A brief account of the NASA Thesaurus is presented. Some typical problems encounted in information search using the subject indexes to the Scientific and Technical Aerospace REports (STAR) and International Aerospace Abstracts which are compiled using NASA Thesaurus, are mentioned. Use of facet analysis and synthesis based on S R Ranganathan's subject structure model is recommended for use along with the thesaurus to secure precise and consistent search formulation for compound subjects

Anjaneyulu, V.

English

Librarians' Digital Library

SEMINAR ON THESAURUS (1975). P a p e r CC 
NASA THESAURUS IN INFORMATION RETRIEVAL 
V ANJANEYULU, L i b r a r y , V i k r a m S a r a b h a i Space C e n t r e , T r i v a n d r u m , K e r a l a 
A br ief account of the NASA T h e s a u r u s is p r e s e n t e d . Some typi -
cal p r o b l e m s encounted in in format ion s e a r c h us ing the subjec t indexes to 
the Scient i f ic and Techn ica l A e r o s p a c e Repo r t s (STAR) and In te rna t iona l 
A e r o s p a c e A b s t r a c t s which a r e compi led using NASA T h e s a u r u s , a r e m e n -
t ioned. Use of facet a n a l y s i s and syn thes i s based on S R Rangana than ' s 
sub jec t s t r u c t u r e model is r e c o m m e n d e d for use along with the t h e s a u r u s 
to s e c u r e p r e c i s e and cons i s t en t s e a r c h fo rmula t ion for compound s u b j e c t s . 
1 S C O P E OF THE P A P E R 
Th i s pape r p r e s e n t s a br ief account of 
the NASA T h e s a u r u s and i l l u s t r a t e s wi th a few 
e x a m p l e s p r o b l e m s encoun te r ed in the use of 
t h e s a u r u s in in format ion r e t r i e v a l . The need 
for guidel ines for combining facets and o ther 
component ideas of a sub jec t is pointed out. 
S R Rangana than ' s p r i n c i p l e s for face t syntax 
a r e r e c o m m e n d e d for use in in format ion r e -
t r i e v a l . 
2 NASA THESAURUS 
21 The Ed i t i ons 
The f i r s t p r e l i m i n a r y edi t ion of the 
NASA T h e s a u r u s was publ ished in 1967 in 3 
v o l u m e s . The f i r s t two vo lumes conta ins the 
a lphabe t ica l p a r t and the th i rd volume conta ins 
four a p p e n d i c e s . The appendices p r e s e n t a 
h i e r a r c h i c a l d i sp l ay of the d e s c r i p t o r s , c a t ego ry 
t e r m l i s t , p e r m u t e d index, and pos tab le t e r m 
index. The h i e r a r c h i c a l d i sp lay l i s t s a l l the 
subjec t t e r m s that m e e t the following c r i t e r i a : 
1 Subject t e r m s having no b r o a d e r r e f e r -
ence ; and 
2 At l e a s t two leve l s of spec i f ic i ty a r e 
conta ined in the N a r r o w e r T e r m (NT). 
The c a t e g o r y t e r m l i s t contains an a lpha-
be t i c a l l i s t ing of subject t e r m s under e a c h of the 
subjec t c a t e g o r i e s . The f i r s t two digi ts in the 
four digit c a t e g o r y code denote the s u b - c a t e g o r y 
The p e r m u t e d index i s an a lphabe t ica l a r r a n g e -
ment of e v e r y k e y word o c c u r r i n g in the pos table 
t e r m s , cons i s t ing of m o r e than one word . The 
pos tab le t e r m index c o n s i s t s of an a lphabe t ica l 
l i s t ing of a l l subject t e r m s val id for indexing. 
USE r e f e r e n c e s a r e not included. 
