I'm currently working on a project for university. Basically, the task is to implement a basic library management tool (in Java, using the Spring Framework and the Java Persistence API). Part of the software requirement is to be able to add and modify book entries and store them in a database. A book
has multiple properties (title, publication date, ...) and also a specific language. Now, my question is: How do I (neatly) implement that whole concept of "language"? I came up with some ideas, each with its own benefits and trade-offs:
Idea 1:
User Input: plain text field
Database: store language as a string (as an attribute of the book relation)
Pros: very simple to implement
Cons: languages might not be uniform ("english", "en", "English", "ENGLISH", ...), lots of room for human error (typos, ...)
Idea 2:
User Input: drop-down / combo box
Database: predefined language relation, containing all possible languages (e.g. language_id as a foreign key in the book relation)
Pros: languages are uniform (e.g. "English", "German", "Italian", ...), little room for human error
Cons: what is the set of all possible languages? Should/Can some languages be omitted? Is this overkill? Is there too much overhead? What format of languages should be used (human-readable: "English", "english", or more compact: "en", "en-us", ...) ?
Idea 3:
User Input: drop-down / combo box
Source Code: as in idea 2, but now hardcode all possible languages as enumerations in source code
Database: convert the specific enumeration to either a string/ordinal and use it as an attribute in the book relation
Pros: pros of Idea 2 + no hardcoding of language strings in source code (from if language = "english" to if language = Language.ENGLISH)
Cons: cons of Idea 2 + how are the enumerations mapped into the database (string, ordinal , separate relation)? The enumerations and the languages in the database must be "in sync".
To me, Idea 2 might be the "most-reasonable", but I'm still not sure, whether this is actually a "good" approach. Maybe you can help me out.
Separate presentation from business logic.
Use a standardized language code for your internal business logic and data storage. You have a choice of several. I would choose the code used by Java in its Locale class, if that covers your domain’s needs. For example, en for English and fr for French.
For presentation to the user, localize the display name of each language. When the user chooses a language during data-entry you translate that to a language code value for logic and storage.
Use a GUI widget that lets the user pick from a list. For a long list, usually best to use a widget that allows for type-ahead to pick an item as the user types the first few letters of the name.
Get an array of all known Locale objects by calling Locale.getAvailableLocales. Loop those to make a Set, to build a distinct list of language codes.
Or call Locale.getISOLanguages to get list of all 2-letter language codes defined in ISO 639-1. The Locale class also offers the three-letter ISO 639-2 language code. I am not an expert here, so I do not know the difference. But we can see this list of 3 & 2 letter codes defined by ISO 639-1 and 639-2.
To get localized name of a language, pass the user’s preferred locale object to the Locale::getDisplayLanguage method.
String displayNameOfFrenchLanguageForJapaneseUser = Locale.FRENCH.getDisplayLanguage( Locale.JAPAN ) ;
displayNameOfFrenchLanguageForJapaneseUser = フランス語
And for German user.
String displayNameOfFrenchLanguageForGermanUser = Locale.FRENCH.getDisplayLanguage( Locale.GERMAN );
System.out.println( "displayNameOfFrenchLanguageForGermanUser = " + displayNameOfFrenchLanguageForGermanUser );
displayNameOfFrenchLanguageForGermanUser = Französisch
As for defining enums, an Enum is defined at compile time. An Enum cannot be redefined wih additional or fewer items at runtime. Locales and language codes, in contrast, do change occasionally. Upgrading your deployment with a different version of Java may have changes in its known locales. So I would lean towards soft-coding. If your domain applies to a specific number of languages that are unlikely to change, say the Romance languages of Western Europe, then hard-coding with enum might be appropriate.
If you need to track dialects rather than mere broad languages, such as Québec French versus French in general, then you may want to learn about the Common Locale Data Repository (CLDR) now bundled with Java implementations built from OpenJDK.
I am searching for a way to retrieve all variants of the lexeme of a specific word.
Example: running -> (run, runs, ran, running…)
I tried out Stanford NLP according to this post. However, the lemma-annotator only retrieves the lemma (running -> run), not the complete set of variants. Is there a way to do this with Stanford NLP or another Java Lib/Framework?
