PDF document search within a very large database

Abstract: Digital search engine, taking a search request from user and then returning a result responded to the request to the user, is indispensable for modern humans who are used to surfing the Internet. On the other hand, the digital document PDF is accepted by more and more people and becomes widely used in this day and age due to the convenience and effectiveness. It follows that, the traditional library has already started to be replaced by the digital one. Combining these two factors, a document based search engine that is able to query a digital document database with an input file is urgently needed. This thesis is a software development that aims to design and implement a prototype of such search engine, and propose latent optimization methods for Loredge. This research can be mainly divided into two categories: Prototype Development and Optimization Analysis. It involves an analytical research on sample documents provided by Loredge and a multi-perspective performance analysis. The prototype contains reading, preprocessing and similarity measurement. The reading part reads in a PDF file by using an imported Java library Apache PDFBox. The preprocessing processes the in-reading document and generates document fingerprint. The similarity measurement is the final stage that measures the similarity between the input fingerprint with all the document fingerprints in the database. The optimization analysis is to balance resource consumptions involving response time, accuracy rate and memory consumption. According to the performance analysis, the shorter the document fingerprint is, the better performance the search program presents. Moreover, a permanent feature database and a similarity based filtration mechanism are proposed to further optimize the program. This project has laid a solid foundation for further study in the document based search engine by providing a feasible prototype and enough relevant experimental data. This study figures out that the following study should mainly focuses on improving the effectiveness of the database access, which involves data entry labeling and search algorithm optimization.