The updated edi t ion was publ ished in 
1972 and contains 14, 002 pos tab le t e r m s . The 
subjec t f ields c o v e r e d a r e l i s t ed in the Appen-
dix (Sec 6). The NASA T h e s a u r u s is designed 
to i n c o r p o r a t e all the s a l i en t f e a t u r e s of a the-
s a u r u s . I t l i s t s the d e s c r i p t o r s alphabetically, 
p rov ides for the cont ro l of synonyms and homo-
nyms , and d i sp l ays g e n e r i c - s p e c i f i c and other 
a s s o c i a t i v e r e l a t i ons among concepts (BT, NT, 
R T ) . A c r o n y m s and abb rev ia t ions a r e widely 
used in the a e r o s p a c e field. T h e s e a re used as 
p r e f e r r e d t e r m s with c r o s s r e f e r e n c e from the 
full f o r m . NASA r e s t r i c t s the length of a des-
c r i p t o r to 42 c h a r a c t e r s . The m a i n objective 
of the NASA T h e s a u r u s is to m e e t the institu-
t ional needs of in fo rmat ion s t o r age and retrie-
val in the a e r o s p a c e field. Its subject-fields 
cover m a i n l y the r e s e a r c h and development 
ac t iv i t i e s of NASA. 
3 COVERAGE OF NASA THESAURUS 
AND TEST 
L a u r a Ra iney (12) has compared the sub-
j e c t c o v e r a g e be tween the NASA Thesaurus and 
TEST. Using the c r i t e r i o n that a 50% coverage 
of documen t s could const i tu te effective coverage 
of a d i sc ip l ine , the following subjects were found 
to be effect ively c o v e r e d by NASA Thesaurus: 
A e r o n a u t i c s 
A e r o d y n a m i c s 
A s t r o n o m y and A s t r o p h y s i c s 
Communica t i on 
E a r t h Sc ience 
E l e c t r o n i c s and E l e c t r i c a l Equipment 
E n g i n e e r i n g 
Me teo ro logy 
M i s s i l e Technology 
P r o p e l l a n t and P r o p u l s i o n 
Space Technology 
F u r t h e r , NASA has b e t t e r coverage of Aero-
naut ics and A e r o d y n a m i c s , while TEST has 
C 20 
NASA thesaurus CC46 
better coverage of Engineering. Thesauri 
built for different institutional uses may not be 
compatible with each other. Hence, the design 
of thesauri for wider use should be based on the 
structure of subjects rather than just to meet 
institutional needs. Each institution may have 
to cover certain core disciples fully and some-
what superficially peripheral disciplines. 
NASA's coverage is satisfactory for its core 
disciplines and less so for pheripheral disci-
plines. 
PROBLEMS IN RETRIEVAL 
Hum is used for rocket nose cone and/or other 
parts, using the term alone was not helpful. 
Search under 'solid propellant' was too generic, 
since all types of propellants are listed. Hier-
archial relations built in the indexing language 
could help in directing the search from generic 
to specific: Example 
Propellant 
Solid Propellant 
Beryllium 
Hierarchial relation provides the context for the 
term used. 
NASA Thesaurus is used as an informa-
tion retrieval tool for manual search in the 
Vikram Sarahhai Space Centre. The informa-
tion sources used are the annual subject indexes 
of Scientific and Technical Aerospace Reports 
{STAR) and International Aerospace Abstracts 
which are prepared using the NASA Thesaurus. 
Numerous searches have been made in response 
to the questions of users during the last three 
years. A few typical problems encountered 
using these tools are mentioned below. In 
some cases interaction with users improved the 
retrieval performance. 
44 Problem Type 4 
Query : Information on : Reliability of 
electronic components used in 
digital computers. 
Search under 'digital computer' was too 
generic. From the descriptor 'Reliability1 the 
thesaurus directs to the NT 'component reliabi-
lity. Under 'component reliability' all types 
of components were found listed However, 
search was continued until document index terms 
matching the descriptor could he picked up. 
41 Problem Type 1 4S Problem Type 5 
Search under a single facet creates 
ambiguity because single facet has no syntax 
and the search is too generic. 
