author and title are strings, with one-to-one relationships between books and authors and books and titles. More complex relationships are possible, of course.

bookcover_image is defined outside the <table> tag, which indicates that the property is transient and maintained outside the database. The property is defined as a file type, maintained on the file system, as follows:

property-type="atg.repository.FilePropertyDescriptor"

As described in the Storing Content on a File System section, this property type indicates that the repository should use the property’s path name and convert it to a java.io.File object.