Maybe it's a cultural difference, but I can't imagine why on a query for "John", any of those titles would be treated as anything other than equals - namely, that they are all about John. Maybe the issue is that this seems like a contrived example, and I'm asking for a realistic example. Or, maybe you have some rule of relevance that you haven't yet shared - and I mean rule that a user would comprehend and consider valuable, not simply a mechanical rule.
-- Jack Krupansky On Wed, Apr 20, 2016 at 8:10 PM, <jimi.hulleg...@svensktnaringsliv.se> wrote: > Ok sure, I can try and give some examples :) > > Lets say that we have the following documents: > > Id: 1 > Title: John Doe > > Id: 2 > Title: John Doe Jr. > > Id: 3 > Title: John Lennon: The Life > > Id: 4 > Title: John Thompson's Modern Course for the Piano: First Grade Book > > Id: 5 > Title: I Rode With Stonewall: Being Chiefly The War Experiences of the > Youngest Member of Jackson's Staff from John Brown's Raid to the Hanging of > Mrs. Surratt > > > And in general, when a search word matches the title, I would like to have > the length of the title field influence the score, so that matching > documents with shorter title get a higher score than documents with longer > title, all else considered equal. > > So, when a user searches for "John", I would like the results to be pretty > much in the order presented above. Though, it is not crucial that for > example document 1 comes before document 2. But I would surely want > document 1-3 to come before document 4 and 5. > > In my mind, the fieldNorm is a perfect solution for this. At least in > theory. In practice, the encoding of the fieldNorm seems to make this > function much less useful for this use case. Unless I have missed something. > > Is there another way to achive something like this? Note that I don't want > a general boost on documents with short titles, I only want to boost them > if the title field actually matched the query. > > /Jimi > > ________________________________________ > From: Jack Krupansky <jack.krupan...@gmail.com> > Sent: Thursday, April 21, 2016 1:28 AM > To: solr-user@lucene.apache.org > Subject: Re: Is it possible to configure a minimum field length for the > fieldNorm value? > > I'm not sure I fully follow what distinction you're trying to focus on. I > mean, traditionally length normalization has simply tried to distinguish a > title field (rarely more than a dozen words) from a full body of text, or > maybe an abstract, not things like exactly how many words were in a title. > Or, as another example, a short newswire article of a few paragraphs vs. a > feature-length article, paper, or even book. IOW, traditionally it was more > of a boolean than a broad range of values. Sure, yes, you absolutely can > define a custom similarity with a custom norm that supports a wide range of > lengths, but you'll have to decide what you really want to achieve to tune > it. > > Maybe you could give a couple examples of field values that you feel should > be scored differently based on length. > > -- Jack Krupansky > > On Wed, Apr 20, 2016 at 7:17 PM, <jimi.hulleg...@svensktnaringsliv.se> > wrote: > > > I am talking about the title field. And for the title field, a sweetspot > > interval of 1 to 50 makes very little sense. I want to have a fieldNorm > > value that differentiates between for example 2, 3, 4 and 5 terms in the > > title, but only very little. > > > > The 20% number I got by simply calculating the difference in the title > > fieldNorm of two documents, where one title was one word longer than the > > other title. And one fieldNorm value was 20% larger then the other as a > > result of that. And since we use multiplicative scoring calculation, a > 20% > > increase in the fieldNorm results in a 20% increase in the final score. > > > > I'm not talking about "scores as percentages". I'm simply noting that > this > > minor change in the text data (adding or removing one single word) causes > > the score to change by a almost 20%. I noted this when I renamed a > > document, removing a word from the title, and that single change caused > the > > document to move up several positions in the result list. We don't want > > such minor modifications to have such big impact of the resulting score. > > > > I'm not sure I can agree with you that "the effect of document length > > normalization factor is minimal". Then why does it inpact our result in > > such a big way? And as I said, we don't want to disable it completely, we > > just want it to have a much lesser effect, even on really short texts. > > > > /Jimi > > > > ________________________________________ > > From: Ahmet Arslan <iori...@yahoo.com.INVALID> > > Sent: Thursday, April 21, 2016 12:10 AM > > To: solr-user@lucene.apache.org > > Subject: Re: Is it possible to configure a minimum field length for the > > fieldNorm value? > > > > Hi Jimi, > > > > Please define a meaningful document-lenght range like min=1 max=50. > > By the way you need to reindex every time you change something. > > > > Regarding 20% score change, I am not sure how you calculated that number > > and I assume it is correct. > > What really matters is the relative order of documents. It doesn't mean > > anything addition of a word decreases the initial score by x%. Please > see : > > https://wiki.apache.org/lucene-java/ScoresAsPercentages > > > > There is an information retrieval heuristic which says that addition of a > > non-query term should decrease the score. > > > > Lucene's default document length normalization may favor short document > > too much. But folks blend score with other structural fields > (popularity), > > even completely bypass relevancy score and order by price, production > date > > etc. I mean there are many use cases, the effect of document length > > normalization factor is minimal. > > > > Lucene/Solr is highly pluggable, very easy to customize. > > > > Ahmet > > > > > > On Wednesday, April 20, 2016 11:05 PM, " > > jimi.hulleg...