29. The method of claim 26 , wherein: the reference includes one or more in-band values that are interpreted to define the identified glyphlet.
26. A computer-implemented method of representing a character in a text document, comprising: performing operations by a programmable processor of a computer, comprising: inserting into the text document a reference identifying a glyphlet, the identified glyphlet stored in a memory of the computer being a data structure including both a set of one or more character attributes defining semantic information of a character and a set of one or more glyph attributes defining appearance information from which a glyph image of a glyph representing the character can be rendered, the glyph attributes including all the information necessary to render the glyph image, the reference representing the character in the text document; and displaying the character in the text document, the displayed character being rendered from the glyph attributes.