Release early, release often: English-Chinese dictionary based on Wikipedia

February 16, 2009, [MD]

Background Although there are some great Chinese dictionaries out there, I often encounter cases when they are not enough. I might either be looking for a specific concept, like "open access" (in scholarly publishing) and want to know how that is written in Chinese, so that I can google for articles about it in Chinese. Or I might want to know how Heidegger, Copenhagen or Grey's Anatomy is written in Chinese - a dictionary is unlikely to have any of these (it might have the two first, if it is very complete, but certainly not the last).

Wikipedia is a great, perhaps unintentional, source of these words, because of interwiki links. Each article (usually) has a number of links to articles on the same topic in another language. In the wiki markup, these look like [en:Oslo], and they are listed on the bottom left side of the screen. When, a few days ago, I needed to know about open access in Chinese, I went to the English page on open access, and clicked on the Chinese link, to the page 开放获取.

Data extraction One of the neat things about Wikipedia is that you can download the whole database, and do fun things with the contents. In fact, I tried doing this all the way back in 2007, which gave good results, but I never did anything further (and didn't write it up, since I was in Indonesia, and not blogging, at the time). Recently, a friend of mine has been playing around with dictd servers and files, and this inspired me to take up what I had left.

Luckily, I had pasted the little code snippet I made back then into an email to my friend, and I could find it easily. It worked without any modifications. All I had to do was download the latest Chinese database, an XML file containing all the articles (the file zhwiki-20090116-pages-articles.xml.bz2 in this directory; you can find all the different databases at Wikipedia Downloads). I then ran the Ruby script below, to extract all the titles of articles, and their interwiki links, to a separate, tab-separated text file:

zh = File.open("zhwiki-20090116-pages-articles.xml") zhtitle = File.open("english-chinese.txt","w") title, entitle, hitcounter, counter = '','',0,0

while true counter += 1 if zh.readline.match(/(.?)<\/title>/) title = Regexp::last_match[1] end if line.match(/en:(.?)/) entitle = Regexp::last_match[1] unless title.match(/Wikipedia|User|Help|[A-Za-z]/i) zhtitle << title << "\t" << entitle << "

" hitcounter += 1 if hitcounter == (hitcounter / 100) * 100 puts "In #{counter} articles, found #{hitcounter} hits: #{hitcounter.to_f/counter.to_f*100}%." end end end end

This generates an output file that looks like this

设计模式 Design pattern 中华人民共和国 People's Republic of China 克利斯登·奈加特 Kristen Nygaard 黑客 Hacker (computing) 林纳斯·托瓦兹 Linus Torvalds 理查德·斯托曼 Richard Stallman 自由软件基金会 Free Software Foundation 2003年7月 July 2003 操作系统 Operating system

It's interesting to compare the statistics for this run, and for the run I did in March, 2007. In 2007, the XML dump was 520MB, with 59,600 hits (articles with interwiki links to English). In 2009, the XML dump is 1.1GB, with around 123,300 hits, ie. roughly double both the filesize and hits in two years. As you can see from the small selection above, not all of these are useful (dates, for example), but many are, and would not be found in ordinary dictionaries.

Transforming to simplified and traditional charactersThe Chinese Wikipedia contains articles written in both simplified and traditional characters, and has a built-in facility to convert this on the fly, so that a user can read everything in simplified or traditional according to the settings. Converting from simplified to traditional and back is not trivial, because there are a number of traditional characters that all convert to the same simplified character, etc. Chinese Wikipedia has come up with a great conversion database which deals with this, and once again, we are able to download it and use it for our own purposes.

Back in 2007, a friend of mine downloaded this database, and converted it to a sed script. Sed is an extremely fast command line regexp search-and-replace program for *NIX (also built into OSX). The file looks like this:

s/幾畫/几画/g s/賣畫/卖画/g s/滷鹼/卤碱/g s/原畫/原画/g

each line is an instruction to do global search and replace on for example 幾畫 (traditional) with 几画 (simplified). This is from the traditional->simplified file, there is also a simplified->traditional file. Note that sometimes the conversion isn't simply between characters, but also between words, when different words are used in mainland China and Taiwan. (Download cn->tw and tw->cn sed files).

So instead of having a file that mixed simplified and traditional characters, we can easily generate one with simplified and one with traditional, using sed:

sed -f cntw english-chinese.txt > english-chinese.tw.txt sed -f twcn english-chinese.txt > english-chinese.cn.txt

Instead of doing all this yourself, you can directly download the entire textfile in simplified, or traditional characters (or both, zipped).

Using the fileWith this simple file, you can already do a lot. The simplest is to use grep, a fast command line tool that searches lines in a text file. To quickly search for open access, I would use

grep -i "open access" english-chinese.cn.txt

and get the following result:

开放获取 Open access

the -i means that grep ignores case differences. Note that on my Mac, I cannot see Chinese characters in the terminal window (it might be possible to fix with some settings). An alternative would be to do

grep -i "open access" english-chinese.cn.txt > out.tmp

and then open out.tmp in a text editor that can read UTF8 (unicode). Note that in many text editors you have to specifically ask to open the file as UTF8.