Clarification: I do not search for a stemmer. Also, I would like to avoid programming a new algorithm from scratch to crawl WordNet or similar dictionaries.
The short answer is that a standard NLP library or toolkit is unlikely to solve this problem. Like Stanford NLP, most libraries will only provide a mapping from word --> lemma. Note that this is a many-to-one function, i.e., the inverse function is not well-defined in a word space. It is, however, a well defined function from the space of words to the space of sets of words (i.e., it's a one-to-many mapping in word-space).
Without some form of explicit mapping being maintained, it is impossible to generate all the variants from a given lemma. This is a theoretical impossibility because lemmatization is a lossy, one-way function.
You can, however, generate a mapping of lemma --> set-of-words without much coding (and definitely without coding a new algorithm):
// Java
Map<String, Set<String>> inverseLemmaMap = new HashMap<>();
// Guava
Multimap<String, String> inverseLemmaMap = HashMultimap.create();
Then, as you annotate your corpus using Stanford NLP, you can obtain the lemma and its corresponding token, and populate the above map (or multimap). This way, after a single pass over your dataset, you will have the required inverse lemmatization.
Note that this will be restricted to the corpus/dataset you are using, and not all words in the English language will be included.
Another note is that people often think that an inflection is uniquely determined by the part of speech. This is incorrect:
String s = "My running was beginning to hurt me. I was running all day."
The first instance of running is tagged NN, while the second instance is the present continuous tense of the verb, tagged VBG. This is what I meant by "lossy, one-way function" earlier in my answer.
See below for 50 tweets about "apple." I have hand labeled the positive matches about Apple Inc. They are marked as 1 below.
Here are a couple of lines:
1|“#chrisgilmer: Apple targets big business with new iOS 7 features http://bit.ly/15F9JeF ”. Finally.. A corp iTunes account!
0|“#Zach_Paull: When did green skittles change from lime to green apple? #notafan” #Skittles
1|#dtfcdvEric: #MaroneyFan11 apple inc is searching for people to help and tryout all their upcoming tablet within our own net page No.
0|#STFUTimothy have you tried apple pie shine?
1|#SuryaRay #India Microsoft to bring Xbox and PC games to Apple, Android phones: Report: Microsoft Corp... http://dlvr.it/3YvbQx #SuryaRay
Here is the total data set: http://pastebin.com/eJuEb4eB
I need to build a model that classifies "Apple" (Inc). from the rest.
I'm not looking for a general overview of machine learning, rather I'm looking for actual model in code (Python preferred).
What you are looking for is called Named Entity Recognition. It is a statistical technique that (most commonly) uses Conditional Random Fields to find named entities, based on having been trained to learn things about named entities.
Essentially, it looks at the content and context of the word, (looking back and forward a few words), to estimate the probability that the word is a named entity.
Good software can look at other features of words, such as their length or shape (like "Vcv" if it starts with "Vowel-consonant-vowel")
A very good library (GPL) is Stanford's NER
Here's the demo: http://nlp.stanford.edu:8080/ner/
Some sample text to try:
I was eating an apple over at Apple headquarters and I thought about
Apple Martin, the daughter of the Coldplay guy
(the 3class and 4class classifiers get it right)
I would do it as follows:
Split the sentence into words, normalise them, build a dictionary
With each word, store how many times they occurred in tweets about the company, and how many times they appeared in tweets about the fruit - these tweets must be confirmed by a human
When a new tweet comes in, find every word in the tweet in the dictionary, calculate a weighted score - words that are used frequently in relation to the company would get a high company score, and vice versa; words used rarely, or used with both the company and the fruit, would not have much of a score.
I have a semi-working system that solves this problem, open sourced using scikit-learn, with a series of blog posts describing what I'm doing. The problem I'm tackling is word-sense disambiguation (choosing one of multiple word sense options), which is not the same as Named Entity Recognition. My basic approach is somewhat-competitive with existing solutions and (crucially) is customisable.
There are some existing commercial NER tools (OpenCalais, DBPedia Spotlight, and AlchemyAPI) that might give you a good enough commercial result - do try these first!
