Using Patent Citations to Enhance your Subject Searching
Search Tips - October 2000
Imagine the situation - you have done everything that you can to retrieve records in the Derwent World Patents Index (Derwent WPI) but you still have only a very small number of hits. You are sure that there must be other inventions which will be of interest to you - or perhaps you want to make absolutely certain there is nothing else. How about dipping into the Derwent Patents Citation Index (Derwent PCI), Derwent WPI's companion database, to find the patent citations associated with the records you have already found? This will automatically lead you to more information on the same - or closely related - topics.
What is a citation?
In the context of patents, a citation is a reference to a previous work which
is relevant to the current patent application. These citations are to be found
in the search reports which the patent office examiners produce when they check
that a particular invention really is new. And because it is the patent office
examiners who have made the connection between new ideas and existing ideas
we know that the connection must be valid - after all, the examiners are unbiased
and they are experts in their fields.
Citations can be existing patents of course - but they might also be non-patent publications such as journal articles, conference papers or trade literature. If you can find a list of citations associated with an invention you already know about then you have, in effect, found a good quality reading list.
What is in the Derwent PCI?
The top section of a Derwent PCI record looks almost exactly like
the top section of a Derwent WPI record - with the Derwent title,
the patent family, the patent assignee field and so on. However, lower down
- in place of an abstract - the Derwent PCI record lists the citations
associated with the patents in the family. (For clarity, we refer to this family
at the top of the record as the master family - it's the family
that the record is all about.)
A Derwent PCI record can contain both cited patents and literature and citing patents. It is very important to make a clear distinction between these.
Cited patents and literature = pre-existing technology, as listed in examiners' search reports. (Some inventor/applicant citations are covered too - where the applicants themselves have listed the existing technology which they know about.)
Citing patents = subsequent patent applications in whose search reports patents from the master family have appeared. In other words, these are later patent applications for inventions in a similar - or related - subject area.
If you can gather all the cited and citing patents associated with the inventions you already know about, you will immediately have access to a great deal more information on your subject. You will be making use of the work which the patent examiners have already done.
Many inventions are represented by a record in Derwent WPI (giving full subject classification and indexing, plus abstracts) and also by a record in Derwent PCI (listing citation data relating to the family members). Both database records will have the same Derwent title and they will both show the same patent family. Most importantly, both records will have the same Derwent accession number. This number can be thought of as a unique label for the invention (or the patent family) in the Derwent system. We will be using Derwent accession numbers to move between the two databases - Derwent WPI and Derwent PCI - in the search example below.
For full information on Derwent PCI's country and date coverage, see Derwent PCI INFORMATION.
Derwent PCI is available on Dialog (File 342) and STN (File Derwent PCI). It is not available on Questel.Orbit - instead, Questel.Orbit offers a handy citations display feature: simply add the word CITALL to the end of your normal display command and citation data from other databases will be brought in and displayed alongside your Derwent WPI records, eg LI MAXL CITALL. Full information on this command, and variations on it, is available from your local Questel.Orbit help desk. (And don't forget that a limited amount of citation data is also available in Derwent WPI.)
Why is citation searching so useful?
Because you are not dependent on words, and because citations can be of any
age and from any source, citation searching will often yield results that would
not have been obtained in a conventional subject search.
Records are retrieved because of the connection that the examiners have made - and this connection may not always be the "obvious" one. For example, you might be interested in electronic devices for counting banknotes; banknotes are simply a special type of sheet material so a citation search would yield, amongst other things, inventions relating to the counting of paper sheets into a photocopier.
Citation searching can also be very useful if your technology is one which has developed very rapidly over recent years. If you search using today's terminology you might not retrieve inventions from, say, five or ten years ago. This is because, if the technology if developing very rapidly, the terminology might also be changing - and a completely different vocabulary might have been used when the technology was in its infancy. Citation searching, being independent of words, overcomes this problem very easily.
Citation searching is also a useful method to use on those occasions when you are unsure of all the synonyms you should be incorporating into your search.
