citations and bibliography (including international name formats, date formats, and punctuation marks).

The <Guid> and <Tag> elements can be leveraged if an application wishes to uniquely identify the bibliography entry described in the <Source> element. For example, when a Source element is brought into a document and the <Tag> value for that <Source> element matches that of another Source element already in the document, the existing Source elements values could be overwritten with the new Source element. Two <Source> elements with the same <Tag> element value cannot exist in the same document. GUIDs can then be used in conjunction with Tags to indicate whether a <Source> element has been edited. When a <Source> element from one document has been edited, an application may decide to apply the edits to matching <Source> elements in other documents.

The <RefOrder> element for a source indicates the position, in numeric sequence, for the first reference to the source within the document text. This information is used in bibliography styles that sort sources by order in the document rather than alphabetical order.