Guide to STN Patent Databases – Basic Version - Paton - TU Ilmenau

16 Search by subject
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Guide to STN Patent Databases
Subject searches are carried out in the main to establish the state of the art for a particular specialist field, to find out
about solutions to a technical problem, or to find patents comparable to a present invention (prior art). These
searches can take place with the aid of text entries (Text search) and of the International Patent Classification (IPC),
the National Classification (USCL in the USA), or the Derwent Classification (in DWPI) (Classification search). In some
databases it is possible to use special indexing entries for searching (Search by indexing).
Usually it is not possible to obtain a 100% complete list of text keywords (to search by text) or a 100% complete list
of classification codes, so a combined strategy is the best approach in many cases. Having a search problem
comprising two aspects, for example, both keywords and classification codes should be found for both aspects.
These will then be linked for the search using this scheme:
1. IPC* (Aspect 1) AND Keywords (Aspect 2)
2. Keywords (Aspect 1) AND IPC* (Aspect 2)
3. IPC* (Aspect 1) AND IPC (Aspect 2)
4. Keywords (Aspect 1) AND Keywords (Aspect 2)
(* or any other classification)
These four results will then be combined to form the total result (using the OR operator). Depending on the field of
search and the database used each partial search will yield a portion of the total result. This strategy is
demonstrated in the sample searches.
Moreover, the result of the plain text search (4th item) should be checked for the classification codes appearing in
the documents. Often this helps to improve the search strategy with respect to the classification.
16.1 Notes on subject searches in DWPI
In DWPI, in addition to the combined text and classification search a plain text search should always be made. By
the enhanced title and abstract by Derwent this database is ideal for a good result of plain text searches. Adverse
effects from an incorrect classification can be avoided this way.
It may also help to classify only to the level of the subclass and then combine these codes with a text search. The
Derwent Classification (DC) may also be used.
If abbreviations are used there is often a problem of the same abbreviation being used for different terms in
different specialist fields, e.g.:
ABS Acrylonitrile-Butadiene-Styrene Anti-Blocking System
GPS Glycoproteins Global Positioning System
PCB Polychlorinated Biphenyl Printed Circuit Board
Often it is enough to link the search query with the appropriate file segment or to exclude one file segment from
the search:
=> S GPS NOT CPI/FS
File segments in DWPI:
CPI Chemical Patent Index
EPI Electrical Patent Index
GMPI General and Mechanical Patent Index