October 1, 1979 KEYWORD STRINGS
RESTRICTIONS ____________
Keyword strings can be no longer than 255 characters in total.
Each Keyword, Attribute, or Value is limited to 16 characters.
not allowed The following characters are ___________ in a Keyword:

SYMBOL NAME REASON ______ ____ ______

; semi-colon Keyword separator
: colon Attribute-Value delimiter
, comma Weight delimiter
&,,¬,(,) boolean operators must be distinguishable for
a retrieval request
b / blank internal restriction

Figure C.1 -- Illegal Keyword Characters ________________________________________
EXAMPLES ________
In a file consisting of popular song titles a user might wish
to distinguish between those for which an author wrote the
music and those for which he wrote the lyrics. The user could
assign the Attribute-Value pairs:
"design;graphics:interactive;text-processing,6" _______________________________________________
this is a Keyword string containing the Keywords "design"
and "text-processing" (the latter with a Weight of 6); it
also contains the Attribute-Value pair
FRESS Resource Manual Release 9.1 FRESS Appendix C.1 -- 269
October 1, 1979 KEYWORD STRINGS
14.2 Boolean Request Format ___________________________
The rules for retrieving Blocks (via BTCONTINUOUS, BTDISCRETE)
and for matching Keywords (SKANNOTATION, SKDISPLAY, SKJUMP) are
the same. They are as follows: With either type of request, a
Keyword in the request will match either a Keyword or the value
part of an Attribute-value pair in the file; e.g., a request for
the Keyword "Irving_Berlin" would be satisfied by either
Attribute-value pair shown in Appendix C.1. An attribute-value
pair will match only another attribute-value pair. In this way
the user can select only that music for which Berlin wrote the
lyrics with no regard to the composer. If the "keys" (Keywords or
attribute-value pairs) match, then Weights are compared (see
Appendix C.1 for a description of Weights). If the request or the
Keyword in the file is unweighted the match is successful. If both
are weighted then the Keyword in the file must have a Weight equal
to or higher than the Keyword in the request in order to satisfy
the request. Boolean combinations of requested Keywords are
satisfied using standard interpretations of the logical operators
"¬" (not), "&" (and), and "" (or), in order of descending
may precedence. The precedence ___ be changed by the use of
parentheses, and is recommended for clarity (see the examples
EXAMPLES ________
bt/Keyword1&key2key3 _____________________
retrieves all Blocks with both Keyword1 and key2, as well as
all Blocks with key3
bt/Keyword1&(key2key3) _______________________
retrieves all Blocks with both Keyword1 and key2, and all
Blocks with both Keyword1 and key3
bt/¬key1 ________
is invalid ___________ since it requests all Blocks which do not have
key1 and it is not permitted to enumerate all Keyworded
Blocks (possibly hundreds).
skd/all& imlac& double ______________________
"turns off" all Blocks which do not have th display keywords
"all." Furthermore, any Block which has either of the
display Keywords "imlac" or "double" is also "turned off".
270 -- Appendix C Release 9.1 FRESS Resource Manual
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