CODAR

Connecting heterogeneous databases through the World Wide Web (WWW) is crucial for most business organizations. The underlying complex problem is the handling of heterogeneity and communication between different data repositories (or database systems). Such interoperability is crucial as it enables the integration of business processes across different business organizations, and therefore becomes a key issue within the new generation of Web-based business applications (called Web Services). CORBA (Common Object Request Broker Architecture) provides protocols and components that allow interoperability between different software platforms (Tari & Bukhres, 2001), such as C++ and Java. However, CORBA does not deal with WWW-based interoperability. In this paper we propose an extension of one of the core elements of CORBA, called Portable Object Adapter (POA), to deal with persistency of business information. The proposed extension, called CODAR, manages the whole life cycle of persistent objects, including activation, deactivation, instantiation, and deletion. At the end of this paper we describe an extension of CODAR to deal with performance by including advanced caching and prefetching techniques.

Protecting Datasources Over the Web

Since the Web is becoming the main means of disseminating information in private and public organizations, both at internal and external levels, several applications at Internet and intranet level need mechanisms supporting a selective access to data available over the Web. Through XML, the document exchange and acquisition processes, which can be very frequent in Web-based systems, are simplified and standardized. The development of suitable security policies for both access control and information release and distribution are relevant research topics in the security field, and XML compatibility is an important requirement for Web datasource protection. This chapter covers the issues related to the definition of security policies, models and mechanisms for access control and dissemination of Web data, and is organized in two parts. In the first part, we introduce the general issues and requirements related to the definition of different types of security policies for access control and for information release in Web datasources. Then, we present security policies and mechanisms specifically devoted to the protection of XML data. In the second part, we describe the use of XML for the specification of security relevant information, focusing on security policies, subject credentials, and content protection.

Web-Powered Databases

Web-powered databases (WPDB) refer both to databases accessible through the Web and to their underlying architecture. This chapter concerns this architecture. It presents the low-level implementation of a WPDB mock-up. The claim which supports the chapter is that this low level analysis can facilitate the understanding of the fundamental mechanisms embedded in a WPDB. All the components of the mock-up, except the Web server itself, are coded in C++. This will illustrate how the techniques such as Internet connections, multitasking, multithreading, and named pipes can be used to develop a WPDB architecture. Moreover, beyond its explanatory aim, the present chapter offers a very practical issue as the C++ codes can be used as a guideline or even more reused as is for the development of more complex WPDBs.

Practical Case Study of a Web-Based Tutor Payment System

The emerging use of object-relational databases with Web technologies has only recently begun. This chapter discusses a practical realization of an application using this technology. The aim is to show readers how to construct a full application from a design using object-oriented features up to the implementation. In this chapter, we highlight important or difficult stages with an emphasis on the mapping of object design into Oracle 8i and the use of stored procedures with the extended features for objects manipulation of Oracle 8i. This enables developers to construct professional Web applications achieving a high modularity and evolution capacity with an accelerated development phase in comparison with the traditional approach.

Web Content Management and Dynamic Web Pages-A Tutorial

Companies nowadays struggle to manage the flood of information that is provided by electronic sources such as the World Wide Web or company-specific information systems. A Web content management system is a useful tool for the collection, structuring and distribution of electronic information within a company. In this tutorial we explain the concepts of a Web content management system and show how to implement such a system based on Java Server pages. Our implementation allows the dynamic generation of Web pages based on interaction with users.

Web Mining to Create a Domain Specific Web Portal Database

The dynamic nature of the World Wide Web is causing an evolution of both information access and format. The use of a Web portal to access information about a domain relieves the searcher of the responsibility to know about, access and retrieve domain documents. In a properly constructed portal, a Web mining process has already sifted through pages found on the Web to select domain facts. This Web-generated knowledge is added to domain expert knowledge in an organized database. This chapter details the design and construction of a domain specific Web portal through the combination of domain expertise and Web-based domain facts.

Cache Management for Web-Powered Databases

The Web has become the primary means for information dissemination. It is ideal for publishing data residing in a variety of repositories, such as databases. In such a multi-tier system (client - Web server - underlying database), where the Web page content is dynamically derived from the database (Web-powered database), cache management is very important in making efficient distribution of the published information. Issues related to cache management are the cache admission/replacement policy, the cache coherency and the prefetching, which acts complementary to caching. The present chapter discusses the issues, which make the Web cache management radically different than the cache management in databases or operating systems. We present a taxonomy and the main algorithms proposed for cache replacement and coherence maintenance. We present three families of predictive prefetching algorithms for the Web and characterize them as Markov predictors. Finally, we give examples of how some popular commercial products deal with the issues regarding the cache management for Web-powered databases.

Ubiquitous Access to Web Databases

With the emergence of the Web, there is a need to provide across-the-board transparency for accessing and manipulating data irrespective of platforms, locations, and systems. The challenge is to build an infrastructure to support flexible tools for information space organization, communication facilities, information discovery, content description, and assembly of data from heterogeneous sources. In this chapter, we describe the WebFINDIT system. WebFINDIT builds a scalable and uniform infrastructure for locating and accessing heterogeneous and autonomous databases in large and dynamic environments. One key feature of WebFINDIT is the clustering of Web databases into distributed ontologies. The main advantage of this ontological organization is filtering interactions and reducing the overhead of locating information. Another important feature is the large spectrum of heterogeneity being supported. Heterogeneity appears at different levels, including hardware (Sun and NT), operating system (UNIX and NT), database (Oracle, Informix, DB2, ObjectStore), and communication middleware (CORBA, DCOM, EJB, and RMI).

Database-Driven Product Catalog System

A Web-based Product Catalog is an online product database that requires easy access from anywhere in the world and uses the most efficient method for information retrieval. The database should support all products no matter what attributes the products have. Many large businesses have been unsuccessful in their attempts to create a product database that enables fast, efficient access across the Web. As there are many complex issues involved with the storage of product information, many companies settle for poorly designed databases as a tradeoff to becoming Web compatible faster. This chapter explores database-driven E-Commerce product catalogs and the issues that inhibit its creation. A Web-based Product Catalog System has been put forward in this chapter that allows for storage of all product specific information. Storage and retrieval of attributes that have no structure, like media objects (pictures, video clips, audio samples) have also been implemented in this system. Media objects are becoming an important feature to product catalogs, especially those intended for deployment on the Internet. Another important feature supported by the system is the ability switch between languages. This multi-language feature allows all of the product information to be understood right around the world, broadening the potential users of the system.

Using Logic for Querying XML Data

In this chapter, we propose the use of first-order logic, in the form of deductive database rules, as a query language for XML data, and we present X-Device, an extension of the deductive object-oriented database system Device, for storing and querying XML data. XML documents are stored into the OODB by automatically mapping the DTD to an object schema. XML elements are treated either as classes or attributes based on their complexity, without loosing the relative order of elements in the original document. Furthermore, this chapter describes the extension of the system’s deductive rule query language with second-order variables, general path and ordering expressions, for querying over the stored, tree-structured XML data and constructing XML documents as a result. The extensions were implemented by translating all the extended features into the basic, first-order deductive rule language of Device using meta-data about stored XML objects.