Ordinal Numbers:

These are used not for the purpose of counting but ordering and mechanising the arrangement of things. For example, participants in a conference can be listed in a desired sequence on the basis of some suitable principle and then this sequence can be mechanised with the help of ordinal numbers. Melvil Dewey  (1851-1931) ,  the  father  of  modern  library classification, was the first classificationist to use simple Indo-Arabic numerals (0-9) as ordinal numbers for the systematiclisting of subjects both broader and narrower, in his Decimal Classification first published in 1876 (see Unit 4, Unit 10 and Unit 11 of this Course and Blocks I and 2 of BLJ&03P to know  more about Dewey Decimal Classification). Since then the system of ordinal numbers-notation as it is called in library classification-has been the principal element in the design and use of library classification schemes. 

Specific Subject : The contents of a document may deal with some field of knowledge. It is a prerequisite for a classifier to know what subject matter the document exactly contains. After ascertaining the exact subject, or specific subject, the classifier translates that specific subject into the artificial language or ordinal numbers of the classification scheme used. In order to know the specific subject of the document the classifier has to examine its title, contents page, preface and introduction, and to scan through some chapters, and, if necessary to go through the entire book.

There may be certain occasions where a classifier has to consult an expert to ascertain the specific subject of a document. Ranganathan defines the specific subject of a document as "that division of knowledge whose extension and intension are equal to those of its thought content". Extension means the scope (if the subject treatment and intension means the depth of the subject treatment in a given document. Palmer and Wells define it as "that division of knowledge which exactly comprehends all the major factors that go in its making".