Factors Determining Arrangement of Documents:

Documents can be arranged in various ways in a library, e.g., by author, or by title, or by, subject or by basis such as size, language, colour of binding or any other such criterion. The needs of the readers may be the criterion one can consider for arrangement of documents in a library. Mills, in his book Modern Outline of Library Classification, lists the following possible characteristics determining the arrangements of documents: 

i) Age of reader: Children's books are distinguished from adult's books.
ii) Conditions attached to the use of the material: Books for lending are distinguished from those to be consulted within the library. Generally "Reference Books" come under this category.

iii) Documents of unusual size: Documents of an abnormal size, oversize or undersize, are shelved separately. This is done to conserve space in the stack area. 

iv) Documents of unusual gross body: Micro cards, gramophone records, tapes, slides and other audio-visual material and electronic documents are shelved separately.

v) Thought content of the document (subject matter): Factual literature is arranged by subject, imaginative literature by language or author.

vi) Language of the document: Documents in foreign languages are separately arranged in their original languages.

vii) Value of the document: Manuscripts and rare and costly documents are shelved separately.

viii) Peculiarities of form of presentation: Files of bound periodicals are separately shelved.

ix) Date of printing: Incunabula - early printed books - are shelved separately.

x) Local history collection: Documents dealing with various aspects of a place, locality or region are shelved separately.

xi) Gift collection: A large number of hooks may be gifted with the condition to shelve them separately.

The above factors influence the arrangement of documents in libraries. But thought content or subject arrangement (fifth in Mill's list) is still the dominant and important facto- for deciding the sequence of documents. All other factors in the above list are functional. Though a collection can be divided into several sections on the basis of any of the above functional factors, it would still be helpful to arrange documents in each section on the basis of subject matter. This leads to parallel sequences in the various collections in libraries. In any library, the total collection gets divided into some separate collections of general books and reference books, textbooks, journals, etc. There are, thus, many sequences of books on one and the same subject in the library. These sequences are known as "parallel sequences".