Natural language processing keywords for building search engine - nlp

I'm recently interested in NLP, and would like to build up search engine for product recommendation. (Actually I'm always wondering about how search engine for Google/Amazon is built up)
Take Amazon product as example, where I could access all "word" information about one product:
Product_Name Description ReviewText
"XXX brand" "Pain relief" "This is super effective"
By applying nltk and gensim packages I could easily compare similarity of different products and make recommendations.
But here's another question I feel very vague about:
How to build a search engine for such products?
For example, if I feel pain and would like to search for medicine online, I'd like to type-in "pain relief" or "pain", whose searching results should include "XXX brand".
So this sounds more like keyword extraction/tagging question? How should this be done in NLP? I know corpus should contain all but single words, so it's like:
["XXX brand" : ("pain", 1),("relief", 1)]
So if I typed in either "pain" or "relief" I could get "XXX brand"; but what about I searched "pain relief"?
I could come up with idea that directly call python in my javascript for calculate similarities of input words "pain relief" on browser-based server and make recommendation; but that's kind of do-able?
I still prefer to build up very big lists of keywords at backends, stored in datasets/database and directly visualized in web page of search engine.
Thanks!

Even though this does not provide a full how-to answer, there are two things that might be helpful.
First, it's important to note that Google does not only treat singular words but also ngrams.
More or less every NLP problem and therefore also information retrieval from text needs to tackle ngrams. This is because phrases carry way more expressiveness and information than singular tokens.
That's also why so called NGramAnalyzers are popular in search engines, be it Solr or elastic. Since both are based on Lucene, you should take a look here.
Relying on either framework, you can use a synonym analyser that adds for each word the synonyms you provide.
For example, you could add relief = remedy (and vice versa if you wish) to your synonym mapping. Then, both engines would retrieve relevant documents regardless if you search for "pain relief" or "pain remedy". However, you should probably also read this post about the issues you might encounter, especially when aiming for phrase synonyms.

Related

Is there a way to get all complete sentences that a search engine (e.g. Google) has indexed that contain two search terms?

as the question says: "Is there a way to get all complete sentences that a search engine (e.g. Google) has indexed that contain two search terms?"
I would like to use the (e.g. Google) search syntax: BMW AND Toyota. (<-- this is just an example)
And I would then like to have returned all sentences that mention BMW and Toyota. They must be in a single (ideally: short) sentence though.
Is that possible?
Many thanks!
PS.: Sorry - I have difficulties finding the right tags for my question... Please feel free to suggest more appropriate ones and I will update the question.
PPS.: Let me rephrase my question: If it is not readily possible with an existing search engine, are there any programmatical ways to do that? Would one have to write a crawler for that purpose?
No this may not be possible, as google stores this info based on keywords and other algorithms.
For any given keyword or set of keywords, google must be maintaining a reference to one or many matching (some accurate, some not so accurate) titles.
I do not work for google, but that could one way they are maintaining their search results.

Methods for extracting locations from text?

What are the recommended methods for extracting locations from free text?
What I can think of is to use regex rules like "words ... in location". But are there better approaches than this?
Also I can think of having a lookup hash table table with names for countries and cities and then compare every extracted token from the text to that of the hash table.
Does anybody know of better approaches?
Edit: I'm trying to extract locations from tweets text. So the issue of high number of tweets might also affect my choice for a method.
All rule-based approaches will fail (if your text is really "free"). That includes regex, context-free grammars, any kind of lookup... Believe me, I've been there before :-)
This problem is called Named Entity Recognition. Location is one of the 3 most studied classes (with Person and Organization). Stanford NLP has an open source Java implementation that is extremely powerful: http://nlp.stanford.edu/software/CRF-NER.shtml
You can easily find implementations in other programming languages.
Put all of your valid locations into a sorted list. If you are planning on comparing case-insensitive, make sure the case of your list already is normalized.
Then all you have to do is loop over individual "words" in your input text and at the start of each new word, start a new binary search in your location list. As soon as you find a no-match, you can skip the entire word and proceed with the next.
Possible problem: multi-word locations such as "New York", "3rd Street", "People's Republic of China". Perhaps all it takes, though, is to save the position of the first new word, if you find your bsearch leads you to a (possible!) multi-word result. Then, if the full comparison fails -- possibly several words later -- all you have to do is revert to this 'next' word, in relation to the previous one where you started.
As to what a "word" is: while you are preparing your location list, make a list of all characters that may appear inside locations. Only phrases that contain characters from this list can be considered a valid 'word'.
How fast are the tweets coming in? As in is it the full twitter fire hose or some filtering queries?
A bit more sophisticated approach, that is similar to what you described is using an NLP tool that is integrated to a gazetteer.
Very few NLP tools will keep up to twitter rates, and very few do very well with twitter because of all of the leet speak. The NLP can be tuned for precision or recall depending on your needs, to limit down performing lockups in the gazetteer.
I recommend looking at Rosoka(also Rosoka Cloud through Amazon AWS) and GeoGravy

How to extract meaningful keywords from a query?