In addition to its role in enhancing subject searching, Derwent PCI is also an important source of competitor intelligence and business information. This way of using the database will be covered in a future search tip.
SEARCH EXAMPLES
STN:
Our subject is road cones - for traffic diversions on motorways, etc.
We start by gathering an accurate, reliable set of records in Derwent WPI. This will be the foundation of our search. It is very important to begin the process in Derwent WPI because this is the database that is designed for subject searching. Derwent WPI's abstracts make word searching very effective - a word search in Derwent PCI would give a much smaller result because abstracts are not present (only Derwent titles).
For the purposes of this example, we have used only a very simple word search. In the real world, the strategy would be much more comprehensive - perhaps involving synonyms, IPCs, Derwent Classifications and Derwent Manual Codes. STN's SET PLURALS command means that plurals (both regular and irregular) are searched automatically.
=> file wpindex
=> set plurals on
SET COMMAND COMPLETED
=> s road cone
62704 ROAD
9599 ROADS
66658 ROAD
(ROAD OR ROADS)
55945 CONE
10387 CONES
60091 CONE
(CONE OR CONES)
L1 48 ROAD CONE
(ROAD(W)CONE)
Using STN's SCAN format, we can take a look at a random selection of titles free-of-charge. This enables us to check for any major problems with false drops.
=> d scan
L1 48 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Transparent road cone - has upstanding conical portion with rectangular base and may contain coloured tint and cone may be hollow to facilitate stacking. HOW MANY MORE ANSWERS DO YOU WISH TO SCAN? (1):3 L1 48 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Road cones for use as lane restriction and off-limit signs - has multiple conical peripheral wall parts formed from top of conical shaped body which are pressed and inserted into base, to press against inner periphery after releasing. L1 48 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI See-through road cone - has upper and lower rings with top defining viewing apertures and sidewall spaced by viewing gaps carrying sign. L1 48 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Road cone for traffic safety - has main body with retro-reflective material with ridged stacking protector for material held in lip and recess. HOW MANY MORE ANSWERS DO YOU WISH TO SCAN? (1):0 |
Each of these 48 Derwent WPI records contains the details of one or more patent applications and many of these will have been checked for novelty by patent examiners. The examiners will have noted any prior art in their search reports and the cited documents will be listed in corresponding Derwent PCI records (provided the country and date of the application in question are within the coverage of the database). If we can find the details of these citations - and perhaps also the later citing patents - we will have instantly extended the scope of our search.
The first step is to retrieve the appropriate Derwent PCI records.
The 48 Derwent WPI records above are all labelled with their own Derwent accession number (AN). The matching records in Derwent PCI will be labelled with the same number - so we can make use of this to retrieve them. (Patent numbers could also be used, but since each record may contain the details of more than one patent this is a far less elegant way of carrying out the search.)
STN's TRANSFER command enables us to do this very speedily.
First, we go to our destination - Derwent PCI. Then we reach back into Derwent WPI and collect the data that we need - the Derwent accession numbers (AN) of all the records (1-) in L1. STN then automatically searches for these in Derwent PCI.
=> file dpci
=> transfer l1 1- an
L2 TRANSFER L1 1- AN : 48 TERMS
L3 35 L2
The result obtained in L3 shows us that 35 of the original 48 inventions are represented in Derwent PCI. Each of these 35 Derwent PCI records will contain lists of cited and citing patents - our readymade reading lists. The numbers of the cited and citing patents will of course be given - and if the patent is also represented in Derwent WPI, the Derwent accession number of the appropriate record will be listed alongside. As in the previous step, this gives us a very neat link between the databases. (Of course some of the older cited patents may pre-date Derwent WPI and there may also be some that are outside its country coverage. These represent additional valuable information but will need to be sourced elsewhere.)