4Z Problem Type 2 
Search under two or more facets which 
are pre coordinated improved the retrieval re-
sults. The question to what extent the precoordi-
nation can be made between terms remains un-
answered. Also, there are no guidelines for 
precoordination of terms. For example : 
Rocket Engine Design 
Rocket Fuel Tank 
Rocket Launching 
Whole-Part-Action 
Whole-Part 
Whole-Action 
A retrospective search was made under 
'solid propellant binder'. It was found that the 
earlier subject indexes used the terms 'propel-
lant binder' but later indexes use 'solid propel-
lant binder'. Change in descriptors effects re-
trospective search. While change of termino-
logy would be necessary to conform to current 
usage, it would help retrospective searches if a 
list of the changes with date is given especially 
when the changes are frequent and new and up-
dated editions of the thesaurus are published. 
46 Problem Type 6 
Query : Information on aging effects of 
solid propellant rocket motors 
Fibre Glass Rein- Solid Propellant 
forced Plastics Rocket Motor Case 
Pre coordinated 
43 Problem Type 3 
Precoordinated 
Query : Information on : Beryllium 
used as propellant. 
In the thesaurus the descriptor 'Beryl-
lium' is not subdivided by "use". Since Beryl-
First the search was made under the 
descriptor 'aging'. Although the term is given 
in the subject index, it is used as Aging (Ma-
terial), Aging(Biology) . The search was made 
under the descriptor 'solid propellant rocket 
motor'. As the user 's query did not match with 
the documents identified, the user was requested 
to reformulate his query. The modified query 
was "Performance of solid propellant rocket 
motor after prolonged storage". Search was 
made again under the descriptor 'solid propel-
lant rocket motor' and some 4 references were 
C Zl 
CC46 ANJANEYULU 
found for the modif ied q u e r y . Th i s type of 
s e a r c h i n g with in t e rac t ion with the u s e r helps 
to i m p r o v e the s e a r c h s t r a t e g y . 
47 P r o b l e m Type 7 
Q u e r y : In format ion on : Des ign and 
i n s t a l l a t i on of side looking 
r a d a r in the sa t e l l i t e for 
r e m o t e sens ing of e a r t h 
r e s o u r c e s . 
P o s t a b l e T e r m s 
1 Remote s e n s o r 
2 E a r t h r e s o u r c e s 
3 Side looking r a d a r 
4 Sate l l i te borne r a d a r 
(Design and ins ta l la t ion) 
F i r s t , s e a r c h was made under the d e s -
c r i p t o r s ' r e m o t e s e n s o r s ' and ' e a r t h r e s o u r -
c e s ' . As t h e r e w e r e too m a n y documents l i s t ed 
under these d e s c r i p t o r s i t was difficult to pin-
point r e l evan t d o c u m e n t s . S e a r c h was then made 
under ' R a d a r ' which d i r e c t s to NTs such as 
' s i d e looking r a d a r ' and ' s a t e l l i t e borne r a d a r ' . 
As the n u m b e r of documen t s w e r e fewer under 
these d e s c r i p t o r s the range of s e a r c h was 
r e d u c e d and i t was poss ib le to locate the r e l e -
vant document . 
The document was l i s t e d under a l l the 4 
d e s c r i p t o r s , thus i n c r e a s i n g indexing cos t and 
s e a r c h t i m e . B e s i d e s , if t hese 4 d e s c r i p t o r s 
were to be p e r m u t e d then the number of e n t r i e s 
i n c r e a s e s to 24 e n t r i e s . If t h e r e is no s e m a n t i c 
con t ro l over these concepts , s e a r c h b e c o m e s 
t ed ious . 
48 P r o b l e m Type 8 
Q u e r y : In format ion on : N o n - d e s t r u c -
tive t e s t ing of sol id rocke t 
m o t o r s used in scout launch 
veh ic le . 
