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The volume of available information is immense and increasing, but it is not necessarily usable. The problem for an information-seeker is to find what is relevant and access what is needed - finding a way through the overwhelming volume of irrelevant material. There are various aids to doing this - some for virtual information (search engines for the Web) and some in either print or electronic form (bibliographies, catalogues, directories). They vary in effectiveness, and when relying on natural language can be limited by problems with words. (Did you use the right term? Are you searching in a single language? Are you missing relevant items in other languages?) Aside from sheer luck, search strategies are more effective if they can draw on information organized into patterns that correspond to the needs of most users - or are at least familiar to them - with related items brought together, and unrelated ones excluded - in other words, information that has been classified.
Even individual information collections for your own use need to be organized. Paper files will probably be kept in an order that reflects the way you normally use them. File management on a computer is a form of classification: it is simply a matter of grouping items according to their shared characteristics, e.g. the drive on which they are stored, the nature of the item (software, document, database etc) and its size, the project reference or other identifier, and the date. Multimedia items such as audio or video recordings, and collectable objects such as pictures, sculptures, coins or postage stamps are all sources of information, and their interest and informativeness is increased by systematic indexing. Even displays of retail goods, for example in a bookshop or in a supermarket, express the notion that the result of searching depends on the helpful arrangement of stock. Whatever form an item of information may take, logical organization is vital for the efficient use of the collection.
There are many types of information resources or documents: text, images (still and movinging), sound , datasets, events and objects and these are made available through different media i.e. recorded on different information carriers
- print media
- magnetically optically or electronically recorded information (DVD, CD-ROM, videotape etc)
- sound recordings
- Web pages
- objects in a collection (museum pieces, art objects, coins, stamps etc)
Any collection of them needs to be organized in such a way as to enable users to find what they want, while excluding irrelevant items. A classification scheme is a means of achieving this.
Some of the examples above are ways of physically grouping objects on shelves; by contrast, a directory on a computer groups not the files themselves, but identifiers or references from which you then go on to retrieve the item required - in other words, metadata. Classification schemes such as UDC can be used in either or both of these ways.
In some cases, the arrangement is decided locally (by the retailer, computer user etc); but the greater the quantity of items or their technical complexity becomes, the more helpful it is to follow a ready-made classification scheme, which represents a consensus as to a helpful order of classes.
Information can be organized by classifying it. Classification is a means of bringing order to a
multiplicity of concepts or items of information, by arranging them into classes - dividing the
universe of information (that is: all recorded knowledge) into manageable and logical portions.
A class is a group of concepts that have at least one thing in common. This shared property gives
the class its identity. Classifications may be designed for various purposes. They include:
- scientific classification
- classification for information indexing and retrieval
Scientific classifications arrange the phenomena of the natural world as an aid to systematic study.
They include the arrangements in systematic botany and zoology, and the table of chemical elements,
and they often form the basis of field guides. The other kind of classification is designed for
retrieval -in other words, locating the things you need. It includes documentary classifications -
that is: an aid to the management of documents, in order to make information locatable. The distinctions
are not watertight, and a documentary classification may incorporate scientific ones, as UDC does to
some extent in Chemistry, Botany and Zoology. A document is an information carrier - anything that
is a source of information, not necessarily verbal (it could be an image or an object).
Classes may consist of various kinds of concept, such as physical things (objects, persons,
places etc) and their parts, activities, processes, abstract ideas; for example:
- buildings (schools, churches, houses etc) - thin
- parts of buildings (doors, walls, stairways etc) - parts
- building services (joinery, glazing, plumbing etc) - activities
- architectural styles (classical, Georgian etc) - abstract ideas
A class may be further divided into smaller classes (or subclasses), and so on, until no further
subdivision is feasible. So classification is likely to be hierarchic, with each level of division
(except the lowest) divided into its logical subsets.
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Most classification schemes, including UDC, have a notation - a code that symbolizes the subject
of each class and its place in the sequence. A simple list of named classes, which would file
alphabetically, would not fulfil the purpose of keeping related things together, and separated
from unrelated things. This can be done by using a notation which has an inherent order, such
as numerals, alphabetic notation or a mixture (alphanumeric). When such a code is assigned to
each class, it expresses and fixes the filing order, and enables automatic sorting of entries.
Notation with variable length can also express the position in the hierarchy, with each extra
character representing a lower level; this is called expressive notation. Arabic numerals arranged
as decimal fractions are ideal for this purpose, and are the basis of the notation in UDC - as
its name implies. Decimal fractions also have the advantage of being infinitely extensible, so it
is always possible to introduce further subdivisions without altering the ordinal value of the rest
of the sequence. New developments, or increasingly detailed information, can therefore be
accommodated in the scheme by the creation of new classes while preserving the stability of
the rest. Such notation is said to be hospitable.
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Classification schemes may be either:
- special, that is: limited to a specific subject; or
- general, that is: aiming to cover all subjects equally ('the universe of information').
UDC is a general scheme. At the broadest level the structure of general classification schemes is based on disciplines which are recognized fundamental fields of study, such as Philosophy, Social sciences, Science, Technology, the Arts. Disciplines have their subdisciplines, e.g. sciences include Physics and Chemistry, and social sciences include Sociology and Economics. These areas of study are familiar because they tend to be represented in teaching departments, professional societies, specialized information services etc, and it can be useful for a classification scheme to follow this pattern.
The widely used general classification schemes are aspect classifications. A simple concept may have several places in the scheme, each representing a different aspect of it. For example, the simple concept 'horse' has aspects which are allowed for under Zoology, Animal husbandry, Transport, Sport and Recreation, among others. The subordination of simple concepts to fields of study reflects the normal expectations of people using information systems. A zoologist is less likely to be interested in items on horse racing than in items on the zoology of other equines.
Three most widely used general classification schemes are :
- Dewey Decimal Classification (DDC),
- Universal Decimal Classification (UDC).
- Library of Congress Classification (LCC), and
Though in all of them the arrangement of concepts is hierarchic ( 3.4), in LCC the hierarchy
is evident only from the position of a term on the printed page and not from the notation.
In DDC and UDC, the notation is expressive.
But UDC differs fundamentally from the others in that their main purpose is the arrangement of physical items (books etc) on shelves; in other words, they are designed to produce a single subject-based linear sequence of documents. By contrast, UDC was designed from the start for the organization of records of documents i.e. document surrogates or metadata - for the purpose of information retrieval.
A classification scheme is an indexing and retrieval language. It groups related items into classes, and arranges such groups in a hierarchy so that users can then trace topics in their context and scan subject field from general to specific or vice versa. :
- Subject organization in classification is not language-dependent, as the subject is symbolized by a class number, which allows for cross language and cross collection information discovery. Documents on a certain subject will be collocated under the same class number irrespective the language they are written in or the language of cataloguing centre assigning the UDC number, For instance, documents on nanotechnology in e.g. Chinese, German, French or British library will all be classed as 620.3 irrespective the language of the publication. lIt overcomes the ambiguities of natural language; for instance, the word 'paraffin' has both a technical sense (a series of saturated aliphatic hydrocarbons of the general formula CnH2n+2) and a popular one (=kerosine, a petroleum fraction with a particular boiling range), so a verbal search would retrieve many irrelevant results - but a class number is unambiguous. In UDC, paraffin production is at 665.637.2 and kerosine production is at 665.634.
- It can also help to overcome problems of unfamiliar terminology, allowing non-specialists to find information through subject browsing
- An internationally widely used scheme, such as UDC, can facilitate the exchange of information between systems, and provide a basic standard from which more specialized information retrieval tools may be developed.
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