This is cumbersome, but you can of course make different kinds of interfaces to it.

Web interfaceOne simple interface I made was a web interface. Initially I simply ran the grep command through a Ruby wrapper, but I realized that if I executed arbitrary text on the command line, people could use it to infiltrate my server, so I changed to a very simple search. Note that this is not indexed, and is extremely "inefficient" - by putting this into a database, or using something like Ferret, it would be extremely much faster. But it works. Source:

#!/usr/bin/env ruby require 'rubygems' require "fcgi" a = File.read("zhcn-en.txt") FCGI.each_cgi do |cgi| text = cgi['bigger']

search = text.gsub(/\.html/,'') puts "Content-Type: text/html; charset=utf-8" puts "<html><head><title>#{search} |

English-Chinese dictionary" puts ' ' puts "

Search result for #{search}

" puts "

" puts "

" a.each do |line| if line.downcase.match(search.downcase) a,b=line.split("\t") puts " " + a + " " + b + " " end end puts "

" end

I didn't bother writing a form page for it, but the API is extremely simple: http://reganmian.net/en-zh/*searchword*. Here are some examples:

http://reganmian.net/en-zh/Toronto http://reganmian.net/en-zh/open access http://reganmian.net/en-zh/sex

One advantage of the simple search is that it accepts both English and Chinese input, see for example:

http://reganmian.net/en-zh/开放获取

Redirects and disambiguationWhen I initially entered "open access" in English Wikipedia, I arrived at a disambiguation page giving me links to different meanings of the term, one of which, Open access (publishing), was the one I wanted. It is also often the case that abbreviations, people's last names, etc. are redirected to the full article name. I figured it would be useful to have an index of all these disambiguations and redirects, so that I could incorporate that in the database. If, for example, NATO was a redirect to North Atlantic Treaty Alliance, I could have both of those two words function as headwords for the same Chinese term in the dictionary.

And if you looked up open access, I could have (publishing): Chinese term, (infrastructure) different Chinese term, etc. The problem is that I would have to sort through the English database to do this, and the English dump is 7,8GB packed (probably something like 150GB unpacked - pure text). There is also a dump of redirects, however that is just an SQL dump, containing the ID of each article, and the title of the redirect, thus I would have to first import the SQL dump of page titles into a local SQL database. I tried, but it took for ever, and I gave up. This is not impossible, but it will take more time and more programming.

Other dictionary formatsHaving a simple text file is great, you can grep it, and even build simple interfaces, like the web interface I mentioned above. But it would be great if we could also put this database into different dictionaries and lookup programs that already exist.

First I thought about Wenlin. Although it is proprietary, and has not been significantly updated for many years, it is still a very powerful program, which I use frequently when reading texts. I even made a screencast to showcase why I found it so useful. I wondered if it would be possible to import this dictionary into Wenlin. Turns out there is a way to import entries - you need to open a specially formatted textfile in Wenlin, and then choose "import". I was lucky enough to find a very interesting German project to create a German database for Wenlin, and they had a text file that I could use as a model.

The format looks like this:

cidian.db New or changed entries:

*** 1 *** pinyin zàijūliú characters 再拘留 serial-number 1016904350 reference vwu3184a1 part-of-speech v. environment law definition rearrest

With some experimentation, I found that the serial-number and reference had to be there, but could be empty. part-of-spech and environment were not necessary at all. However, I needed two things. First of all, since simplified and traditional characters are not easy to automatically convert, the program requires that you specify both simplified and traditional characters. This was solved by using the scripts above to generate one file for simplified and one for traditional (the same content was on the same lines in each file, so it would be easy to combine them).

In addition, Wenlin requires you to provide the pinyin for each word. This is because some characters have multiple readings, so that it is not easy to automatically generate (correct) pinyin for characters. I didn't need this, but Wenlin required it, and it even checked to see that each pinyin was a possible reading for the given Chinese character. So I needed somehow to get all the words rendered in pinyin.

There are many services, and programs, that convert from Chinese text to pinyin. However, I couldn't find any good command line tools. Command line tools are very good when you are dealing with text files of many megabytes! I tried pasting the text into textfields in Firefox, and in stand-alone applications, and they all choked. Surprisingly, Wenlin itself was able to open the large (around 4MB) file, and it actually has a built-in conversion to pinyin. However, given that this cannot happen automatically, it tags each character with multiple readings, and asks you to select the correct one. I wasn't too preoccupied by having correct readings, just having possible readings that would be accepted by Wenlin would be enough, so I saved the result of the conversion (which took a while). Some lines looked like this:

lín nà sī·tuō 【◎Fix:◎wǎ;◎wà;◎wā】 【◎Fix:◎zī;◎cí】 Linus Torvalds lǐ 【◎Fix:◎chá;◎zhā】 dé·sī tuō màn Richard Stallman

And I had to use the search-and-replace with regexp function in TextMate to remove these options, leaving only the first one (as I mentioned, my goal was not to choose the correct reading, but a possible one).

