/[webpac]/branches/tehnika/doc/exact_match.txt
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Contents of /branches/tehnika/doc/exact_match.txt

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Revision 303 - (show annotations)
Sun Apr 4 22:11:13 2004 UTC (15 years, 8 months ago) by dpavlin
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1 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 So, to define field which have to be searched using exact match with wild-card
24 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
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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