S e a r c h had to be made under each facet 
and scan manua l ly all the documents indexed 
under each d e s c r i p t o r and se lec t the r e l evan t 
d o c u m e n t s . In the a e r o s p a c e field such e x a m -
ples a r e quite common. 
5 SEARCH STRATEGY 
L a n c a s t e r (6) points out that exhaus t i -
vity and spec i f ic i ty m a y be appl ied to s e a r c h i n g 
as wel l as to indexing. L a u r a Ra iney (12) 
a t t r i bu t ed the s e a r c h fa i lure with NASA Thesau -
r u s to the following fac to r s : 
1 S e a r c h formula t ion not specif ic 
2 S e a r c h fo rmula t ion not exhaus t ive 
3 S e a r c h used i n a p p r o p r i a t e t e r m s or 
t e r m combina t ions 
4 Defect in s e a r c h logic 
The t h e s a u r u s fac i l i t a tes v o c a b u l a r y 
con t ro l and fo rmula t ion of s e a r c h s t r a t e g y to a 
l imi t ed extent . I t he lps the cons i s t en t choice 
of s t a n d a r d t e r m s , r e s o l v e p r o b l e m s due to 
synonyms and homonyms , v a r i a t i o n s in the 
spel l ing of words e t c . , and to obtain b r o a d e r , 
n a r r o w e r t e r m s , and r e l a t e d t e r m s for a given 
d e s c r i p t o r o c c u r r i n g in a r e a d e r ' s query . How-
e v e r , often to specify coex tens ive ly the subject 
of a que ry it would be n e c e s s a r y to p r e c o o r d i -
nate the d e s c r i p t o r s . To do this in a consistant 
way gu ide - l ines a r e n e c e s s a r y . In a manual ly 
indexed s y s t e m using m u l t i w o r d e d subjec t head-
ings / index ing t e r m s , the syntax of the s e a r c h 
fo rmula t ion should m a t c h t h e syntax of the sub-
j ec t h e a d i n g s / i n d e x i n g t e r m s used . This implies 
the use of the s a m e se t of gu ide l ines in the for-
mula t ion of subject head ings / index ing t e r m s as 
well as the s e a r c h d e s c r i p t o r combina t ions . 
F a c e t ana lys i s and syn thes i s technique 
p a r t i c u l a r l y that baaed on a se t of exp l ic i t ly 
s ta ted guiding p r i n c i p l e s and a sound t h e o r y of 
subject s t r u c t u r e and c l a s s i f i ca t ion could be of 
c o n s i d e r a b l e he lp in the deve lopment of thesauri , 
the s t r u c t u r i n g of subjec ts of documents and 
fo rmu la t i on of subject headings / index ing t e r m s 
and in the p re coord ina t ion of d e s c r i p t o r s in the 
fo rmu la t i on of s e a r c h s t r a t e g y . S R Ranga -
na than ' s model (10-11) of subjec t s t r u c t u r i n g 
has been found helpful in our actual p r a c t i c e of 
in format ion s e a r c h and the re fo re could be used 
in combinat ion with the t h e s a u r u s in obtaining 
m o r e s a t i s f a c t o r y s e a r c h r e s u l t s . 
