Identifiers are used throughout DAVE-ML to connect signals, functions, modification records and reference documents with each other, e.g., utID, gtID, bpID, refID, etc. These identifiers are character strings that must comply with the XML specification for Names [W3C-XML]. They must start with a character or underbar, may not start with "xml" or "XML," and may not contain colons, among other restrictions. In addition, the identifiers must be unique within a single DAVE-ML file. See the XML [W3C-XML] for more information regarding valid XML Names.