I used some of these for a client project (I consult using NLP/ML in London), but I wasn't happy with their recall (precision and recall). Basically they can be precise (when they say "This is Apple Inc" they're typically correct), but with low recall (they rarely say "This is Apple Inc" even though to a human the tweet is obviously about Apple Inc). I figured it'd be an intellectually interesting exercise to build an open source version tailored to tweets. Here's the current code:
https://github.com/ianozsvald/social_media_brand_disambiguator
I'll note - I'm not trying to solve the generalised word-sense disambiguation problem with this approach, just brand disambiguation (companies, people, etc.) when you already have their name. That's why I believe that this straightforward approach will work.
I started this six weeks ago, and it is written in Python 2.7 using scikit-learn. It uses a very basic approach. I vectorize using a binary count vectorizer (I only count whether a word appears, not how many times) with 1-3 n-grams. I don't scale with TF-IDF (TF-IDF is good when you have a variable document length; for me the tweets are only one or two sentences, and my testing results didn't show improvement with TF-IDF).
I use the basic tokenizer which is very basic but surprisingly useful. It ignores # # (so you lose some context) and of course doesn't expand a URL. I then train using logistic regression, and it seems that this problem is somewhat linearly separable (lots of terms for one class don't exist for the other). Currently I'm avoiding any stemming/cleaning (I'm trying The Simplest Possible Thing That Might Work).
The code has a full README, and you should be able to ingest your tweets relatively easily and then follow my suggestions for testing.
This works for Apple as people don't eat or drink Apple computers, nor do we type or play with fruit, so the words are easily split to one category or the other. This condition may not hold when considering something like #definance for the TV show (where people also use #definance in relation to the Arab Spring, cricket matches, exam revision and a music band). Cleverer approaches may well be required here.
I have a series of blog posts describing this project including a one-hour presentation I gave at the BrightonPython usergroup (which turned into a shorter presentation for 140 people at DataScienceLondon).
If you use something like LogisticRegression (where you get a probability for each classification) you can pick only the confident classifications, and that way you can force high precision by trading against recall (so you get correct results, but fewer of them). You'll have to tune this to your system.
Here's a possible algorithmic approach using scikit-learn:
Use a Binary CountVectorizer (I don't think term-counts in short messages add much information as most words occur only once)
Start with a Decision Tree classifier. It'll have explainable performance (see Overfitting with a Decision Tree for an example).
Move to logistic regression
Investigate the errors generated by the classifiers (read the DecisionTree's exported output or look at the coefficients in LogisticRegression, work the mis-classified tweets back through the Vectorizer to see what the underlying Bag of Words representation looks like - there will be fewer tokens there than you started with in the raw tweet - are there enough for a classification?)
Look at my example code in https://github.com/ianozsvald/social_media_brand_disambiguator/blob/master/learn1.py for a worked version of this approach
Things to consider:
You need a larger dataset. I'm using 2000 labelled tweets (it took me five hours), and as a minimum you want a balanced set with >100 per class (see the overfitting note below)
Improve the tokeniser (very easy with scikit-learn) to keep # # in tokens, and maybe add a capitalised-brand detector (as user #user2425429 notes)
Consider a non-linear classifier (like #oiez's suggestion above) when things get harder. Personally I found LinearSVC to do worse than logistic regression (but that may be due to the high-dimensional feature space that I've yet to reduce).
A tweet-specific part of speech tagger (in my humble opinion not Standford's as #Neil suggests - it performs poorly on poor Twitter grammar in my experience)
Once you have lots of tokens you'll probably want to do some dimensionality reduction (I've not tried this yet - see my blog post on LogisticRegression l1 l2 penalisation)
Re. overfitting. In my dataset with 2000 items I have a 10 minute snapshot from Twitter of 'apple' tweets. About 2/3 of the tweets are for Apple Inc, 1/3 for other-apple-uses. I pull out a balanced subset (about 584 rows I think) of each class and do five-fold cross validation for training.
Since I only have a 10 minute time-window I have many tweets about the same topic, and this is probably why my classifier does so well relative to existing tools - it will have overfit to the training features without generalising well (whereas the existing commercial tools perform worse on this snapshop, but more reliably across a wider set of data). I'll be expanding my time window to test this as a subsequent piece of work.
You can do the following:
Make a dict of words containing their count of occurrence in fruit and company related tweets. This can be achieved by feeding it some sample tweets whose inclination we know.
