Question: A translation system produces an English sentence that is clearly worse than the reference translation. Explain why a score comparison is useful in this situation. Identify the two main parts of the system and describe how the comparison tells you which part caused the problem.

Sample answer: A translation system usually has two separate pieces: a function that assigns a numerical score to a candidate translation, and a search procedure that tries to find the best-scoring sentence among an enormous set of possibilities. Because the number of possible translations is far too large to check one by one, the system relies on this search procedure to approximate the best answer.

When the output translation is poor, score comparison helps diagnose the source of the error. If the correct translation receives a better score than the system output, then the scoring function is behaving sensibly and the search procedure likely failed to find the best option. If the system output scores as well as or better than the correct translation, then the scoring function is probably the problem, because it ranked the inferior sentence too highly.

Key points:

• Names the two components as a scoring function and a search procedure.
• Explains that search is approximate because the translation space is extremely large.
• States that a better score for the correct translation points to a search failure.
• States that an equal or better score for the wrong output points to a scoring failure.

Rubric: The essay should identify the scoring function and search procedure, explain why exact search is impractical in translation, and describe how comparing the correct and produced translations separates search errors from scoring errors.