/[webpac]/branches/humanistika/doc/exact_match.txt
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Sun Apr 4 22:11:13 2004 UTC (15 years, 9 months ago) by dpavlin
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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 303
31     What are bit-masks?
32    
33     Bit-mask is usage of one byte (8 bits) as 8 separate bits with it's own
34     meaning (this is simplification, but bear with me for now).
35    
36     So, 1 = 2^0, thus it's bit 1. With analogy, 2=2^1 and 3=2^0+2^1.
37     So, for 1-3 we use two bits and have:
38    
39     number bits
40     1 01 (just begin bit set)
41     2 10 (just end bit set)
42     3 11 (begin and end bit set)
43    
44     Thus, with two bits (and values 1-3) we can express should we exact match from
45     beginning, end or both. For wild-card match, we use additional bit 3 (2^3 = 4)
46     so we have:
47    
48     number bits exact match
49     1 001 begin
50     2 010 end
51     3 011 begin+end
52     4 100 (not used)
53     5 101 (4+1) begin+wild-card
54     6 110 (4+2) end+wild-card
55     7 111 (4+3) begin+end+wild-card
56    

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