Q: In this task, you will be presented with a context from an academic paper and you have to write an answerable question based on the context. Your questions can be extractive, abstractive, or yes-no questions.
Maximum matching (MM) is one of the most popular fundamental and structural segmentation algorithms for word segmentation BIBREF19 . However, it does not solve the problem of ambiguous words and unknown words that do not exist in the dictionary.
A:
What are the limitations of existing Vietnamese word segmentation systems?