Page 25 - DLIS405_INFORMATION_STORAGE_AND_RETRIEVAL

Information Storage and Retrieval

Notes developed hierarchies, and a rich network of relationships among topics. In the DDC, basic classes
are organized by disciplines or fields of study. At the broadest level, the DDC is divided into ten
main classes, which together cover the entire world of knowledge.
Each main class is further divided into ten divisions, and each division into ten sections (not all the
numbers for the divisions and sections have been used). The main structure of the DDC is presented
in the DDC Summaries following this introduction. The headings associated with the numbers in
the summaries have been edited for browsing purposes, and do not necessarily match the complete
headings found in the schedules.
The first summary contains the ten main classes. The first digit in each three-digit number represents
the main class. For example, 600 represent technology.

The second summary contains the hundred divisions. The second digit in each three-digit number
indicates the division. For example, 600 is used for general works on technology, 610 for medicine
and health, 620 for engineering, 630 for agriculture.
The third summary contains the thousand sections. The third digit in each three-digit number
indicates the section. Thus, 610 is used for general works on medicine and health, 611 for human
anatomy, 612 for human physiology, 613 for personal health and safety.

Hierarchy
Hierarchy in the DDC is expressed through structure and notation. Structural hierarchy means that
all topics (aside from the ten main classes) are part of all the broader topics above them. Any note
regarding the nature of a class holds true for all the subordinate classes, including logically
subordinate topics classed at coordinate numbers.
Notational hierarchy is expressed by length of notation. Numbers at any given level are usually
subordinate to a class whose notation is one digit shorter; coordinate with a class whose notation
has the same number of significant digits; and super ordinate to a class with numbers one or more
digits longer. The underlined digits in the following example demonstrate this notational hierarchy:
600 Technology
630 Agriculture and related technologies
636 Animal husbandry
636.7 Dogs
636.8 Cats
“Dogs” and “Cats” are more specific than (i.e., are subordinate to) “Animal husbandry”; they are
equally specific as (i.e., are coordinate with) each other; and “Animal husbandry” is less specific
than (i.e., is super ordinate to) “Dogs” and “Cats.” Sometimes, other devices must be used to express
the hierarchy when it is not possible or desirable to do so through the notation. Special headings,
notes, and entries indicate relationships among topics that violate notational hierarchy.

2.4.7 Arrangement of the DDC

The print version of the latest full edition of the DDC, Edition 22, is composed of the following
major parts in four volumes:
Volume 1
(A) New Features in Edition 22: A brief explanation of the special features and changes in DDC 22.
(B) Introduction: A description of the DDC and how to use it.
(C) Glossary: Short definitions of terms used in the DDC.

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