Thanks for your response Grant. You are right, depending of the language we could index the text in a specific field. At request time, we would then ask all the fields for the query.
I see however a few possible problems with this approach. By order of decreasing importance: - Influence on relevance I assume the idf is calculated on a field by field basis? In the context of one field per language, the documents whose language is the less present in the index will receive an unusual boost for cross-lingual tokens. This situation can be quite frequent as the distribution of languages in the index is usually heterogeneous. Even if it was homogeneous, we would have the problem with rare text in one language citing words in another. On the other hand, you are right in the sense that the idf of language specific words is also altered. In the context of one field for all languages, the idf could be very low for a word if it is a common word in another language. For example, the world "thé" in French is quite rare, but its idf would be greatly altered by the word "the" in English. We have a dilemma here... - Performance Queries are in O(log n) if I'm not mistaken? Then a disjunction query on x language fields would be nearly x times slower, no? - Verbose configuration Not an important point, but with the dynamic field type, you configure only one time all the languages. Otherwise, you must do so for each text field. The query handler configuration would also be much more verbose. We usually use the dismax handler and the qf could become very long. - Highlight Not an important point either, but a bit of work need to be done to aggregate the results. In conclusion, the choice is not so clear for me. Your remark on the relevance made me think a bit more on multilingual problems. There may be a way to tune the idf of some fields depending on others? Another idea would be to boost documents in the language of the request. This may be actually much simpler. If you have any idea on the subject I'm very interested! Nicolas -----Message d'origine----- De : Grant Ingersoll [mailto:[EMAIL PROTECTED] Envoyé : vendredi 29 février 2008 14:06 À : solr-user@lucene.apache.org Objet : Re: Proposition of a new feature: Dynamic Field Types Why can't you choose the proper field in your application and keep separate fields per language? Putting them all in the same field, regardless of language, is not a good idea in my opinion because it is more than likely going to skew your statistics and lower your relevance. That being said, the dynamic field type is still an interesting idea. -Grant On Feb 29, 2008, at 5:56 AM, [EMAIL PROTECTED] wrote: > Dynamic field types are field types that act as proxies to other field > types. The choice of the field type to use is done on a per document > basis > and is dependent of the values of the document's fields. > > The use case that led us to this feature is the indexation of > documents in > different languages. We use a specific analyzer for each language > but want > to index semantic information that is not specific to the language. > > For example, we would add in the index the semantic tag {co:Paris} > for the > expressions "Paris", "capital city of France", "the city of lights" in > English and "Paris", "capitale de la France", "la ville lumière" in > French. > This allows us to provide advanced functionalities such as semantic > and > cross-lingual search. > > To do so in SOLR, we chose to index texts written in different > languages in > the same field, while analyzing them with different analyzers. Hence > the > proposition of a new feature that respond to this need: Dynamic > Field Types. > > The idea of this new field type is to act as a proxy to other field > types. > Depending of the values of some fields of the document to index, it > chooses > the correct field type to use. In our situation, we use it to choose > the > correct language dependent field type based on the value of the > field named > "language". It is configured with a config similar to the following: > > <fieldtype name="french_ft" ...> > ... > </fieldtype> > > <fieldtype name="english_ft" ...> > ... > </fieldtype> > > <dynamicFieldType name="multilanguage"> > <fieldtypes> > <fieldtype condition="language:fr" > name="french_ft"/> > <fieldtype condition="language:en" > name="english_ft"/> > <fieldtype condition="*:*" name="english_ft"/> > </fieldtypes> > </dynamicFieldType> > > The last condition is used as a catch-all if preceding conditions > are not > met. > > What do you think of this feature? > > Best regards, > Nicolas Dessaigne
