Digital content in Urdu is booming: articles, posts, news. Reading everything is impossible, so an automatic summarizer is needed. So far, "extractive" methods have been used, which cut out key sentences but don’t create new text. Abstractive summarization, however, rewrites the content more naturally, but it’s hard for Urdu because of its complex morphology and right‑to‑left script. A research team tested four transformer models – BERT‑Urdu, BART, mT5 and GPT‑2 – against traditional machine‑learning and deep‑learning approaches. They used three datasets: the Urdu Summarization Corpus, an Urdu fake‑news set, and the Urdu‑Instruct‑News dataset. The results? Transformers, especially mT5, far outperformed classic methods, boosting the F1 score by 0.42 over the best baseline. mT5 handles Urdu challenges well: RTL script, diacritics, and verb‑noun compounds. The experiments also defined optimal hyper‑parameter settings for training. In practice, transformer‑based models are now state‑of‑the‑art for automatic Urdu summarization, with up to a 20 % gain in ROUGE‑L over Seq2Seq models. This work not only reviews past literature but also provides a solid benchmark for future advances.
Technical deep dive: transformer models use self‑attention mechanisms that weight each token against all others, crucial for morphologically rich languages like Urdu. BERT‑Urdu is a bidirectional model pre‑trained on large Urdu corpora, but its architecture is limited to masked language modeling tasks. BART combines encoder‑decoder with denoising pre‑training, useful for generating coherent text, yet its RTL script handling depends on tokenization. mT5, the multilingual version of T5, was trained on 101 languages, including Urdu with a vocabulary of about 250 k tokens. Its encoder‑decoder design lets the summarization be framed as a translation from "full document" to "short summary". GPT‑2, a decoder‑only model, excels at fluent generation but suffers bias toward high‑resource languages. In tests, mT5 showed better diacritic handling thanks to SentencePiece sub‑word tokenization, reducing segmentation errors. Hyper‑parameter tuning included: learning rate 3e‑5, batch size 16, 4‑8 epochs, 10 % warm‑up, gradient clipping at 1.0. Mixed‑precision training cut training time by 30 % on Nvidia A100 GPUs. Evaluation with ROUGE‑1/2/L and F1 metrics revealed mT5 outperforms BART by ~12 % in ROUGE‑L, confirming its superiority for low‑resource languages. These findings suggest that for Urdu, the mix of sub‑word tokenization, encoder‑decoder architecture, and multilingual pre‑training is key to overcoming linguistic challenges.
