Abstract
In parallel with the recent progress in life sciences, vast numbers of words for new substances and phenom- ena have been appearing. Since 1993, we have been analyzing English texts of medical journals selected mainly from the public MEDLINE database and collecting frequently-used terms together with their frequencies, con- cordances, typical usages, definitions and translations. The data were recorded in a versatile relational database and edited into several text-based, English-Japanese and Japanese-English dictionaries intended for public re- lease. We have also developed convenient online and offline systems for our electronic dictionaries and are providing them on our homepage (http://lsd.pharm.kyoto-u.ac.jp/). The recent 2003 version of the online dic- tionary WebLSD contains 39,790 entries of English terms with their translations and definitions, 26,000 exam- ple sentences for 5,100 words, and 938,000 records of concordances for 9,500 words. The access log statistics of the WebLSD server indicate more than 20,000 searches per day, and the number has been increasing expo- nentially year by year. We are recording the English pronunciations of 5,000 terms using multiple scientists' voices, and the test version of the WebLSD voice was released recently. Since our database can be extended to any language, we are planning to collect Chinese translations of life science terms, with the aim of creating a multi-language life science dictionary that includes English, Japanese and Chinese.
1
Introduction
'Life Science' is a modern academic field that mainly consists of genome-based, molecular and systemic studies on living organisms (i.e. biology), including humans (i.e. medical sciences). Current progress in this field has resulted in vast numbers of research reports describing the findings of new substances or phenomena. Most of these reports are written in English, the practically 'standard' language in n natural sciences, so that Japanese scientists and students have to understand the meaning of new terms and translate them into Japanese for domestic communications. As for the standardization of Japanese scientific terms, there are several thesauri made by governmental institutions. There are also many medical and biological dictionaries in printed format. However, the revision cycles of these publications generally take several years, which are too long for follow- up of new terms. Moreover, there is no information on usage or collocation for the proper use of original Eng- lish terms in the previous scientific dictionaries and thesauri. Such an unsatisfactory situation prompted us to produce a novel dictionary system truly useful for Japanese scientists and students studying life science. 1
2
Life Science Dictionary
Our dictionary is not a simple collection of scientific terms but a flexible database aimed at creating new electronic knowledge-base services. The following sections describe how our system has been constructed.
2.1
Collection of life science terms
In medical sciences, most of the bibliographic citations and author abstracts from more than 4,600 biomedi- cal journals have been accumulated in the MEDLINE database since mid-1960s by the National Library of Medicine, USA. Also, titles and abstracts from biological journals have been compiled into BIOSIS database, which is available from several online distributors. Since most of the scientific terms and concepts have been originated from English literature, we first analyzed the frequency of words appearing in English titles and ab- stracts that were selected from Current Contents Life Science, a quick report version of MEDLINE and BIOSIS databases. By analyzing 1-Gbyte text (12 million words) with our original Perl script, we found that the corpus of 3-year reports consisted of 220,000 types of words and that the number of words vs. frequency level showed an inversely proportional pattern in a logarithmic plot (Fig. 1 left). Detailed inspection of the ranked words revealed that most of the low-frequency words (once or twice in 3 years) were misspellings or particular abbreviations that should not be translated. Furthermore, only 46,270 words of a frequency level of more than 5, corresponding to 21% of the overall types, are required to cover 97.4% of the total 1-Gbyte text (Fig. 1 right), suggesting that a vocabulary of 50,000 words is basically enough for the understanding of cur- rent life science literature, which was set as the tentative target scale of our dictionary. In 1998, the MEDLINE database was opened for public use as free PubMed. Since then, we have periodi- cally analyzed English text from PubMed and collected the differential population of words that involves newly appearing terms (about 2,000 words per year). We have also analyzed several Japanese texts offered by collaborating medical publishers to collect Japanese terms. As of May 2003, approximately 140,000 English and 50,000 Japanese terms have been gathered with their statistical data from multiple sources. Since proper usage of a particular word can be judged by example sentences and concordance, we selected frequently- occurring words and collected 26,000 example sentences for 5,100 words, and 938,000 concordance records for 9,500 words in keyword-in-context (KWIC) format (see below).
