Homework 5: Adding Spell Checking


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Homework 5:
Adding Spell Checking and AutoComplete to Your Search Engine
o Experience using a third-party spell program
o Developing efficient methods for accomplishing autocomplete
In the previous document (AutocompleteInSolr.pdf) you saw how to enhance the Solr program
with spelling correction and an autocomplete (suggest) function. In this exercise you are asked
to use an external spelling correction program in conjunction with Solr and to enhance the
autocomplete functionality of Solr. For spelling correction, you may use an existing third-party
program adapted to your downloaded files. In the case of autocomplete you will need to enhance
your client program that communicates with Solr to deliver autocomplete suggestions to the web
interface you created in an earlier homework
Description of the Exercise
Spelling Correction: in the class lecture you saw a complete spelling correction program
developed by Peter Norvig. The program was written in Python. For this exercise you are
welcome to use whatever third-party spelling program you wish, or you may even write your
own. Since most of you wrote your previous homework client using PhP, you may want to adopt
a version of Norvig’s spelling program written in PhP and run it on your server. You can download
the PhP version of Norvig’s spelling corrector from here:
(you will have to register at the site before being able to download the software, registration is free)
If you prefer to use Norvig’s program in a different language, a wide variety of implementations
can be found at the bottom of this page,
You should make sure to enhance your spelling correction program with a set of terms that are
specific to the news website that you are responsible for. You should make sure that common
terms such as climate, election, etc., and the terms used in the queries of homework #4 are
handled. Norvig’s spell correction program uses a text file(‘’big.txt”) to get set of words to
calculate edit distance. For this you should create your own “big.txt” for your specified news
website. You can use any parser (our suggestion – Apache Tika) and Instructions on using
apache Tika for this purpose can be found here, (
Autocomplete: for the autocomplete portion of the exercise, you will have to modify your
client program, so it accepts single character insertions to the text box, and returns a list of
There are several ways to implement the autocomplete functionality while using Solr. One
possible way is to use the FuzzyLookupFactory
( feature of Solr/Lucene. The
FuzzyLookupFactory creates suggestions for misspelled words in fields. It assumes that what
you’re sending as the suggest.query parameter is the beginning of the suggestion. It will match
terms in your index starting with the provided characters. So, if the query is “ca” it will return all
the words starting with “ca”, e.g. “california” and “carolina” etc. For the first character and
second character that is entered, some autocomplete suggestions should appear.
For this to work you need to enable the suggest component as described in the tutorial but add
some options.
Note: with respect to specific issues about how spelling corrections are displayed or how
autocomplete corrections are displayed you should imitate the way Google handles both. For
example, while typing in the search box, the top suggestions should automatically appear and be
updated as the user keeps typing. The spellcheck suggestion should appear at the top of the
retrieved results. If the word typed is correct no suggestion should appear at the top.
Submission Instructions
You need to place the YouTube URL in your CSCI572/HW5 folder. Please refer
GuidelinesVideoRecordingHW5 for more information on how to create the Youtube video.
Note 1:
Suggested config change for making ‘AND’ as default instead of ‘OR’ for multi-word queries in
Solr default boolean model uses OR instead of AND. So, if your query is “Elon Musk”, then the
result will match all pages which either have ” Elon ” OR ” Musk ” present and not the entire query
” Elon Musk”.To solve this problem, please do as following to set up the standard Query Parser
In solrconfig.xml add this line:
<str name=”q.op”AND</str
within this tag: <requestHandler name=”/select” class=”solr.SearchHandler”
and Inside <lst default tag within requestHandler tag: <lst name=”defaults”
Remember to reload after editing.
Q1. Can we use default spell checker for HW5?
A. You are not supposed to use default spell-checker for Hw5.
Q2. How to handle multi word queries?
A. To handle queries with two words, please handle each word separately.
Q3. Can we use solr’s inbuilt auto-complete features?
A. Yes.
Q4. How should the spell correction and auto complete working look like.
A. Imitate googles auto complete and spell correction, your result should look like that
Q5. when using the php corrector and when loading big.txt, error log says allowed memory size
A. Add the following code, <? php ini_set (‘memory_limit’, ‘1024M’)? at the start of your php
file. This should solve it. If it still doesn’t, change the code to <? php ini_set (‘memory_limit’, –
Q6. Do we need to store user’s history for suggestions?
A. No need to store any user history to get this functionality.
Q7. Do we need to extract the data from all the 17000+ files into big.txt and do we have to avoid
A. Yes, you need to extract the content from all your files. Please Don’t avoid duplicates, please
read how Norvig’s spell correction works, you will find why you need to have duplicates.
Q8. In hw4 it tells us to set the ‘text’ to have a type of “text general”. However, in hw5 it says
A.You can leave as it is. It works just fine.
Q9. Solr exception: Java.lang.String cannot be cast to Java.lang.String
A. please check whether you added suggest component as stated in document(at right place and
with right tags).
Q10. How does big.txt look like?
A. You need to parse content of html files into big.txt. Please refer to
Q11. Do we need to extract the data from all the 17000+ filesinto big.txt and do we have to avoid
A. Yes, you need to extract the content from all your files. Please Don’t avoid duplicates, please
read how Norvig’s spell correction works, If you de-duplicate, then you will defeat the purpose
of using word frequency to estimate P(c), where c is the corrected spelling.
Q12. The document “SpellcheckandAutocompletioninSolr.pdf” is only for reference? For both
spellcheck and autocompletion we don’t use the solr internal functions? We both use external
A. #1 for spell check: You use external program
#2 for Auto completion: You use the one inbuilt in solr.
Q13. If we search “Donad Trup”, when we put “Donad”, the spell check should show “Donald”,
what if we put “Donad Trup”, what spell check should show? Should we combine each spell check
result, like “Donald Trump”, or just show “Donad Trump”, only correct the correct word?
A. Please check for each word separately when you have multiple words in query. You need not
get right spell check for every query you enter. Please have right big.txt will all text as per your
news site. We will take care while grading.
Q14. Can we use the big.txt provided on the Norvig’s website and add query terms from hw4 into
it, or do we have to generate ourselves with Tika?
A. Please generate it. It doesn’t make sense to load all the words from ” The adventures of
sherlock Holmes” in to memory. You might not get correct results too.
Q15. Can we remove the radio button and functionality of page rank here for hw5?
A. No. You can leave it as it was for Hw4.
Q16. I did not do the pagination function on my page. Can we just do top ten results?
A. Pagination is NOT a requirement for this exercise. Top 10 should suffice.
Q17. How should the UI look for auto-suggest feature?
A. Try to imitate the way google works. There should be a dropdown of suggestions when a
character is entered. Also, the suggestions should be clickable. Once a suggestion is clicked, it
should replace the text in the text box.
Q18. Mimicking Google Spell Correction
A. Google handles spelling correction in 2 ways. You can follow any one from the below 2
1. Show result for misspelled word. Just below the text box, you can display the correct
spelling which is clickable. Upon clicking the correct word, it should perform a search and
display the new results.
2. Show results for the spell corrected term. Just below the text box, display the spell
corrected term and the initial misspelled term. Make the misspelled term clickable. Upon
clicking, it should perform a search and display the new results.

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