:: 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.