Using enough previous data, we can find out the probability of a word occurring in tweet about apple inc.
Multiply individual probabilities of words to get the probability of the whole tweet.
A simplified example:
p_f = Probability of fruit tweets.
p_w_f = Probability of a word occurring in a fruit tweet.
p_t_f = Combined probability of all words in tweet occurring a fruit tweet
= p_w1_f * p_w2_f * ...
p_f_t = Probability of fruit given a particular tweet.
p_c, p_w_c, p_t_c, p_c_t are respective values for company.
A laplacian smoother of value 1 is added to eliminate the problem of zero frequency of new words which are not there in our database.
old_tweets = {'apple pie sweet potatoe cake baby https://vine.co/v/hzBaWVA3IE3': '0', ...}
known_words = {}
total_company_tweets = total_fruit_tweets =total_company_words = total_fruit_words = 0
for tweet in old_tweets:
company = old_tweets[tweet]
for word in tweet.lower().split(" "):
if not word in known_words:
known_words[word] = {"company":0, "fruit":0 }
if company == "1":
known_words[word]["company"] += 1
total_company_words += 1
else:
known_words[word]["fruit"] += 1
total_fruit_words += 1
if company == "1":
total_company_tweets += 1
else:
total_fruit_tweets += 1
total_tweets = len(old_tweets)
def predict_tweet(new_tweet,K=1):
p_f = (total_fruit_tweets+K)/(total_tweets+K*2)
p_c = (total_company_tweets+K)/(total_tweets+K*2)
new_words = new_tweet.lower().split(" ")
p_t_f = p_t_c = 1
for word in new_words:
try:
wordFound = known_words[word]
except KeyError:
wordFound = {'fruit':0,'company':0}
p_w_f = (wordFound['fruit']+K)/(total_fruit_words+K*(len(known_words)))
p_w_c = (wordFound['company']+K)/(total_company_words+K*(len(known_words)))
p_t_f *= p_w_f
p_t_c *= p_w_c
#Applying bayes rule
p_f_t = p_f * p_t_f/(p_t_f*p_f + p_t_c*p_c)
p_c_t = p_c * p_t_c/(p_t_f*p_f + p_t_c*p_c)
if p_c_t > p_f_t:
return "Company"
return "Fruit"
If you don't have an issue using an outside library, I'd recommend scikit-learn since it can probably do this better & faster than anything you could code by yourself. I'd just do something like this:
Build your corpus. I did the list comprehensions for clarity, but depending on how your data is stored you might need to do different things:
def corpus_builder(apple_inc_tweets, apple_fruit_tweets):
corpus = [tweet for tweet in apple_inc_tweets] + [tweet for tweet in apple_fruit_tweets]
labels = [1 for x in xrange(len(apple_inc_tweets))] + [0 for x in xrange(len(apple_fruit_tweets))]
return (corpus, labels)
The important thing is you end up with two lists that look like this:
([['apple inc tweet i love ios and iphones'], ['apple iphones are great'], ['apple fruit tweet i love pie'], ['apple pie is great']], [1, 1, 0, 0])
The [1, 1, 0, 0] represent the positive and negative labels.
Then, you create a Pipeline! Pipeline is a scikit-learn class that makes it easy to chain text processing steps together so you only have to call one object when training/predicting:
def train(corpus, labels)
pipe = Pipeline([('vect', CountVectorizer(ngram_range=(1, 3), stop_words='english')),
('tfidf', TfidfTransformer(norm='l2')),
('clf', LinearSVC()),])
pipe.fit_transform(corpus, labels)
return pipe
Inside the Pipeline there are three processing steps. The CountVectorizer tokenizes the words, splits them, counts them, and transforms the data into a sparse matrix. The TfidfTransformer is optional, and you might want to remove it depending on the accuracy rating (doing cross validation tests and a grid search for the best parameters is a bit involved, so I won't get into it here). The LinearSVC is a standard text classification algorithm.
Finally, you predict the category of tweets:
def predict(pipe, tweet):
prediction = pipe.predict([tweet])
return prediction
Again, the tweet needs to be in a list, so I assumed it was entering the function as a string.
Put all those into a class or whatever, and you're done. At least, with this very basic example.