6 APPENDDC 
61 NASA Old Subject C a t e g o r i e s 
Subject C a t e g o r i e s 
01 
02 
03 
04 
05 
06 
07 
08 
09 
10 
11 
12 
A e r o d y n a m i c s 
A i r c r a f t 
Aux i l i a ry Sys t ems 
B i o s c i e n c e s 
Biotechnology 
C h e m i s t r y 
Communica t ions 
C o m p u t e r s 
E l e c t r o n i c Equ ipment 
E l e c t r o n i c s 
F a c i l i t i e s , R e s e a r c h and Support 
F lu id Mechan ic s 
C 22 
NASA t h e s a u r u s CC62 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
G e o p h y s i c s 
I n s t r u m e n t a t i o n a n d P h o t o g r a p h y 
M a c h i n e E l e m e n t s a n d P r o c e s s e s 
M a s e r s 
M a t e r i a l s , M e t a l l i c 
M a t e r i a l s , N o n m e t a l l i c 
M a t h e m a t i c s 
M e t e o r o l o g y 
N a v i g a t i o n 
N u c l e a r E n g i n e e r i n g 
P h y s i c s , G e n e r a l 
P h y s i c s , A t o m i c , M o l e c u l a r a n d 
N u c l e a r 
P h y s i c s , P l a s m a 
P h y s i c s , S o l i d - S t a t e 
P r o p e l l a n t s 
P r o p u l s i o n S y s t e m s 
S p a c e R a d i a t i o n 
S p a c e S c i e n c e 
S p a c e V e h i c l e s 
S t r u c t u r a l M e c h a n i c s 
T h e r m o d y n a m i c s a n d C o m b u s t i o n 
G e n e r a l 
24 
25 
26 
27 
28 
ENG 
31 
32 
33 
34 
35 
36 
37 
38 
39 
GE 
42 
4 3 
44 
6 2 N A S A N e w S u b j e c t C a t e g o r i e s 
Sub jec t C a t e g o r i e s 
A E R O N A U T I C S 
C o m p o s i t e M a t e r i a l s 
I n o r g a n i c a n d P h y s i c a l C h e m i s t r y 
M e t a l l i c M a t e r i a l s 
N o n m e t a l l i c M a t e r i a l s 
P r o p e l l a n t s a n d F u e l s 
G I N E E R I N G 
E n g i n e e r i n g ( G e n e r a l ) 
C o m m u n i c a t i o n s 
E l e c t r o n i c s a n d E l e c t r i c a l E n g i n e e r i n g 
F l u i d M e c h a n i c s a n d H e a t T r a n s f e r 
I n s t r u m e n t a t i o n a n d P h o t o g r a p h y 
L a s e r s a n d M a s e r s 
M e c h a n i c a l E n g i n e e r i n g 
Q u a l i t y A s s u r a n c e a n d R e l i a b i l i t y 
S t r u c t u r a l M e c h a n i c s 
O S C I E N C E S 
G e o s c i e n c e s ( G e n e r a l ) 
E a r t h R e s o u r c e s 
E n e r g y P r o d u c t i o n a n d C o n v e r s i o n 
4 5 E n v i r o n m e n t P o l l u t i o n 
4 6 G e o p h y s i c s 
4 7 M e t e o r o l o g y a n d C l i m a t o l o g y 
4 8 O c e a n o g r a p h y 
L I F E S C I E N C E S 
01 A e r o n a u t i c s ( G e n e r a l ) 
02 A e r o d y n a m i c s 
0 3 A i r T r a n s p o r t a t i o n a n d S a f e t y 
0 4 A i r c r a f t C o m m u n i c a t i o n s a n d 
N a v i g a t i o n 
0 5 A i r c r a f t D e s i g n 
T e s t i n g a n d P e r f o r m a n c e 
0 6 A i r c r a f t I n s t r u m e n t a t i o n 
0 7 A i r c r a f t P r o p u l s i o n a n d P o w e r 
0 8 A i r c r a f t S t a b i l i t y a n d C o n t r o l 
0 9 R e s e a r c h a n d S u p p o r t F a c i l i t i e s ( A i r ) 
A S T R O N A U T I C S 
12 A s t r o n a u t i c s ( G e n e r a l ) 
13 A s t r o d y n a m i c s 
1 4 G r o u n d S u p p o r t S y s t e m s a n d F a c i l i t i e s 
( S p a c e ) 
1 5 L a u n c h V e h i c l e s a n d S p a c e V e h i c l e s 
