For example, it can be a fragment of text, which is a part of chapter of a book. This semantic incompleteness is reflected in the object design by the fact that no title or heading is required for an object of the media branch. Offspring objects of the media class, representing different media types, can therefore be inserted at arbitrary places in a document object. This concept is applicable to all kinds of media types, although at the moment it is meaningful to the text object only. Consider a chapter in a textbook with an image inserted halfway.
Publication is the generic class for all types of published materials.
There are more specific classes inherited from Publication , designed to handle other specific features of different document types. All of these classes are designed based on the existing paper-based document system as found in most libraries nowadays. For compactness and simplicity purposes, several library categories are merged into one single class in our model. For example, there are normally references to other sections from one section in a textbook. Some exceptions are the Bible, a book of short stories, a condensed book, etc, which can contain other books.