I didn't test this code so it might not work if you just copy-paste, but if you want to use scikit-learn it should give you an idea of where to start.
EDIT: tried to explain the steps in more detail.
Using a decision tree seems to work quite well for this problem. At least it produces a higher accuracy than a naive bayes classifier with my chosen features.
If you want to play around with some possibilities, you can use the following code, which requires nltk to be installed. The nltk book is also freely available online, so you might want to read a bit about how all of this actually works: http://nltk.googlecode.com/svn/trunk/doc/book/ch06.html
#coding: utf-8
import nltk
import random
import re
def get_split_sets():
structured_dataset = get_dataset()
train_set = set(random.sample(structured_dataset, int(len(structured_dataset) * 0.7)))
test_set = [x for x in structured_dataset if x not in train_set]
train_set = [(tweet_features(x[1]), x[0]) for x in train_set]
test_set = [(tweet_features(x[1]), x[0]) for x in test_set]
return (train_set, test_set)
def check_accurracy(times=5):
s = 0
for _ in xrange(times):
train_set, test_set = get_split_sets()
c = nltk.classify.DecisionTreeClassifier.train(train_set)
# Uncomment to use a naive bayes classifier instead
#c = nltk.classify.NaiveBayesClassifier.train(train_set)
s += nltk.classify.accuracy(c, test_set)
return s / times
def remove_urls(tweet):
tweet = re.sub(r'http:\/\/[^ ]+', "", tweet)
tweet = re.sub(r'pic.twitter.com/[^ ]+', "", tweet)
return tweet
def tweet_features(tweet):
words = [x for x in nltk.tokenize.wordpunct_tokenize(remove_urls(tweet.lower())) if x.isalpha()]
features = dict()
for bigram in nltk.bigrams(words):
features["hasBigram(%s)" % ",".join(bigram)] = True
for trigram in nltk.trigrams(words):
features["hasTrigram(%s)" % ",".join(trigram)] = True
return features
def get_dataset():
dataset = """copy dataset in here
"""
structured_dataset = [('fruit' if x[0] == '0' else 'company', x[2:]) for x in dataset.splitlines()]
return structured_dataset
if __name__ == '__main__':
print check_accurracy()
Thank you for the comments thus far. Here is a working solution I prepared with PHP. I'd still be interested in hearing from others a more algorithmic approach to this same solution.
<?php
// Confusion Matrix Init
$tp = 0;
$fp = 0;
$fn = 0;
$tn = 0;
$arrFP = array();
$arrFN = array();
// Load All Tweets to string
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://pastebin.com/raw.php?i=m6pP8ctM');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$strCorpus = curl_exec($ch);
curl_close($ch);
// Load Tweets as Array
$arrCorpus = explode("\n", $strCorpus);
foreach ($arrCorpus as $k => $v) {
// init
$blnActualClass = substr($v,0,1);
$strTweet = trim(substr($v,2));
// Score Tweet
$intScore = score($strTweet);
// Build Confusion Matrix and Log False Positives & Negatives for Review
if ($intScore > 0) {
if ($blnActualClass == 1) {
// True Positive
$tp++;
} else {
// False Positive
$fp++;
$arrFP[] = $strTweet;
}
} else {
if ($blnActualClass == 1) {
// False Negative
$fn++;
$arrFN[] = $strTweet;
} else {
// True Negative
$tn++;
}
}
}
// Confusion Matrix and Logging
echo "
Predicted
1 0
Actual 1 $tp $fp
Actual 0 $fn $tn
";
if (count($arrFP) > 0) {
echo "\n\nFalse Positives\n";
foreach ($arrFP as $strTweet) {
echo "$strTweet\n";
}
}
if (count($arrFN) > 0) {
echo "\n\nFalse Negatives\n";
foreach ($arrFN as $strTweet) {
echo "$strTweet\n";
}
}
function LoadDictionaryArray() {
$strDictionary = <<<EOD
10|iTunes
10|ios 7
10|ios7
10|iPhone
10|apple inc
10|apple corp
10|apple.com
10|MacBook
10|desk top
10|desktop
1|config
1|facebook
1|snapchat
1|intel
1|investor
1|news
1|labs
1|gadget
1|apple store
1|microsoft
1|android
1|bonds
1|Corp.tax
1|macs
-1|pie
-1|clientes
-1|green apple
-1|banana
-10|apple pie
EOD;
$arrDictionary = explode("\n", $strDictionary);
foreach ($arrDictionary as $k => $v) {
$arr = explode('|', $v);
$arrDictionary[$k] = array('value' => $arr[0], 'term' => strtolower(trim($arr[1])));
}
return $arrDictionary;
}
function score($str) {
$str = strtolower($str);
$intScore = 0;
foreach (LoadDictionaryArray() as $arrDictionaryItem) {
if (strpos($str,$arrDictionaryItem['term']) !== false) {
$intScore += $arrDictionaryItem['value'];
}
}
return $intScore;
}
?>
The above outputs:
Predicted
1 0
Actual 1 31 1
Actual 0 1 17
False Positives
1|Royals apple #ASGame #mlb # News Corp Building http://instagram.com/p/bBzzgMrrIV/
False Negatives
-1|RT #MaxFreixenet: Apple no tiene clientes. Tiene FANS// error.... PAGAS por productos y apps, ergo: ERES CLIENTE.
