/[webpac]/trunk/doc/exact_match.txt
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Sun Apr 4 20:48:56 2004 UTC (18 years, 3 months ago) by dpavlin
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explanation of bit-masks with examples

1 dpavlin 190 How does exact match work?
2    
3     Well, it's quite stupid because swish-e doesn't allow you to make exact
4     match to words. So, work-around is to add 'xxbxx' word at beginning of
5     string and 'xxexx' word at end (think of it as xxb(egin)xx and xxe(nd)xxx)
6     and then search for phrase (words in particular order).
7    
8     So, title "human" will be indexed as "xxbxx human xxexx" if you want full
9     exact match. Then you can search it using (numbers are parameters to e[nr]
10     field in html forms):
11    
12     1: exact match from beginning "xxbxx human"
13     2: exact match from end "human xxexx" (not really useful)
14     3: exact match begin and end "xxbxx human xxexx"
15    
16     add 4 to those values (numbers are really bit-masks :-) to produce wild-card
17     match:
18    
19     5: exact from beginning with wild-card "xxbxx human*"
20     6: exact from end with wild-card "human* xxexx"
21     7: exact begin+end with wild-card "xxbxx human* xxexx"
22    
23 dpavlin 203 So, to define field which have to be searched using exact match with wild-card
24 dpavlin 190 on TitleAndResponsibility, you would use:
25    
26     <input type="hidden" name="f1" value="TitleAndResponsiblity">
27     <input type="text" name="v1">
28     <input type="hidden" name="e1" value="5">
29    
30 dpavlin 299
31     What are bit-masks?
32    
33     Bit-mask is usage of one byte (8 bits) as 8 separate bits with it's own meaning.
34     So, 1 = 2^1, thus it's bit 1. So, for 1-3 we have:
35    
36     number bits
37     1 01
38     2 10
39     3 11
40    
41     For that we are using two bits. If we want to produce wild-card match, we use
42     bit 3 (2^3 = 4) so we have:
43    
44     number bits
45     1 001 begin
46     2 010 end
47     3 011 begin+end
48     4 100 (not used)
49     5 101 (4+1) begin+wild-card
50     6 110 (4+2) end+wild-card
51     7 111 (4+3) begin+end+wild-card

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