A layered architecture for querying dynamic Web content
A layered architecture for querying dynamic Web content
复制标题
用于查询动态 Web 内容的分层架构
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
I. V. Ramakrishnan
中科院分区：
文献类型：
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作者：
H. Davulcu;Juliana Freire;Michael Kifer;I. V. Ramakrishnan
web数据库的设计，即支持基于web的应用程序的数据库系统，目前是一个活跃的研究领域。在本文中，我们提出了一个为期3年的架构，用于设计和实现查询动态Web内容的Web数据库。（只能通过填写多个表单提取的数据）。最低层，即虚拟物理层，通过屏蔽用户从原始Web源检索数据的复杂性来提供导航独立性。其次，传统逻辑层支持站点独立性。顶层类似于传统数据库中的外部模式层。
The design of webbases, database systems for supporting Web-based applications, is currently an active area of research. In this paper, we propose a 3-year architecture for designing and implementing webbases for querying dynamic Web content(i.e., data that can only be extracted by filling out multiple forms). The lowest layer, virtual physical layer, provides navigation independence by shielding the user from the complexities associated with retrieving data from raw Web sources. Next, the traditional logical layer supports site independence. The top layer is analogous to the external schema layer in traditional databases.
Within this architectural framework we address two problems unique to webbases — retrieving dynamic Web content in the virtual physical layer and querying of the external schema by the end user. The layered architecture makes it possible to automate data extraction to a much greater degree than in existing proposals. Wrappers for the virtual physical schema can be created semi-automatically, by asking the webbase designer to navigate through the sites of interest — we call this approach mapping by example. Thus, the webbase designer need not have expertise in the language that maps the physical schema to the raw Web (this should be contrasted to other approaches, which require expertise in various Web-enabled flavors of SQL). For the external schema layer, we propose a semantic extension of the universal relation interface. This interface provides powerful, yet reasonably simple, ad hoc querying capabilities for the end user compared to the currently prevailing “canned” form-based interfaces on the one hand or complex Web-enabling extensions of SQL on the other. Finally, we discuss the implementation of the proposed architecture.