Arrays and Chains:

Isolates are arranged in what are called arrays and chains. ,An array is a sequence of coordinate (equally ranked) classes arranged in some definite order. Ranganathan defines array as "a set of classes arranged in the proper sequence and derived from a universe, on the basis of a single characteristic at any step in the progress towards a complete assortment of the entities of the universe". For example, all the student of BLIScoutse, when arranged in some order, say by roll number, or alphabetically by name or in order of merit, form an array.' Similarly, the sons and daughters of the same parents are said to form an array. All th4 continents of the world form an array; and all countries of the world when arranged in some order form an array. The army of classes, in its turn, can be an open array when admitting of extrapolation and a closed array when. not admitting of extrapolation. A systematic or utilitarian arrangement of members of an array is called Helpful Sequence. This arrangement is called helpful,as it is helpful to the majority of the classification users  though not to all. Broader groups in an array are arranged in what is called a Filiatory Sequence. It means placing together closely related .classes. The order of main classes in J.D. Brown's Subject Classification (1906) is in the evolutionary order of matter 7 force - life - mind - record.  

A chain is the sequence of class6s of a universe consisting of a class and of its universe of successive removes, carried backwards  to any point desired-that is, all the members are of unequal rank and are arranged in the order of constantly decreasing extension and increasing intension. The order in a chain is from general to specific or in the reverse order of specific to general. For example, the World, Asia, India, Maharashtra, Mumbai form a chain of classes in this or reversed order. Similarly social sciences, economics, finance, money, banks form another chain of classes. Your grandfather, your father, and you form a chain of classes, but all your brothers and sisters form an array of classes. The arrangement of entities in a chain is always hierarchical.