Page "Dewey Decimal Classification" Paragraph 37

Another disadvantage of DDC is that it was developed in the 19th century essentially by one man and was built on a top-down approach to classify all human knowledge, which makes it difficult to adapt to changing fields of knowledge.

The Library of Congress Classification system was developed based mainly on the idea of literary warrant ; classes were added ( by individual experts in each area ) only when needed for works owned by the Library of Congress.

As a result, while the Library of Congress Classification system was able to incorporate changes and additions of new branches of knowledge, particularly in the fields of engineering and computer science ( the greater hospitability of the Library of Congress Classification was also a factor ), DDC has been criticized for being inadequate in covering those areas.

It is asserted that, as a result, most major academic libraries in the US do not use the DDC because the classification of works in those areas is not specific enough, although there are other reasons that may truly be more weighty, such as the much lower expense of using a unique " pre-packaged " catalog number instead of having highly skilled staff members engaging in the time-consuming development of catalog numbers.