基于lucene的圖書(shū)搜索引擎的設(shè)計(jì)與實(shí)現(xiàn)外文文獻(xiàn)-資料下載頁(yè)
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【導(dǎo)讀】不同的人用不同的途徑討論同一個(gè)問(wèn)題－――信息超載。其中一些致力于研究新型的用。戶(hù)界面，另一些研究智能代理，其他的則研究如Lucene一樣的精確的搜索工具。入下一章的示例代碼前，我們將向你描述Lucene是什么，不是什么，怎樣起作用。Lucene是一種高性能，可擴(kuò)展的信息檢索的資料庫(kù)。Lucene是一款基于Java語(yǔ)言的，成熟的，免費(fèi)開(kāi)源的項(xiàng)目；它屬于流行的。ApacheJakarta項(xiàng)目下的一個(gè)分支并獲得Apache軟件許可證。因此，Lucene目前已成為幾。年最熱門(mén)的免費(fèi)Java信息檢索類(lèi)庫(kù)。你只需要了解它的少數(shù)類(lèi)用以開(kāi)始整合成為一個(gè)Lucene的。由于Lucene的是一個(gè)Java的資料庫(kù)，它沒(méi)有對(duì)索引和搜尋作出有關(guān)的假設(shè)。Lucene讓您的應(yīng)用程序處理業(yè)務(wù)規(guī)則，與相關(guān)領(lǐng)域有關(guān)，而隱藏在復(fù)雜的索引和搜。一些功能齊全的搜索應(yīng)用程序被建立在Lucene頂層。nutch，larm，jsearch，僅舉幾例。案例研究雙方的nutch和searchblox是包括在第10. Lucene可以索引和搜索任何可以轉(zhuǎn)換為文本格式的數(shù)據(jù)。截至2020年7月，Lucene的與。表表明，Lucene的的發(fā)布?xì)v。其他一些知名的大型跨國(guó)組織正在使用Lucene。
【正文】 xcellent news for developers who need to access Lucene indices from applications written in different languages. You can learn more about some of these ports in chapter 9. Indexing and searching At the heart of all search engines is the concept of indexing: processing the original data into a highly efficient crossreference lookup in order to facilitate rapid searching. Let’s take a quick highlevel look at both the indexing and searching processes. What is indexing, and why is it important? Suppose you needed to search a large number of files, and you wanted to be able to find files that contained a certain word or a phrase. How would you go about writing a program to do this? A na239。ve approach would be to sequentially scan each file for the given word or phrase. This approach has a number of flaws, the most obvious of which is that it doesn’t scale to larger file sets or cases where files are very large. This is where indexing es in: To search large amounts of text quickly, you must first index that text and convert it into a format that will let you search it rapidly, eliminating the slow sequential scanning process. This conversion process is called indexing, and its output is called an index. You can think of an index as a data structure that allows fast random access to words stored inside it. The concept behind it is analogous to an index at the end of a book, which lets you quickly locate pages that discuss certain topics. In the case of Lucene, an index is a specially designed data structure, typically stored on the file system as a set of index files. We cover the structure of index files in detail in appendix B, but for now just think of a Lucene index as a tool that allows quick word lookup. What is searching? Searching is the process of looking up words in an index to find documents where they appear. The quality of a search is typically described using precision and recall metrics. Recall measures how well the search system finds relevant documents, whereas precision measures how well the system filters out the irrelevant documents. However, you must consider a number of other factors when thinking about searching. We already mentioned speed and the ability to quickly search large quantities of text. Support for single and multiterm queries, phrase queries, wildcards, result ranking, and sorting are also important, as is a friendly syntax for entering those queries. Lucene’s powerful software library offers a number of search features, bells, and whistles— so many that we had to spread our search coverage over three chapters (chapters 3, 5, and 6).
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