I am working on a project on web intelligence in which I have to build a system which accepts user query and extract meaningful keywords. Say for example user enters a query "How to do socket programming in Java", then I have to ignore "how", "to", "do", "in" and take "socket", "programming", "java" for further processing and clustering e.g. socket and programming are two different meaningful keyword but can be used together as keyword which produce different meaning. I am looking for some algorithm like TF-IDF to approach this problem. Any help will be appreciated.
Well what you are looking into a text analytics solution.
I have only used R for this purpose but one way to look at it is you need a list of words that you consider not meaningful keywords, this is often called "stop words". You can find online lists of stop words for almost any popular language. After doing this you might want to get a couple hundred inputs and calculate the frequency of every keyword there (having already removed stop words, as well as punctuation and having all text in lower-case) and try to identify other keywords that you think are irrelevant and add them to your list of words to remove.
After this there are a ton of options you can explore; an example would be stemming which is getting the core term of each word so that "pages" and "page" are considered the same keyword. (as you go deeper you will find a ton of stuff online to fine-tune your approach)
Hope this helps.

what algorithm does freebase use to match by name?

I'm trying to build a local version of the freebase search api using their quad dumps. I'm wondering what algorithm they use to match names? As an example, if you go to freebase.com and type in "Hiking" you get
"Apo Hiking Society"
"Hiking"
"Hiking Georgia"
"Hiking Virginia's national forests"
"Hiking trail"
Wow, a lot of guesses! I hope I don't muddy the waters too much by not guessing too.
The auto-complete box is basically powered by Freebase Suggest which is powered, in turn, by the Freebase Search service. Strings which are indexed by the search service for matching include: 1) the name, 2) all aliases in the given language, 3) link anchor text from the associated Wikipedia articles and 4) identifiers (called keys by Freebase), which includes things like Wikipedia article titles (and redirects).
How the various things are weighted/boosted hasn't been disclosed, but you can get a feel for things by playing with it for while. As you can see from the API, there's also the ability to do filtering/weighting by types and other criteria and this can come into play depending on the context. For example, if you're adding a record label to an album, topics which are typed as record labels will get a boost relative to things which aren't (but you can still get to things of other types to allow for the use case where your target topic doesn't hasn't had the appropriate type applied yet).
So that gives you a little insight into how their service works, but why not build a search service that does what you need since you're starting from scratch anyway?
BTW, pre-Google the Metaweb search implementation was based on top of Lucene, so you could definitely do worse than using that as your starting point. You can read some of the details in the mailing list archive
Probably they use an inverted Index over selected fields, such as the English name, aliases and the Wikipedia snippet displayed. In your application you can achieve that using something like Lucene.
For the algorithm side, I find the following paper a good overview
Zobel and Moffat (2006): "Inverted Files for Text Search Engines".
Most likely it's a trie with lexicographical order.
There are a number of algorithms available: Boyer-Moore, Smith-Waterman-Gotoh, Knuth Morriss-Pratt etc. You might also want to check up on Edit distance algorithms such as Levenshtein. You will need to play around to see which best suits your purpose.
An implementation of such algorithms is the Simmetrics library by the University of Sheffield.

Synonym style text lookup and parsing

We have a client who is looking for a means to import and categorize a large amount of textual data. This data has to be categorized and it's been suggested that the easiest way to to do this would be to look at the description field and try to match the words held there to see if a category can be derived for that particular record.
It was thought the best way to do this would be matching the words to key words held against each category and if that was unsuccessful then to use some kind of synonym look up to see if this could be used instead. So for example, if a particular record had the word "automobile" in it then a synonym look up could match that word to the word "car" which would be held against the category "vehicle".
Does anyone know of a web service or other means of looking up a dictionary to find synonyms for a particular word? The project manager has suggested buying a Google Enterprise Search license for this but from what I can make out that doesn't offer what these guys are looking for.
Any suggestions of other getting the client what they are looking for would be gratefully accepted.
Thanks! I'll look into Wordnet.
Do you know of any other types of textual classification software products out there. I see there's some discussion of using Bayasian algorithms for this but I can't see any real world examples of it.
The first thing that comes to mind is Wordnet. Wordnet is a human-generated database of words and related words, including synonyms. The Wikipedia Wordnet entry lists several interfaces to Wordnet. I believe some of them are web services.
You can also roll your own. Manning and Schutze's chapter 5 (free PDF) shows ways to do this.
Having said that, are you solving the right problem? How do you build the category list?
Is it a hierarchy? a tag cloud? See Clay Shirky's Ontology is Overrated for a critique of hierarchical categories. I believe that synonyms are less important if you base your classification on sets of words (Naive Bayes, for example) rather than on single words.
You should look at using WordNet. You can visit their website http://wordnet.princeton.edu/ to get more information, but there are libraries available for integrating against them in lots of languages.
Go to their online tool to see the use of it in action here: http://wordnetweb.princeton.edu/perl/webwn. If you look up a word, then click on "S" next to each definition, you'll get a list of semantically related words to that definition.
I also think you should check out software that will allow you to perform "document clustering." Here is an example: http://glaros.dtc.umn.edu/gkhome/cluto/cluto/overview. That should help you bootstrap the category creation process.
I think this will help get you a long way toward what you want!
For text classification you can take a look at Apache Mahout.

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