1. Structural Typology across the Subcontinent
Despite distinct genetic origins—Indo-European for Sinhala, Hindi, and Bengali vs. Dravidian for Tamil, Telugu, and Malayalam—over two millennia of intense language contact have forged a profound areal syntactic unity (Sprachbund). Modern computational engines must address shared syntactico-morphological properties:
| Linguistic Dimension | Sinhala (සිංහල) | Tamil (தமிழ்) | Hindi (हिन्दी) |
|---|---|---|---|
| Language Family | Indo-Aryan (Insular Branch) | Dravidian (Southern Branch) | Indo-Aryan (Central Branch) |
| Canonical Word Order | SOV (Subject-Object-Verb) | SOV (Subject-Object-Verb) | SOV (Subject-Object-Verb) |
| Script Type | Sinhala Abugida (Brahmi-derived) | Tamil Script (Vatteluttu/Brahmi) | Devanagari Abugida (Nagari) |
| Unicode Block Range | U+0D80 – U+0DFF | U+0B80 – U+0BFF | U+0900 – U+097F |
| Diglossic SVA Rigor | Extreme (Literary strict, Spoken zero) | High (Both varieties inflect) | Continuous (Full concord) |
| Complex Text Layout (CTL) | Requires ZWJ (U+200D) for Yansaya/Rakaransaya | Ligatures & Vowel Sign Modifiers | Half-forms & Virama Conjuncts |
2. Key Engineering Challenges in Regional Language Models
1. Subword Tokenizer Fragmentation
Off-the-shelf multilingual tokenizers (e.g. Byte-Pair Encoding in GPT or LLaMA) over-segment South Asian words into 4–8 disjointed unicode bytes per word, drastically inflating context windows and degrading reasoning benchmarks.
2. Zero-Width Joiner (ZWJ) Inconsistency
Operating system variations (Windows vs. macOS vs. Android) handle ZWJ codepoints differently. Text inputs copied from legacy fonts (e.g., FM-Abhaya) contaminate datasets with invalid ASCII glyphs that require automated normalization.
3. Morphological Sparsity
Agglutination in Dravidian and rich inflectional paradigms in Indo-Aryan produce millions of unique word forms. Unsupervised methods fail on rare morphological forms without rule-grounded morphological analyzers.
4. Diglossic Annotation Drift
Web-crawled training corpora indiscriminately mix colloquial social media Sinhala with formal legal/journalistic Sinhala, leading neural models to produce ungrammatical hybrid outputs unless constrained by deterministic grammars.
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