“POETIC” STATISTICAL MACHINE TRANSLATION: RHYME AND METER Genzel, Uszkoreit, Och; Google, 2010

Challenge  Automatic translation of poetry is possibly the most difficult problem in Computational Linguistics, MT, and AI.  Few humans are capable of Poetry Translation.  No previous attempts to apply MT to poetry.

Defining Poetry Translation  A poem’s form and meter ( 韻律 ) must be preserved in translation, if at all possible.  Poetic form as constraint of possible translation outputs.  Naïve approach: Perform MT and then use a poem detector among the results.  Better approach: Recast “poem-likeness” as a feature function that has 0 cost, and as a local feature to guide the decoder search.

Reduce Hypothesis Space  H = {h | h is an acceptable translation}  Reduce the size of H  H of poems = {h | h is an acceptable translation, maintains syllable structure ( 音節 ), rhythm( 韻律 ), and rhyme( 押韻 )}

Types of Poetry  Line length: Haiku ( 三行俳句詩 ) (5-7-5)  Rhythmic Poetry: 0 for no stress, 1 for stress (blank verse)  Iambic foot (01)* ( 抑揚格 )  Dactylic foot (100)* ( 揚抑抑格 )  Rhythmic and Rhyming: Sonnet (abbaabbacdecde)  Lines have the same meter  {abab, a:010101, b: }

Stress Pattern Feature Function  Use text-to-speech to capture stress.  Phrase-based: current h-length mod foot length. 2- syllable: 0 or 1, 3-syllable: 0, 1, or 2. Cost is number of mismatches.  Hierarchical: States of how well a partial hypothesis is modeled, length and cost. Can combine states.  “Whatever fits”: modify translation trivially to fit the pattern. Take care to combine right pattern score.

Framework for General Poetic Form Feature Function 1/3

Framework for General Poetic Form Feature Function 2/3  State Space for the feature function:  Current sentence length in syllables  Set of uncovered ranges  Letters from the rhyming scheme

Framework for General Poetic Form Feature Function 3/3

Results  No objective evaluation of “poetic” quality  Test: percentage of sentences that can be translated while maintaining the stress pattern, and the impact of this constraint on the BLEU Score.  Baseline score is 35.33, and stress pattern constrained system is  If we allow no stress errors than 85% of the sentences were matched.  If we allow one stress error than 92% were matched.

Sample Translation