C SC 620Advanced Topics in NaturalLanguage ProcessingLecture 133/4Machine Translation• Readings in Machine Translation, Eds. Nirenburg, S. et al. MIT Press2003.• Part 1: Historical Perspective• Reading list:– Introduction. Nirenburg, S.– 1. Translation. Weaver, W.– 3. The Mechanical Determination of Meaning. Reifer, E.– 5. A Framework for Syntactic Translation. Yngve, V.– 6. The Present Status of Automatic Translation of Languages. Bar-Hillel,Y.Paper 3: The Mechanical Determinationof Meaning. E. Reifler• MT Linguistics– MT linguist (vs. traditional linguist)• Mostly concerned with differences in behaviorbetween a given pair of languages• Need not adhere strictly to the results of scientificlanguage research. – When they serve his purpose, he will consider them– He will ignore them when an arbitrary treatment of thelanguage material better suits his purposePaper 3: The Mechanical Determinationof Meaning. E. Reifler• MT Linguistics– MT linguist (vs. traditional linguist)• Practicality is a consideration of the highest order• First concern is source-target semantic agreementand intelligibility– Semantics: a poor relation of linguistics, re-directed topsychologists and philosophersPaper 3: The Mechanical Determinationof Meaning. E. Reifler• The Problem of Editing– Pre-editor• Works with the input language• Determines the intended nongrammatical meaning• Annotates input, resolving ambiguity, specifying which lexemeto pick– Post-editor• Works with the output language (only)• Selects the preferred translation based on output contextPaper 3: The Mechanical Determinationof Meaning. E. Reifler• No Editor– Fully automatic– Or a pre-editor who “instructs the operator ofthe machine to press a special key, with theresult that a mechanical memory selects onlyoutput equivalents characteristic of that branchof knowledge”Paper 3: The Mechanical Determinationof Meaning. E. Reifler• Compound Forms– The mechanical dissection of complexes and their identificationvia the identification of their constituents means that practically nocomplex form, all of whose constituents are prolific and/orproductive, needs to be coded into the mechanical memory. Onlythe prolific and productive constituents need be coded. Theincrease in the number of mechanical operations which such anarrangement implies will be amply compensated for by a reductionin the size of the memory– Examples:• sea- in seaside, seaboard, seaway• -s in seas, boards, waysPaper 3: The Mechanical Determinationof Meaning. E. Reifler• Compound Forms– Three difficulties in extending this analysis• Meaning of a compound often cannot be inferred from itscomponents• X-factor, letter or letter sequence could be part of thepreceding as well as the following constituent– Example (Russian):» Ryb|o|lovu to a fisherman» *Rybolovu to the tin of fishes• Extemporized, i.e. unpredictable, compounds– Examples:» Holdability» (German) Mit|gift with/poison dowryPaper 3: The Mechanical Determinationof Meaning. E. Reifler• The Mechanical Determination of GrammaticalMeaning– Steps:• Meaning of each source form in isolation• Determination of semantic coincidences exhibited bysyntactically correlated co-ocurrences in the input text• Example (German) of grammatical meaning:– den (acc masc sg/dat pl) Männern (dat pl)• Example (German) of nongrammatical meaning:– Er bestand die Prüfung/he passed the exam» bestand -> passedPaper 3: The Mechanical Determinationof Meaning. E. Reifler• The Mechanical Determination of GrammaticalMeaning– Substantives that can also occur as proper names• Can only be resolved by pre-editor• Examples:– Bauer -> farmer– Gerber -> tanner– The “Pinpointing” of Composite Intended Meanings• Mongenetic vs. polygenetic meaning– Pinpointer and pinpointeePaper 3: The Mechanical Determinationof Meaning. E. Reifler• Two Groups of Form Classes– Form Classes with a Very Large Membership• Substantives• Attributive adjectives• Principal verbs• Invariable attributive adjectives derived from substantives bysuffix -er• Predicative adjectives• Adverbs of adjectival origin• Cardinal numbersPaper 3: The Mechanical Determinationof Meaning. E. Reifler• Two Groups of Form Classes– Form Classes with a Comparatively Very Small Membership• Determiners• Pro-substantives• Prepositions• Verbs that take predicate complements: auxiliaries etc.• Separated verb prefixes• Adverbs• Conjunctions• Interjections– Total membership: < 2000Paper 3: The Mechanical Determinationof Meaning. E. Reifler• Memory Systems– Large-Drum System• 4 units– Capital memory for substantives– Attribute adjective memory– Principal verb memory– Predicate adjective memory– Small-Drum System• Individual memory for each operational form class (10-15)– Memory sections• Memory equivalents of all low-frequency forms may be groupedaccording to the number of their component alphabetic and/or non-alphabetic minimal symbols– I.e. use N-symbol sectionsPaper 3: The Mechanical Determinationof Meaning. E. Reifler• Operational Form-Class Filter System– Steps:1. All free initial capital forms directed to capital memory2. Input of the initial letter of all other free forms activates thesmall-drum system3. All source forms which are members of small operationalform classes are identified in processed in the small-drumsystem4. The moment a signal has been fed in which occurs in asequence position not existing in the small-drum system, thelatter is disconnected and the large-drum system isconnected5. Forms thus rejected by the small-drum system are firstdirected to the capital memoryPaper 3: The Mechanical Determinationof Meaning. E. Reifler• Operational Form-Class Filter System– Steps:6. All forms identified in the capital memory are processed there. Freesource forms rejected by the capital memory are, in a fixedsequence, redirected to the other memories7. They are first directed to the attributive adjective memory8. Of forms not identified in 7, the pronominal forms are redirected tothe small-drum system9. All other free forms rejected are directed to the principal verbmemory• V + separable prefix processed by co-occurrence10. All forms rejected in 9 are redirected to the memory for predicateadjectives and adverbs of adjectival and numeral origin11. All source forms not identified so far are forwarded to the outputside in