16 S p a c e T r a n s p o r t a t i o n 
1 7 S p a c e c r a f t C o m m u n i c a t i o n s . C o m m a n d 
a n d T r a c k i n g 
18 S p a c e c r a f t D e s i g n . T e s t i n g a n d 
P e r f o r m a n c e 
19 S p a c e c r a f t I n s t r u m e n t a t i o n 
2 0 S p a c e c r a f t P r o p u l s i o n a n d P o w e r 
CHEMISTRY A N D M A T E R I A L S 
23 C h e m i s t r y a n d M a t e r i a l s ( G e n e r a l ) 
5 1 L i f e S c i e n c e s ( G e n e r a l ) 
5 2 A e r o s p a c e M e d i c i n e 
5 3 B e h a v i o r a l S c i e n c e s 
5 4 M a n / S y s t e m T e c h n o l o g y a n d L i f e S u p p o r t 
5 5 P l a n e t a r y B i o l o g y 
M A T H E M A T I C A L A N D C O M P U T E R S C I E N C E S 
5 9 M a t h e m a t i c a l a n d C o m p u t e r S c i e n c e s 
( G e n e r a l ) 
6 0 C o m p u t e r O p e r a t i o n s a n d H a r d w a r e 
6 1 C o m p u t e r P r o g r a m m i n g a n d S o f t w a r e 
6 2 C o m p u t e r S y s t e m s 
6 3 C y b e r n e t i c s 
6 4 N u m e r i c a l A n a l y s i s 
6 5 S t a t i s t i c s a n d P r o b a b i l i t y 
6 6 S y s t e m s A n a l y s i s 
6 7 T h e o r e t i c a l M a t h e m a t i c s 
P H Y S I C S 
7 0 P h y s i c s ( G e n e r a l ) 
7 1 A c o u s t i c s 
7 2 A t o m i c a n d M o l e c u l a r P h y s i c s 
7 3 N u c l e a r a n d H i g h - E n e r g y P h y s i c s 
7 4 O p t i c s 
7 5 P l a s m a P h y s i c s 
7 6 S o l i d - S t a t e P h y s i c s 
7 7 T h e r m o d y n a m i c s a n d S t a t i s t i c a l P h y s i c s 
C 23 
CC62 ANJANEYULU 
SOCIAL SCIENCES 
80 Social Sc iences (General) 
81 A d m i n i s t r a t i o n and Managemen t 
82 Documenta t ion and Informat ion Science 
83 E c o n o m i c s and Cost Ana lys i s 
84 Law and Po l i t i c a l Science 
85 Urban Technology and T r a n s p o r t a t i o n 
SPACE SCIENCES 
88 Space Science (Genera l ) 
89 A s t r o n o m y 
90 A s t r o p h y s i c s 
91 L u n a r and P l a n e t a r y Exp lo ra t ion 
92 So la r P h y s i c s 
93 Space Radia t ion 
GENERAL 
99 G e n e r a l 
BIBLIOGRAPHICAL R E F E R E N C E S 
BHATTACHARYYA (G). F u n d a m e n t a l s 
of subject indexing l anguages . (Pape r 
p r e s e n t e d at the T h i r d In te rna t iona l 
Study Conference in C las s i f i ca t ion 
R e s e a r c h (Bombay) (1975) ) 
DANIELS (P C) and o the r s - T h e s a u r u s 
in act ion I969. (AD 694590). Chap 2 
DEPARTMENT O F DEFENCE ( U S ) . 
Manual for bui lding a technica l thesau-
rus 1966. (AD 633279). Chap 2 
9 
10 
11 
12 
13 
FOSKETT ( A C ) . Subject app roach to 
in format ion I969. Chap 4 . 
GILCHRIST (Alan). T h e s a u r u s in 
r e t r i e v a l . 1971. Chap 2 . 
LANCASTER (F W). Informat ion r e -
t r i e v a l s y s t e m s : C h a r a c t e r i s t i c s 
tes t ing and evaluat ion. 1968 Chap 6, 
Vocabu la ry con t ro l for information 
r e t r i e v a l . 1972 Chap 5. 
MEADOW (C T) . Ana lys i s of informa-
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C 24 


NASA Thesaurus in Information Retrieval

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NASA Thesaurus in Information Retrieval

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