If you have not used Derwent PCI before, it will help you to know that most search and display fields are labelled in the same way as in a Derwent WPI record - PN, PA, etc. In the master family, the labels are exactly the same; lower down the record, ".D" is used to distinguish information about cited patents (eg PN.D); and ".G" is used to distinguish information about citing patents (eg PN.G). The one exception to this is the Derwent accession numbers of the cited and citing patents. The qualifier "OS" is used - meaning "other source" (ie Derwent WPI rather than Derwent PCI). OS.D is the field label for the accession numbers of the cited patents; OS.G is the field label for the accession numbers of the citing patents. (See Yellowsheet for full details of all search and display fields.)
All we need to do now is take all the citation data back into Derwent WPI so that we can look at detailed information about the inventions (Derwent titles, abstracts, patent families, etc). We do not need to look at any records in Derwent PCI - STN's TRANSFER command will "memorise" all the data for us and search for it automatically.
As in the previous step, we go to our destination first - Derwent WPI in this case. Then we reach back into Derwent PCI and collect the data that we need - the Derwent accession numbers of the cited and citing patents (OS.D, OS.G), as listed in the all the Derwent PCI records (1-) in L3. The Derwent accession numbers harvested from the Derwent PCI records are of course labelled OS.D and OS.G; we need to re-label them AN in order for them to be understood by Derwent WPI.
=> file wpindex
=> transfer l3 1- os.d os.g /an
L4 TRANSFER L3 1- OS.D OS.G : 119 TERMS L5 118 L4/AN
The result is 118 Derwent WPI records. These are the Derwent WPI records for all the cited and citing patents associated with our original 48 inventions.
The final step is to eliminate any that we have already seen - ie those records containing the term "road cone" - then take a look at a selection of titles.
=> s l5 not l1 L6 106 L5 NOT L1
=> d scan
L6 106 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Vehicle-borne device for positioning traffic control cones - releases each cone in turn from base of inclined stack by manual or automatic conveyor switching. HOW MANY MORE ANSWERS DO YOU WISH TO SCAN? (1):3 L6 106 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Retroreflective traffic bollard - has sheet of retroreflective material disposed in recess between projections on exterior surface which is/are located or dimensioned to protect against impact. L6 106 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Conveyor for automatically distributing and collecting traffic cones - comprises frame fitted with conveyor belt, driving wheels and scoop. L6 106 WPINDEX COPYRIGHT 2002 Derwent INFORMATION LTD TI Device for standing dominoes in line on table - has notched wheel taking pieces from housing and rotating them to vertical position before deposition. HOW MANY MORE ANSWERS DO YOU WISH TO SCAN? (1):0 => logoff y |
Our final result is 106. Note that we have not had to use any extra words to find these records - we have simply been using Derwent accession numbers and the links that have already been provided by the patent examiners. Glancing through the sample of titles above, we can see that many of these 106 records would not have been retrieved in an ordinary subject search - either because of the different terminology (eg "bollard") or because of the indirect link between technologies that the examiners have been able to spot (eg the device for standing dominoes in line on a table; scaled up, the same kind of device could be used for setting out an even line of cones along a road).
To summarise:
We began by retrieving a good set of records in Derwent WPI. Then we
dipped into Derwent PCI to find the citations associated with these inventions.
We finished by taking these citations back to Derwent WPI so that we
could read their titles and abstracts.
DIALOG:
Our subject is road cones - for traffic diversions on motorways, etc.
We start by gathering an accurate, reliable set of records in Derwent WPI. This will be the foundation of our search. It is very important to begin the process in Derwent WPI because this is the database that is designed for subject searching. Derwent WPI's abstracts make word searching very effective - a word search in Derwent PCI would give a much smaller result because abstracts are not present (only Derwent titles).
For the purposes of this example, we have used only a very simple word search. In the real world, the strategy would be much more comprehensive - perhaps involving synonyms, IPCs, Derwent Classifications and Derwent Manual Codes.
? b 351
? s road()cone?