In all the examples that you gave, Apple(inc) was either referred to as Apple or apple inc, so a possible way could be to search for:
a capital "A" in Apple
an "inc" after apple
words/phrases like "OS", "operating system", "Mac", "iPhone", ...
or a combination of them
To simplify answers based on Conditional Random Fields a bit...context is huge here. You will want to pick out in those tweets that clearly show Apple the company vs apple the fruit. Let me outline a list of features here that might be useful for you to start with. For more information look up noun phrase chunking, and something called BIO labels. See (http://www.cis.upenn.edu/~pereira/papers/crf.pdf)
Surrounding words: Build a feature vector for the previous word and the next word, or if you want more features perhaps the previous 2 and next 2 words. You don't want too many words in the model or it won't match the data very well.
In Natural Language Processing, you are going to want to keep this as general as possible.
Other features to get from surrounding words include the following:
Whether the first character is a capital
Whether the last character in the word is a period
The part of speech of the word (Look up part of speech tagging)
The text itself of the word
I don't advise this, but to give more examples of features specifically for Apple:
WordIs(Apple)
NextWordIs(Inc.)
You get the point. Think of Named Entity Recognition as describing a sequence, and then using some math to tell a computer how to calculate that.
Keep in mind that natural language processing is a pipeline based system. Typically, you break things in to sentences, move to tokenization, then do part of speech tagging or even dependency parsing.
This is all to get you a list of features you can use in your model to identify what you're looking for.
There's a really good library for processing natural language text in Python called nltk. You should take a look at it.
One strategy you could try is to look at n-grams (groups of words) with the word "apple" in them. Some words are more likely to be used next to "apple" when talking about the fruit, others when talking about the company, and you can use those to classify tweets.
Use LibShortText. This Python utility has already been tuned to work for short text categorization tasks, and it works well. The maximum you'll have to do is to write a loop to pick the best combination of flags. I used it to do supervised speech act classification in emails and the results were up to 95-97% accurate (during 5 fold cross validation!).
And it comes from the makers of LIBSVM and LIBLINEAR whose support vector machine (SVM) implementation is used in sklearn and cran, so you can be reasonably assured that their implementation is not buggy.
Make an AI filter to distinguish Apple Inc (the company) from apple (the fruit). Since these are tweets, define your training set with a vector of 140 fields, each field being the character written in the tweet at position X (0 to 139). If the tweet is shorter, just give a value for being blank.
Then build a training set big enough to get a good accuracy (subjective to your taste). Assign a result value to each tweet, a Apple Inc tweet get 1 (true) and an apple tweet (fruit) gets 0. It would be a case of supervised learning in a logistic regression.
That is machine learning, is generally easier to code and performs better. It has to learn from the set you give it, and it's not hardcoded.
I don't know Python, so I can not write the code for it, but if you were to take more time for machine learning's logic and theory you might want to look the class I'm following.
Try the Coursera course Machine Learning by Andrew Ng. You will learn machine learning on MATLAB or Octave, but once you get the basics you will be able to write machine learning in about any language if you do understand the simple math (simple in logistic regression).
That is, getting the code from someone won't make you able to understand what is going in the machine learning code. You might want to invest a couple of hours on the subject to see what is really going on.
