:: Introduction ::
A tag is the main concept that differentiates a structured document from a traditional
document. Tags allow iPad users to assign computer-recognizable labels to parts
of documents. "Computer-recognizable" simply means that the computer "knows" (i.e.,
can find) the labels assigned by tags. Before the structured documents technology,
computer-recognizable labels could be assigned only to files and folders (e.g.,
file and folder names, permissions, etc.). These labels helped computer users
to search, share, and manipulate files and folders. For example, thanks to the
existence of such labels it is possible to write a software program that searches
for all files with file extension .jpg, stores them in a folder named Images,
and allows to view this folder only for a specified group of people. Most computer
users use file and folder labels to find the information of interest. No one would
dispute the usefulness of being able to assign labels to files and folders, of
being able to carry out an automatic search through these names, of being able
to restrict access to files and folders, etc. Tags extend this very useful folder-like
structure into documents and allow users to better organize and manage information
within documents. Tag-based labels substantially improve searching, formatting,
sharing, and manipulating information stored within documents.