SNOMED CT® Release Format 1 (RF1) Guide - ihtsdo

92 | SNOMED CT Release Format 1 (RF1) Guide July 2012
2.3.7.2.4. Example encoding
Table 27: UTF-8 Encoding Example
Character
Unicode
Bytes
0053
S
01010011
0043
C
01000011
2.3.7.3. Check-digit Computation
0054
T
01010100
11000010
®
00AE
10101110
11101111
2462
10111111
10111111
The SCTID (See Component features - Identifiers (2.1.1.4.2)) includes a check-digit, which is generated using
Verhoeff's dihedral check. This section explains the algorithm used and includes sample source code for
generating and checking the check-digit in Java Script and Microsoft Visual Basic.
2.3.7.3.1. Verhoeff's Dihedral Group D5 Check
The mathematical description of this technique may appear complex but in practice it can be reduced to a
pair of two-dimensional arrays, a single dimensional inverse array and a simple computational procedure.
These three arrays are shown in the following tables.
• The first array contains the result of “Dihedral D5” multiplication;
• The second array consists of 8 rows of which two are defined while the rest are derived by applying the
following formula: F(i, j) = F(i - 1, F(1, j));
• The third array consists of a single row containing the inverse of the Dihedral D5 array it identifies the
location of all the zero values in the first array.
Table 28: Results of Dihedral D5 multiplication
0
1
2
3
4
5
6
7
8
0
0
1
2
3
4
5
6
7
8
1
1
2
3
4
0
9
5
6
7
2
2
3
4
0
1
8
9
5
6
© 2002-2012 International Health Terminology Standards Development Organisation CVR #: 30363434
3
3
4
0
1
2
7
8
9
5
4
4
0
1
2
3
6
7
8
9
5
5
6
7
8
9
0
1
2
3
6
6
7
8
9
5
4
0
1
2
7
7
8
9
5
6
3
4
0
1
8
8
9
5
6
7
2
3
4
0
9
9
5
6
7
8
1
2
3
4