I would recommend avoiding answers suggesting entity recognition. Because this task is a text-classification first and entity recognition second (you can do it without the entity recognition at all).
I think the fastest path to results will be spacy + prodigy.
Spacy has well thought through model for English language, so you don't have to build your own. While prodigy allows quickly create training datasets and fine tune spacy model for your needs.
If you have enough samples, you can have a decent model in 1 day.
I want to be able to parse expressions representing physical quantities like
g/l
m/s^2
m/s/kg
m/(s*kg)
kg*m*s
°F/(lb*s^2)
and so on. In the simplest way possible. Is it possible to do so using something like Pyparsing (if such a thing exists for Java), or should I use more complex tools like Java CUP?
EDIT: To answere MrD's question the goal is to make conversion between quantities, so for example convert g to kg (this one is simple...), or maybe °F/(kg*s^2) to K/(lb*h^2) supposing h is four hour and lb for pounds
This is harder than it looks. (I have done a fair amount of work here). The main problem is there is no standard (I have worked with NIST on units and although they have finally created a markup language few people use it). So it's really a form of natural language processing and has to deal with :
ambiguity (what does "M" mean - meters or mega)
inconsistent punctuation
abbreviations
symbols (e.g. "mu" for micro)
unclear semantics (e.g. is kg/m/s the same as kg/(m*s)?
If you are just creating a toy system then you should create a BNF for the system and make sure that all examples adhere to it. This will use common punctuation ("/", "", "(", ")", "^"). Character fields can be of variable length ("m", "kg", "lb"). Algebra on these strings ("kg" -> 1000"g" has problems as kg is a fundamental unit.
If you are doing it seriously then ANTLR (#Yaugen) is useful, but be aware that units in the wild will not follow a regular grammar due to the inconsistencies above.
If you are REALLY serious (i.e. prepared to put in a solid month), I'd be interested to know. :-)
My current approach (which is outside the scope of your question) is to collect a large number of examples from the literature automatically and create a number of heuristics.
My requirement is to recognize and extract numerical data from a natural language sentence (English only) in response to queries. Platform is Java. For example if the user query is "What is the height of mount Everest" and we have a paragraph as:
In 1856, the Great Trigonometric Survey of British India established the first published height of Everest, then known as Peak XV, at 29,002 ft (8,840 m). In 1865, Everest was given its official English name by the Royal Geographical Society upon recommendation of Andrew Waugh, the British Surveyor General of India at the time, who named it after his predecessor in the post, and former chief, Sir George Everest.[4] Chomolungma had been in common use by Tibetans for centuries, but Waugh was unable to propose an established local name because Nepal and Tibet were closed to foreigners. (Pasted from wikipedia)
For a user query "Height of mount Everest" from the paragraph I need to get 29002 ft or 8840 m as the answer. Can anyone please suggest any possible ways of doing it in Java? Are there any open source libraries for the same?
Obviously, doing this well is extremely difficult to do. If it's an assignment though then I'm guessing the expectation is a bit lower. Here are some thoughts to hopefully get you started:
I'd split the problem into 2 parts; parsing the question block and then passing the answer block. From the question block, you need to know 2 pieces of information, the noun of what you're searching for, and also the type of the answer. In this case the noun is Everest and the type is height. "Types" of data you can build a dictionary for fairly quickly to search your input string for (e.g. "height", "weight", "distance", "age"). The nouns are more difficult, so I'd say to just assume that every non-type in the question is a potential noun, perhaps removing a dictionary of known non-nouns (such as "at", "the", "of" etc.).
Once you've identified the noun and type from the question, you can begin scanning your answer block. I'd begin by breaking that up into sentences. Then scan each sentence for each of your nouns. If one is found in that sentence, you need to scan the sentence again for numbers (taking into account possible whitespace or comma delimiting). Finally, you need to look "around" any numbers you find for a measurement type. So in this case, your "type" that we parsed from the question was "height". You would need to create a mapping of types to measurements, so "height" would map "km, ft, in, cm, m" etc. If the number has one of these types around it, then return the number and measurement type as the answer.
Hope that gets you started. As stated above, this is not intended to be a robust, commercial solution. It's homework-level.