62211 ROAD 61420 CONE? S1 48 ROAD()CONE?
Using the low-cost Format 26, we can take a look at a few titles. This enables us to check for any major problems with false drops.
? t 1/26/1-3
1/26/1 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 013037849 **Image available** WPI Acc No: 2000-209701/200019 Inflatable road cone for traffic regulation during road construction, accident - is made of flexible sheet which is expanded to cone shape by air pressure or by coil spring 1/26/2 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 011954438 **Image available** WPI Acc No: 1998-371348/199832 Road cones for use as lane restriction and off-limit signs - has multiple conical peripheral wall parts formed from top of conical shaped body which are pressed and inserted into base, to press against inner periphery after releasing 1/26/3 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 011011259 **Image available** WPI Acc No: 1996-508209/199651 Device for collection and deployment of road cones - has ramp possessing endless belt driven by steerable rolling support member, with belt driven at same speed as device travelling along road |
Each of these 48 Derwent WPI records contains the details of one or more patent applications and many of these will have been checked for novelty by patent examiners. The examiners will have noted any prior art in their search reports and the cited documents will be listed in corresponding Derwent PCI records (provided the country and date of the application in question are within the coverage of the database). If we can find the details of these citations - and perhaps also the later citing patents - we will have instantly extended the scope of our search.
The first step is to retrieve the appropriate Derwent PCI records.
The 48 Derwent WPI records above are all labelled with their own Derwent accession number (AX). The matching records in Derwent PCI will be labelled with the same number - so we can make use of this to retrieve them. (Patent numbers could also be used, but since each record may contain the details of more than one patent this is a far less elegant way of carrying out the search.)
Dialog's MAP command enables us to do this very speedily - extracting all the accession numbers from the Derwent WPI records and creating an "invisible" saved strategy for re-searching them. By including "t" in the MAP command, we ensure that this saved strategy is only temporary; it will disappear after we logoff so there will be no fee to pay.
? map ax t
Processing MAP
9 Select Statement(s), 92 Search Term(s)
Serial#TD285
We now go to Derwent PCI and execute the strategy. Since we are using it straight away, without saving anything else in the interim, there is no need to make a note of the saved strategy serial number; EXS on its own is sufficient.
? b 342
? exs
Executing TD285
1 AX=1978-42606A
1 AX=1980-G8765C
0 AX=1980-H6991C
0 AX=1981-A6158D
1 AX=1982-H9955E
0 AX=1984-208922
1 AX=1985-148234
1 AX=1985-192250
1 AX=1985-251535
0 AX=1986-227412
1 AX=1987-137909
1 AX=1988-149629
1 AX=1988-185134
S1 9 AX=1978-42606A + AX=1980-G8765C + AX=1980-H6991C +
AX=1981-A6158D + AX=1982-H9955E + AX=1984-208922 +
AX=1985-148234 + AX=1985-192250 + AX=1985-251535 +
AX=1986-227412 + AX=1987-137909 + AX=1988-149629 +
AX=1988-185134
.
.
.
.
S9 35 S1:S8
The result obtained in S9 shows us that 35 of the original 48 inventions are represented in Derwent PCI (system responses have been shortened for reasons of space). Each of these 35 Derwent PCI records will contain lists of cited and citing patents - our readymade reading lists. The numbers of the cited and citing patents will of course be given - and if the patent is also represented in Derwent WPI, the Derwent accession number of the appropriate record will be listed alongside. As in the previous step, this gives us a very neat link between the databases. (Of course some of the older cited patents may pre-date Derwent WPI and there may also be some that are outside its country coverage. These represent additional valuable information but will need to be sourced elsewhere.)
If you have not used Derwent PCI before, it will help you to know that the field labels in the master family are the same as those in a Derwent WPI record - PN, PA, etc. Many of the same qualifiers are also used in the citation fields - with the addition of CT to distinguish cited patents and CG to distinguish citing patents (see Bluesheet for full details). The codes for the Derwent accession numbers of the cited and citing patents are RXCT and RXCG respectively - "RX" being used in place of "AX" to highlight the fact that these are the accession numbers of citations (think citations¿. think bibliographic references - the principles are similar).
