Describe the attribute composition of the main database tables of the library at the top level.

The main database tables of the library and their attributes at the top level can be as follows:

1. Books

   • id — unique book identifier
   • title — book title
   • author_id — reference to the author
   • publisher_id — reference to the publisher
   • published_date — publication date
   • isbn — international standard book number
   • genre — genre
   • available_copies — number of available copies

2. Authors

   • id — unique author identifier
   • name — author's name
   • birth_date — date of birth
   • biography — brief biography

3. Publishers

   • id — unique publisher identifier
   • name — publisher's name
   • address — address
   • contact_info — contact information

4. Users

   • id — unique user identifier
   • name — name
   • email — email
   • membership_date — registration date

5. Loans

   • id — unique loan identifier
   • book_id — reference to the book
   • user_id — reference to the user
   • loan_date — loan date
   • return_date — return date
   • status — status (issued, returned, overdue)

This structure covers the main entities and relationships for the library management system.