TABLE OF CONTENTS Data implementation is concerned with the mapping of the conceptual data schema to concrete data sources, which enables the publishing (and sometimes the management) of content on the Web. Data implementation occurs in a variety of different scenarios; in most cases, content preexists to the development of the Web application and has to be extracted from external data sources.
From the viewpoint of the database supporting the application, we consider the following cases:
Dedicated database: this situation occurs when the content does not exist prior to the development of the application. In this case, the development of the Web application comprises also the construction of a dedicated database, purposely built for storing the content to be published. