From Apertium
Revision as of 14:30, 25 March 2009 by Unhammer (talk | contribs) (guest free)
Jump to navigation Jump to search

Some languages (in Indo-European particularly Germanic languages) like to make long compound words with low frequency that are unlikely to be found in dictionaries. Typically for any "normal" noun, there can be around 10—100 compound nouns which inflect in exactly the same way (at least for Afrikaans).

  • Afrikaans: infrastruktuurontwikkelingsplan, infrastruktuur+ontwikkelings+plan ("infrastructure development plan"), (cf. personeelverminderingsprosedure, "personnel protection procedure")
  • Dutch : "hulpagina" (help page), "woordbetekenis" (meaning of a word), "inwonertal" (number of inhabitants)
  • German: Kontaktlinsenverträglichkeitstest, Kontakt+linsen+verträglichkeits+test ("contact-lens compatibility test")
  • Danish: Kontaktlinsevæske, Kontaktlinse+væske ("contact-lens liquid")

The presence or absence of a connecting morpheme can sometimes signal a semantic difference, compare:

  • sjefsekretær = 'chief of secretaries' (Norwegian)
  • sjefssekretær = 'the boss's secretary'
  • gjestfri = 'hospitable'
  • gjestefri = 'guest free' (as in "guest free zone")

(gjestfri would typically be listed in the dictionary, gjestefri being compositional.)

There should be some method of attempting to resolve unknown compound words into their constituent parts.

See also the bug report

Outstanding questions

  • Where would compound processing go in the pipeline? Presumably after initial analysis? e.g. in between lt-proc and apertium-tagger.

Proposed algorithms



input: ^*infrastruktuurontwikkelingsplan$

  1. Read word from left to right.
  2. Take the shortest match first from the dictionaries, e.g. infrastruktuurontwikkelingsplan,
    1. Read i-n-f-r-a-s-t-r-u-k-u-u-r (add, because no words have +o)
    2. Read o-n-t-w-i-k-k-e-l-i-n-g-s (add, because no words have +p)
    3. Read p-l-a-n
  3. Output in order.

output: ^infrastruktuur<n><sg>$ ^ontwikkeling<n><pl>$ ^plan<n><sg>$

Left-to-right longest-match

input: ^*infrastruktuurontwikkelingsplan$

  1. Read word from left to right.
  2. Take the longest match first from the dictionaries, e.g. infrastruktuurontwikkelingsplan,
  3. While not found:
    1. Read infrastruktuurontwikkelingsplan
    2. Read infrastruktuurontwikkelingspla
    3. Read infrastruktuurontwikkelingspl
    4. ...
  4. When a word is found, e.g. "infrastruktuur", remove it from the string, put it in the output queue, and start the process again with ontwikkelingsplan.
  5. Output each item from the output queue in order.

output: ^infrastruktuur<n><sg>$ ^ontwikkeling<n><pl>$ ^plan<n><sg>$


If we have translated a string of input words from English to Afrikaans and now want to compound the ones that can be compounded, we have a problem that instead of:


we have:

infrastruktuur ontwikkeling plan

One way of resolving this would be to compile a wordlist (without morphological info) into a tree, and then scan the tree as we scan the output, concatenating words where they appear in the wordlist. Wordlists are substantially more numerous than morphological resources so it would be quite cheap. In order to avoid false-positives, we could just set a length requirement of something like 9 characters or more.

Further reading