An Indexing Scheme For Temporal Access Control To XML Documents

XML (Extensible Markup Language) is a normative definition of semantic markup. Its goal is to define a data type which computers and humen are able to indentify easily. With the development of Internet application, especially the further evolvement of e-commerce and web services, data of XML types has become the most popular data form, and the management of XML data has also become a research hotspot.To facilitate the retrieval of information from XML documents,a number of XML query languages have been developed. In order to improve the access performance, a large number of literatures about XML also focus on the research into the indexing techniques for XML documents. At the same time, as more and more sensitive information gets stored in the form of XML, proper access control to the XML documents becomes increasingly important.Access Control Policies of the XML documents specify who can access these documents and how to access the documents. How to access XML documents also includes a series of local problems, such as the way of access, the accessed documents, and the time constraints. In these problems, the time information is particularly important. When the XML documents stored in the database can be accessed, which in the real world are often encountered.For example, to protect a company's business information, only their employees can access the information during working hours, and no one has the right of access the rest of the time.Sophisticated indexing schemes have been proposed to speed up document storage and retrieval. At present, although the existing studies have raised a very wide range of indexing techniques, the study of XML index is only focused on the index for the XML document collections, while corresponding access control information is not indexed. It results in reducing the access performance of the XML documents. To solve the problem, we can construte two indeies respectively for the XML documents and the corresponding access control information. Therefore, the time to make authorization decision is shortened, and the performance of accessing XML documents is improved.In this paper, the study is to propose an indexing mechanism for temporal access control to XML documents.The main works and achievements of this paper are:1. Based on the definiton of authorization term Auth, authorization policy is defined to consist of two parts: one is the time information of authorization plolicy, called Auth_t; the other is the rest information of authorization plolicy, called Auth.2. The authorization policy expressed as the form (Auth_t, Auth) is encoded into bit-vectors, and a bitmap index is constructed.3. It gives the algorithm of authorization processing to process Auth_t of authorization policy.Therefore authorization decision is made, which specifies whether the access to XML documents is permitted.In order to improve efficiency, the indexing schema proposed in this paper creates two indexes: a bitmap index for an XML document collection and a bitmap index for authorization policies.The result of authorization determination is pipelined to the bitmap index of the XML document collection via bit-wise operations that can bridge these two indexes.