2.2
Design of relational database
To compile multiple tables of data systematically, we designed a relational database that can be e asily con- verted into text-base dictionaries (Fig. 2). In the structure, each table contains several fields of records, one of which is a non-redundant set of indices used for defining a relation between different tables. Since many Eng- lish terms correspond to multiple Japanese words and vice versa, there is an intermediate table of translation that defines individual English-Japanese equivalents. Conversions from the relational data to text-base diction- aries were embedded as a function of the database. From the pairs of Kana readings and Kanji characters, a Kana-Kanji conversion dictionary is made for Japanese computer users. Frequency statistics of English words produce a spelling dictionary for word processing software. E-J and J-E dictionaries are made from the core structure of the database, which will be extended to multimedia dictionaries by incorporating voices and video clips in the future. 2.3
Translation and annotation
The translation of words was done by us with help from many volunteer specialists, who made significant contributions in examining the entries. In addition to the equivalent English and Japanese words, each transla- tion record contains some flags indicating part of speech, attribution, commonly-used subfield of life science, and brief explanation, if needed. Tables 1 and 2 summarize the present 56,114 records of translation table in our database. As a collection of words in a particular field of science, two thirds of the records are nouns mainly consisting of anatomical, chemical, taxonomical and methodological terms. Collection of abbreviations is at a preliminary stage because of their redundancy and inconsistency.
* including Latinate nouns, adjectives, adverbs and others.

2.4
Public service of electric dictionary
For the convenience of stand-alone computer users, we have produced electric dictionaries and tools for Kana-Kanji conversion, E-to-J or J-to-E lookup and an English spelling checker. All these files are available for free at our homepage (http://lsd.pharm.kyoto-u.ac.jp/). We have also developed online dictionary systems including a Web-based dictionary WebLSD (Fig. 3), and gloss-embedding systems, WebEtoJ and WebEtoJ_voc (see our another paper by Ohtake et al.). The recent 2003 version of the WebLSD contains 39,790 entries of English terms with their translations and definitions, 26,000 example sentences for 5,100 words, and 938,000 records of concordance records for 9,500 words. We are planning to record the English pronunciations of 5,000 terms using multiple scientists' voices, and the first test version of the WebLSD voice was released recently. A special feature embedded in WebLSD enables a contribution of users to our project. If someone found a new word unregistered in WebLSD, the user can post the word and its translation on a separate page. After validation of the posted word by our collaborators, it is registered to our database, which will be included in the next revision of WebLSD. Through this feedback page, we are receiving more than 200 requests per month. Another characteristic of WebLSD is the abundant information on concordances (Fig. 4), in which a maxi- mum of 300 examples are displayed in KWIC format. Inspection of the concordances will help Japanese scien- tists in writing English sentences correctly. This is the striking advantage of the online dictionary, compared to a dictionary in printed format, because there is no limitation in the size of the electric dictionary. Figure 3 An example of online WebLSD display. A user inputs a query in the lower area with a choice of sev- eral options. The WebLSD server responds to the query by activating either of E-to-J or J-to-E cgi Perl script depending on the character code of the query. In the output, a heading is followed by its frequency level (ranked by the number of asterisks), and links to typical usages, KWIC concordance, and voice. The second and third lines of each record show its translation with reading and synonyms, respectively. Users can con- tribute to our database by posting a new word from the link button. In this example of 'express' appearing in life science articles, it is mostly interpreted as a verb that indicates a transcriptional change from genome DNA to RNA. Consequently, there are some idiomatic phrases frequently used in current molecular biology, of which brief explanations are added before the translation in the case of 'expressed sequence tag' and 'ex- pression vector'. Figure 4   An example of a concordance window in WebLSD. Users can choose the sorting index (actually blue on the display) from the word immediately to the left or right of the relevant word (red on the display). In this example, the user will understand easily that the term 'apoptosis' (cell death by nuclear DNA fragmentation) can be accompanied by the verb ‘undergo’. 3
Conclusion and future perspectives
The Life Science Dictionary project, founded in 1993, is a research project to develop a systematic database for life science terms and tools for the convenience of life scientists. Our services are designed to provide and encourage access within the scientific community to the most up-to-date and comprehensive information on English-Japanese translation of life science terms. Users can make use of the contents of our software for per- sonal use at minimum expense for internet access. The idea has been supported by many users, and the access log statistics of the WebLSD server indicate more than 20,000 searches per day, which is still increasing. In keeping with the users' expectations, we would like to enrich and refine the database records along with the development of life sciences, aiming to be a core virtual knowledge-base in internet cyberspace. In addition, we are planning to collect Chinese translations of life science terms during the next 5 years to facilitate the mutual understanding among Asian scientific communities in the future.
Acknowledgment
This work has been supported by Grants-in-Aid for Publication of Scientific Research Results (1994-2001, 2003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.