which is a content system, the librarians don't care about the structure of each individual book. They neither notice nor encode this structure. Rather, they code the structure among books, put it on little cards (digital cards or paper ones), and make it available to visitors. On the other hand, if you are managing a database of short landmark descriptions that are destined to be used in a variety of travel brochures and sites, you may very well need to know and manage the structure of your content at the sentence level. In any case, you should understand that there is a level of the structure below which you need not concern yourselfInner structure: The structure that you find represented within a content component isthe inner structure. In my library example, you can say that each book is a component. The table of contents and index within each book are the inner structures of these components. Librarians today generally don't care about the table of contents of the books that they manage. But this doesn't mean that people never care about internal structure at all. Imagine a day when a librarian decides to make a master table of contents for the entire library. The book is still the basic component in the system; now,however, the tables of contents, which are still inner structures, are of interest. The librarian must now access and combine them. The key point with inner structure is that it's part of a component, stored within it, and always travels with it--whether you notice it or notOuter structure: This structure is what relates one component to another. In the libraryexample, the card catalogue is the outer structure that organizes the cards (and the books they represent) into a useful system. You always care about outer structure. Interestingly, you may store the outer structure inside or outside the component. In thelibrary, in fact, you store it both within and outside the component: One paper card with the catalogue number for the book, or its equivalent, is inside every book, and one record is in the catalogue database. In electronic systems, you often store outer structure outside the components themselves. For example, you commonly create a hierarchy that shows how each component is related to its peers and parentsStructure is the key to managing content. Control the structure and you control the content and its publication, which, of course, is easier said than done, as the following list attests:Structure is often buried in the formatting of source content. Even if the formatting is consistent, which it often isn't, extracting the structure and making it explicit in a set of tags or database fields may prove difficult. Although consistent, the structure based on formatting alone may be ambiguous, incomplete, unintended, or inaccurate.