# Neural Network-Based Bilingual Lexicon Induction for Indonesian Ethnic Languages
## 4 Results
### Pattern Recall  
To evaluate the neural network-based approach (character-level Bi-LSTM), we define a rule-based approach as the baseline. Minangkabau language experts provided the transformation patterns of the Indonesian language to the Minangkabau language. The steps to generate translation using the rule-based approach are as follows:  
1. Remove the translation pairs, where the source word and the target word are identical from the 2056 translation pair candidates, making 1262 translation pairs. 2. Following the transformation pattern from the expert, define the transformation rules by regular expressions. 3. Use the transformation rules that have been determined with all source words and replace rule matches with a string. There are 34 transformation patterns for the Indonesian to Minangkabau language, as shown in Table 6. However, there are exceptions for pattern numbers 21-27, where the patterns can be grouped by changing all first characters \"e\" to \"a\" and all first characters \"er\" to \"a\". The group can be created using regular expressions (([aiteo]\") e') and (([aiueo]\")er'). The rule-based approach can generate 475 of the 1262 translation pairings, whereas the remaining 787 translation pairs cannot be produced since they have no pattern or have double or multiple patterns. Figure 7 describes the rule-based results. There are several factors affecting the poor performance of the rule-based approach. The rule-based approach is unable to identify two or more patterns in a single word, as shown in Table 7. Only a single pattern can be generated via a rule-based approach. The rule-based approach can be enhanced by identifying multiple rules on a single word, which can potentially increase recall. However, the more rules applied to a single word, the higher the risk of low precision. This thread-off could be explored in future work. Moreover, the current rules listed in Table 6 can be enriched by Minangkabau native speakers to improve their performance. Figure 6: Comparison between SentencePiece with BPE and the character-level method. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Pattern** & **Indonesian** & **Minangkabau** \\ \hline
1 & Ending **uk** to **uak** & [PERSON] & Rusuak \\
2 & Ending **a** to **o** & [PERSON] & Samo \\
3 & Ending **ik** to **iak** & [PERSON] & Batiak \\
4 & Ending **ing** to **iang** & [PERSON] & Baling \\
5 & Remove last character & [PERSON] & Tuka \\
6 & Ending **as** to **eh** & [PERSON] & Paneh \\
7 & Ending **uh** to **uah** & [PERSON] & Penuah \\
8 & Ending **ut** to **uik** & Laut & Lauik \\
9 & Ending **ung** to **uang** & [PERSON] & Patuang \\
10 & Ending **ap** to **ok** & Atap & Atok \\
11 & Ending **it** to **ik** & Kulti & Kulik \\
12 & Ending **is** to **ih** & Lapis & Lapih \\
13 & Ending **up** to **uik** & Hidup & Hiduik \\
14 & Ending **ul** to **ua** & Pukul & Pukua \\
15 & Ending **kan** to **an** & Arahkan & arahan \\
16 & Ending **a** to **ok** & [PERSON] & Jikok \\
17 & Ending **ur** to **ua** & Kabur & Kabua \\
18 & Ending **t** to **ik** & Giat & Giaik \\
19 & Beginning **meng** to **ma** & **Mengadu** & **Maadu** \\
20 & Beginning **meng** to **mang** & Mengaku & **Mangaku** \\
21 & Beginning **Ber** to **Ba** & Berlari & Balari \\
22 & Beginning **Per** to **Pa** & Perjalanan & Pajalanan \\
23 & Beginning **Pe** to **Pa** & Penyabar & Panyaba \\
24 & Beginning **Se** to **Sa** & Seirama & Sairama \\
25 & Beginning **Re** to **Ra** & **Retak** & **Ratak** \\
26 & Beginning **Te** to **Ta** & **Tepian** & **Tapian** \\
27 & Beginning **Ter** to **Ta** & **Termakan** & **Tamakan** \\
28 & Ending **ir** to **ia** & Kincir & Kincia \\
29 & Ending **at **to **ek** & Keringat & Keringek \\
30 & Ending **d** to **ik** & Jasad & Jasaik \\
31 & Ending **id** to **ik** & Murid & Murik \\
32 & Ending **ih** to **iah** & Gigih & Gigih \\
33 & Ending **us** to **uih** & **Arus** & Aruih \\
34 & Ending **il** to **ia** & Hasil & Hasi \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Example words with double or multiple patterns.