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Communicating with Databases in Natural Language - Wallace M.

Wallace M. Communicating with Databases in Natural Language - Ellis Horwood Limited, 1985. - 170 p.
Download (direct link): comumunicatingwthisdatabase1985.djvu
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PRINT (property name) OF (entity value)
e g,
“PRINT AGE OF EMP:ROBERT”.
(We shall use “(”, “}” throughout to indicate that the word enclosed names a whole class of items which may occur in this position )
We could represent (one use of) the word “is” by the pattern
“What (noun phrase 1) is (noun phrase 2>?”
e g. “What age is Robert?”
“PRINT AGE OF EMP: ROBERT”
is the formal query which represents the meaning of “What age is Robert?”
The statement can be generalised to say:
If “X” is the meaning of NP1 (= noun phrase 1) and “Y” is the meaning of NP2
then “PRINT X OF Y” is the meaning of “What (NP1) is (NP2)?”
The example shows that the meaning of a phrase (or clause) containing a function word is generally dependent on the meaning of the content words in that phrase (or clause).
The example also shows how the traditional grammatical categories (such as ‘noun phrase’) are seldom precise enough to yield a unique meaning for database enquiry. Thus the same pattern — “What (NP1) is (NP2)?” — would also match “What item is ?.50?” although “item” is very unlikely to be represented in any entity/property database as a ‘property’
1.2 Informational restrictions
We have, albeit briefly, discussed how the structural restrictions impinge on the NLU The informational restrictions can, quite simply, confine the NLU to knowledge contained in the database by recognising only those words in the English dictionary which pertain to the data Thus an NLU attached to a personnel database which had no information about families might be asked “Who is
2]
NATURAL LANGUAGE ENQUIRY 19
Smith’s father?”. The NLU’s response, at best, can only be “The database has no information about employees’ families”
(In fact, the way current NLU-database interfaces work, the English dictionary for the NLU only contains words that pertain to the data. The actual response to the “Smith’s father” question in current systems would be: “The word ‘Father’ is not recognised”,)
1.3 “Applicability” restrictions
Some attempt has been made to distinguish informational and structural restrictions because databases with the same structure can contain information on totally different subjects, and databases with different structures may contain information on the same topic, When, however, an NLU is attached to a particular database, the informational and structural restrictions combine to yield tighter restrictions than the sum of both
We have seen how the English query,
“What age is Robert?”
matches the pattern,
What <NP1> is <NP2>?
which maps onto,
PRINT X OF Y
where X is the meaning of “age”, and Y is the meaning of “Robert”
The structural restrictions are:
(1) That the first noun phrase, NP1, maps onto a ‘property’
(2) That the second noun phrase, NP2, maps onto an ‘entity’
(.3) That the sentence “What (NP1> is (NP2)?” is properly represented by the formal query “PRINT (property name) OF (entity value)”.
The informational restrictions are:
(1) That “age” has meaning “X”
(2) That “Robert” has meaning “Y”,
Consider the question “What price is Robert?”, This question appears meaningless (and indeed it may be), but let us suppose that the database contains information, not just about employees and their ages, but also about toys and their prices. Now “What price is Robert (the employee)?” is meaningless, and the formal query
PRINT PRICE OF EMP: ROBERT
will fail
20 NATURAL LANGUAGE ENQUIRY
[Ch
Perhaps, though, there is a toy robot called “Robert”, and the question “What price is Robert” is supposed to yield the formal query
PRINT PRICE OF TOY:ROBERT
The NLU—database interface can select the correct meaning of this query through knowledge of how the information is stored in the structure of the database This produces a new set of restrictions which will only allow queries such as “What <NP1> is (NP2>?” if the property denoted by NP1 is applicable to the entity denoted by NP2 Thus the first meaning, “EMP: ROBERT”, of “Robert” fails to meet the new restrictions, and is rejected in favour of the second meaning, “TOY: ROBERT ”.
These restrictions are called ‘applicability’ restrictions and they can be of considerable use in removing ambiguity from English sentences. A typical example of ambiguity in English is when qualifying phrases occur together:
“The flower in the vase which stood on the mantelpiece . .”
“The shop in the high street which sells flowers .
The second qualifying phrase may qualify either the immediately preceding noun (“the vase which stood on the mantelpiece”), or the first noun (“the shop . . which sells flowers”). People who speak English do not perceive ambiguity in either sentence. Clearly “the flower , „ which stood on the mantelpiece” does not make sense, and nor does “. . , the high street which sells flowers” Instead of extending the NLU’s grammar somehow so as to preclude the ambiguity, it saves duplication of effort to allow the applicability restrictions to remove it.
1,4 Modules in natural language enquiry systems
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