The Realization Of An Extensible Electronic Dictionary

Now we are living in an age of information globalization, and everyday we are sure to meet with the English language. Meeting with new words is inevitable for most of us who haven't learnt English at all and even for some who though have learnt English. New words are barriers against our understanding, and in response, the electronic dictionary is invented to help clients to know the meaning as well as pronunciation of the new words which they meet when they read articles, browse net page, chat online and carry out other daily activities. The electronic dictionary is helpful for our study, life and interpersonal communication. At present, there are already a large number of successful electronic dictionaries in the market. Though they are quite self-contained, some drawbacks still exist in them among which the extensibility is a major aspect. It is well-known that English is an open language and it keeps perfecting itself and introducing new words from other languages for all the time. Thus new words and phrases usually appear or old words obtain new explanation. This requires us to add these new words to the electronic dictionary. Some of the existing electronic dictionaries are able to insert new words, but it employs the strategy which sets up an additional file of new words. Then after being inserted, these new words have to be found in the new-word book and they aren't operated in the same way as the words in original word base. Besides, when vocabulary to be inserted is rather large, the management and search turns out to be very hard. The reason why our electronic dictionary has dynamic extensibility is that we adopt the storage structure and index structure different from average electronic dictionaries. The average electronic dictionaries generally store records by means of byte string and index by means of dense index; the electronic dictionaries with a large vocabulary generally adopt sparse index and multilevel index. Whereas our electronic dictionary adopts a storage technique which is widely used in the database management system----slotted page structure to store variable-length records. It is the improvement of the byte string form. It organizes records within a single block and the actual record start to be continually distributed from the block end, and vacancy are continual which exists between the final entry of the head array and the first record. If a record is inserted, it is located at the end of the vacant room and the entry containing size as well as position of this record is added to the block head. If a record is to be deleted, its occupation room is released and its entry is put in erosion state (for example the size of this record is changed to -1). Besides, the records before the deleted record will be moved. Thus the vacant room due to the deletion can be reused, and all the vacant room locates between the last entry of the head array and the first record again. What's more, the pointer which point to the end of the vacant room in the block head should be revised. When there is vacant room within block, technique similar to this can lengthen or shorten records. Removing records costs not high for there is limitation on the block size which is usually 4KB. In order to make it more convenient for later insertion and deletion, we replace such dynamic index as B tree for static index because the former avoids reconstruction in index when new words are inserted. The integration of the two solves the dynamic insertion of new words more effectively. To achieve a complete electronic dictionary, we also discuss the...