Combining all three files, I generated the file in Wenlin's required format, however because of all the space required per word, the file became quite large, and Wenlin was unable to cope with it (in fact, even trying to import 100 words automatically failed). I wish there was a command line tool that enabled me to import large amounts of words into Wenlin, but until then, I might have to give this venue up.

Apple's Dictionary.appInitally, I thought that Dictionary.app, which is preinstalled on all Mac's, used dictd files, but it turns out they use some Apple-specific format. Luckily, this is well documented, and there are tools for generating these files included on in the developer package. All you have to do is generate an XML file, which looks something like this

<?xml version="1.0" encoding="UTF-8"?> mathematics 数学 (數學) /d:entry philosophy 哲学 (哲學) /d:entry /d:dictionary

Here is the script I wrote to generate this file:

pinyin = File.open('english-pinyin.txt') cn = File.open('english-chinese.cn.txt') tw = File.open('english-chinese.tw.txt') result = File.open('MyDictionary.xml','w') result << '<?xml version="1.0" encoding="UTF-8"?> ' counter = 0 begin pinyin.each do |line| counter += 1 b, english = cn.readline.split("\t") c, dummy = tw.readline.split("\t") english.gsub!(/((.*))/,'') english.downcase! english.strip! ; b.strip! ; c.strip! result << " #{english} #{b} (#{c}) /d:entry" end rescue end result << "/d:dictionary" result.close

After generating this file (you can download an example here), and editing the MyInfo.plist to reflect the name of the new dictionary, you can run make, and it will churn through, compile the dictionary and generate the index. The finished product (example here) can be installed into your ~/Library/Dictionaries with the command make install or manually, and ideally when you restart Dictionary.app, it will show up.

However, when I compiled the dictionary, I got a number of error messages

"""/Developer/Extras/Dictionary Development Kit"/bin"/ build_dict.sh" "My Dictionary" MyDictionary.xml MyDictionary.css MyInfo.plist - Building My Dictionary.dictionary. *** Invalid index. Skipped -- entry[12504] index 2009-02-16 18:47:30.507 add_supplementary_key[58407:10b] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFString characterAtIndex:]: Range or index out of bounds' 2009-02-16 18:47:30.508 add_supplementary_key[58407: 10b] Stack: (2520711435, (lots of numbers)) /Developer/Extras/Dictionary Development Kit/bin/build_ dict.sh: line 131: 58407 Trace/BPT trap "$DICT_ BUILD_TOOL_BIN"/add_supplementary_key <$OBJECTS_DIR/ normalized_key_body_list_1.txt > $OBJECTS_DIR/normalized_ key_body_list_2.txt *** Unknown format. Skipped [raphael 1222584 0 rapha] - Building key_text index. (things are good...) - Finished building ./objects/My Dictionary.dictionary. echo "Done." Done.

I am quite aware that I didn't read the specs for the file format very carefully, but rather just threw together something that seemed to work - but I must say that the message above is less than meaningful. The actual result, is that a file is produced, and it does work well in Dictionary.app, but it clearly does not contain all the words.

I am not quite enamoured with the Dictionary.app interface, since it only shows a list of headwords, and you have to select a headword to see the translation - different from how the website I mentioned does things. However, it is extremely speedy, and it would be nice if I could solve the problem above.

I might also try to convert the dictionary into an actual dictd file, which should be easier. And I've even thought of merging it somehow with CEDICT to get one large database (I found some perl scripts that might help with this).

ConclusionThis is how far I got in my amateur hacking this time, before it was time to turn back to studies and "more important things". It's interesting that I did a part of this work two years ago, when I wasn't blogging, and therefore didn't document it. These days, I figure I derive so much utility from other people's write ups about their problems and solutions, and neat hacks, that I ought to share my stuff with the world. Perhaps only a few people ever come across it, but to them it might be very useful. Also it's a great personal archive of things too - hadn't I found the script I wrote two years ago in GMail, it might have been lost.

It also shows how useful semantically marked up data can be, especially when a website allows you to download it's entire database and do fun stuff with it, that they never even planned for. (Something similar was the case when I made the Indonesian mouse-over dictionary). There's a large amount of useful tools out there, but they become much more useful if you can run them in command line mode. And there needs to be an easy to use, easy to create, and extract from, format for dictionaries, that all applications can read. (Maybe dictd is it, I need to learn more about it first).

Stian

Stian Håklev Toronto, Canada

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