@svensktnaringsliv.se" < > jimi.hulleg...@svensktnaringsliv.se> > > wrote: > > Hi Ahmet, > > > > SweetSpotSimilarity seems quite nice. Some simple testing by throwing > some > > different values at the class gives quite good results. Setting ln_min=1, > > ln_max=2, steepness=0.1 and discountOverlaps=true should give me more or > > less what I want. At least for the title field. I'm not sure what the > > actual effect of those settings would be on longer text fields, so maybe > I > > will use the SweetSpotSimilarity only for the title field to start with. > > > > Of course I understand that there are many things that can be considered > > domain specific requirements, like if to favor/punish short/medium/long > > texts, and how. I was just wondering how many actual use cases there are > > where one want's a ~20% difference in score between two documents, where > > the only difference is that one of the documents has one extra word in > one > > field. (And now I'm talking about an extra word that doesn't affect > > anything else except the fieldNorm value). I for one find it hard to find > > such a use case, and would consider it a very special use case, and would > > consider a more lenient calculation a better fit for most use cases (and > > therefore most domains). :) > > > > /Jimi > > > > > > -----Original Message----- > > From: Ahmet Arslan [mailto:iori...@yahoo.com.INVALID] > > Sent: Wednesday, April 20, 2016 8:14 PM > > To: solr-user@lucene.apache.org > > Subject: Re: Is it possible to configure a minimum field length for the > > fieldNorm value? > > > > Hi Jimi, > > > > SweetSpotSimilarity allows you define a document length range, so that > all > > documents in that range will get same fieldNorm value. > > In your case, you can say that from 1 word up to 100 words do not employ > > document length punishment. If a document is longer than 100 do some > > punishment. > > > > By the way; favoring/punishing short, middle, or long documents is > domain > > specific thing. You are free to decide what to do. > > > > Ahmet > > > > > > > > On Wednesday, April 20, 2016 7:46 PM, " > jimi.hulleg...@svensktnaringsliv.se" > > <jimi.hulleg...@svensktnaringsliv.se> wrote: > > OK. Well, still, the fact that the score increases almost 20% because of > > just one extra term in the field, is not really reasonable if you ask me. > > But you seem to say that this is expected, reasonable and wanted behavior > > for most use case? > > > > I'm not sure that I feel comfortable replacing the default Similarity > > implementation with a custom one. That would just increase the complexity > > of our setup and would make future upgrades harder (we would for example > > have to remember to check if the default similarity configuration or > > implementation changes). > > > > No, if it really is the case that most people like and want this, and > > there is no way to configure Solr/Lucene to calculate fieldNorm in a more > > reasonable way (in my book) for short field values, then I just think we > > are forced to set omitNorms="true", maybe in combination with a simple > > field boost for shorter fields. > > > > /Jimi > > > > > > > > -----Original Message----- > > From: Jack Krupansky [mailto:jack.krupan...@gmail.com] > > Sent: Wednesday, April 20, 2016 5:18 PM > > To: solr-user@lucene.apache.org > > Subject: Re: Is it possible to configure a minimum field length for the > > fieldNorm value? > > > > FWIW, length for normalization is measured in terms (tokens), not > > characters. > > > > With TDIFS similarity (the default before 6.0), the normalization is > based > > on the inverse square root of the number of terms in the field: > > > > return state.getBoost() * ((float) (1.0 / Math.sqrt(numTerms))); > > > > That code is in ClassicSimilarity: > > > > > https://github.com/apache/lucene-solr/blob/releases/lucene-solr/5.5.0/lucene/core/src/java/org/apache/lucene/search/similarities/ClassicSimilarity.java#L115 > > > > You can always write your own custom Similarity class to override that > > calculation. > > > > -- Jack Krupansky > > > > On Wed, Apr 20, 2016 at 10:43 AM, <jimi.hulleg...@svensktnaringsliv.se> > > wrote: > > > > > Hi, > > > > > > In general I think that the fieldNorm factor in the score calculation > > > is quite good. But when the text is short I think that the effect is > two > > big. > > > > > > Ie with two documents that have a short text in the same field, just a > > > few characters extra in of the documents lower the fieldNorm factor too > > much. > > > In one test the text in document 1 is 30 characters long and has > > > fieldNorm 0.4375, and in document 2 the text is 37 characters long and > > > has fieldNorm 0.375. That means that the first document gets almost a > > > 20% higher score simply because of the 7 character difference. > > > > > > What are my options if I want to change this behavior? Can I set a > > > lower character limit, meaning that all fields with a length below > > > this limit gets the same fieldNorm value? > > > > > > I know I can force fieldNorm to be 1 by setting omitNorms="true" for > > > that field, but I would prefer to still have it, just limit its effect > > > on short texts. > > > > > > Regards > > > /Jimi > > > > > > > > > > > >
