Trends in Library Classification.

I. Historical Development and Theoretical Trends

The evolution of classification schemes is recognized in three distinct periods, as identified by Ranganathan:

1. Pre-facet Period (1876–1896): This period saw the publication of early schemes such as Melvil Dewey's Decimal Classification (1876) and C.A. Cutter's Expansive Classification (1879).
2. Transition to Facet Period (1897–1932): Schemes published during this time include the Universal Decimal Classification (UDC) (1897–1905) and the Library of Congress Classification (LC) (1902).
3. Facet Period (1933–1972): This period was defined by the emergence of fully faceted and analytico-synthetic schemes, starting with Ranganathan's Colon Classification (CC) (1933), along with ILE. Bliss's Bibliographic Classification (1935).

A key intellectual trend spanning these periods has been the shift from descriptive and empirical theories to a dynamic and systematic theory. This dynamic theory, largely propounded by Ranganathan, emphasizes the use of canons, postulates, and principles to guide scheme design, making classification an objective and scientific discipline.

II. Methodological and Structural Trends

The complexity of the Universe of Subjects (UoS), which is described as infinite, turbulent, and multi-dimensional, drives continuous methodological trends:

A. Shift Towards Facet Analysis and Synthesis

The major trend has been the transition away from purely enumerative classification (which lists all subjects readymade) toward analytico-synthetic classification.

• Faceted Schemes: Schemes like CC (Edition 4 onwards) are categorized as freely faceted schemes based on the flexible application of Ranganathan's Five Fundamental Categories (PMEST). This approach allows for the creation of unique, co-extensive class numbers for virtually infinite compound subjects.
• Adoption by Enumerative Schemes: Even historically enumerative schemes have absorbed faceted methodology. The DDC, originally enumerative, has increasingly relied on auxiliary tables (T1-T7) and 'divide like' devices to facilitate number building, thus becoming an "almost-enumerative classification" with synthetic features. The UDC is also recognized as a synthetic classification with a powerful auxiliary apparatus, making it a "truly multidimensional scheme".

B. Focus on Subject Specificity and Updating

The difficulty of assimilating new areas of interest quickly in classification schemes is a persistent challenge. Current trends address this through:

• Continuous Revision: Schemes like the DDC are revised more frequently than any other Universal Scheme. The UDC is also under continuous review to take account of new developments.
• Specific Subject Development: Research promotes the development of depth schedules and specialized classification systems to handle micro-documents and specific scientific disciplines more accurately than universal schemes.

III. Technological and Digital Trends

The emergence and overwhelming growth of digital libraries since the 1990s and the expansion of the Internet have catalyzed major technological trends in classification:

1. Role of Computers: The role of computers in classification theory is significant. Standardization in descriptive practices allows for the conversion of records to machine-readable form.
2. Computerization of Schemes: Major schemes are now available in electronic and web-based formats (e.g., Web Dewey). Computer programs based on facet analysis have been developed to construct class numbers and experiment with the use of CC in computerized document-finding systems.
3. Knowledge Organization (KO) for Retrieval: Classification is transforming into the broader field of Knowledge Organisation. UDC, for instance, is increasingly seen as suitable for micro documents, electronic information, and retrieval in online and networked databases and websites.
4. OPAC Integration: Classification schemes are now critical for Online Public Access Catalogues (OPACs). They allow for computer screen browsing and their hierarchical and synthetic notation is helpful in accurate retrieval. Class numbers can be used with logical operators (AND/OR/NOT) to broaden or narrow searches, thereby increasing the efficiency of information retrieval systems.
5. Web Organization and Subject Gateways: Library classification schemes are used to create cohesion across diverse information stores by linking conceptual contexts. Subject gateways (Web-based services that provide access to Internet resources) often use browse structures based on classification schemes like DDC. The use of classification schemes in web organization enhances browsing, improves recall and precision, and permits multilingual access.

IV. Organizational and Research Trends

Trends are also evident in the organizational structures supporting classification research:

• CRG (Classification Research Group): Formed in London in 1952, CRG has been influential in promoting faceted classification as the basis for information retrieval methods and has worked toward designing a general classification scheme suitable for computer retrieval (in association with the MARC Project).
• DRTC (Documentation Research and Training Centre): Established in Bangalore in 1962 by Ranganathan, DRTC actively promotes fundamental research to develop postulates and principles and development research to develop depth schedules.
• ISKO (International Society for Knowledge Organisation): Founded in 1989, ISKO organizes international conferences and promotes research focused on transforming library classification into Knowledge Organisation.

The increasing global cooperation, through bodies like FID/CR and ISKO, aims to unify standards and practices for the global sharing of information resources.