All we need to do now is take all the citation data back into Derwent WPI so that we can look at detailed information about the inventions (Derwent titles, abstracts, patent families, etc). We do not need to look at any records in Derwent PCI - Dialog's MAP command will "memorise" all the data for us and search for it automatically. Remember that the Derwent accession numbers harvested from the Derwent PCI records will be labelled RXCT and RXCG; we need to re-label them AX in order for them to be understood by Derwent WPI.
? map rxct t /ax=
Processing MAP
5 Select Statement(s), 60 Search Term(s)
Serial#TD286
? map rxcg t /ax=
5 Select Statement(s), 57 Search Term(s)
Serial#TD287
Because MAP can only extract data from one field at a time, we need to perform two MAPs - one for the cited patents (RXCT) and one for the citing patents (RXCG). Separate saved search strategies are created and each of these must be separately executed in Derwent WPI. The results are then combined using OR. (System responses have been shortened for reasons of space.)
? b 351
? exs td286
1 AX=68-44040Q
1 AX=68-68247P
1 AX=68-79127P
1 AX=74-B5327V
1 AX=77-H6953Y
1 AX=77-J2562Y
.
.
.
.
S5 60 S1:S4
? exs td287
1 AX=00-039855
1 AX=00-126193
1 AX=00-170546
1 AX=00-317105
1 AX=81-53249D
1 AX=86-291622
.
.
.
.
S10 59 S6:S9
? s s5 or s10
60 S5
59 S10
S11 118 S5 OR S10
The result is 118 Derwent WPI records. These are the Derwent WPI records for all the cited and citing patents associated with our original 48 inventions.
The final step is to eliminate any that we have already seen - ie those records containing the term "road cone" - then take a look at a selection of titles.
? s s11 not road()cone?
118 S11
62211 ROAD
61420 CONE?
48 ROAD(W)CONE?
S12 106 S11 NOT ROAD()CONE?
? t 12/26/1-5
12/26/1 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 013351906 **Image available** WPI Acc No: 2000-523845/200047 Traffic safety cone for marking e.g. construction zone, has two flexible panels which are attached to outer surface of conical body to allow reception of another conical body within cavity 12/26/2 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 008599449 **Image available** WPI Acc No: 1991-103481/199115 Vehicle-borne device for positioning traffic control cones - releases each cone in turn from base of inclined stack by manual or automatic conveyor switching 12/26/3 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 008345331 **Image available** WPI Acc No: 1990-232332/199031 Traffic cone for use on motorways - is wedge- shaped with curved sided tapering narrow sides and stands on fixed base 12/26/4 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 007423654 **Image available** WPI Acc No: 1988-057589/198809 Base for traffic bollard - has rectangular panel with slot to receive stem of upright marker cone 12/26/5 DIALOG(R)File 351:Derwent WPI (c) 2002 Derwent Info Ltd. All rts. reserv. 002323127 WPI Acc No: 1980-C9561C/198013 Device for standing dominoes in line on table - has notched wheel taking pieces from housing and rotating them to vertical position before deposition ? logoff |
Our final result is 106. Note that we have not had to use any extra words to find these records - we have simply been using Derwent accession numbers and the links that have already been provided by the patent examiners. Glancing through the sample of titles above, we can see that many of these 106 records would not have been retrieved in an ordinary subject search - either because of the different terminology (eg "bollard") or because of the indirect link between technologies that the examiners have been able to spot (eg the device for standing dominoes in line on a table; scaled up, the same kind of device could be used for setting out an even line of cones along a road).
To summarise:
We began by retrieving a good set of records in Derwent WPI. Then we
dipped into Derwent PCI to find the citations associated with these inventions.
We finished by taking these citations back to Derwent WPI so that we
could read their titles and abstracts.
For further assistance please contact your local Derwent Help Desk.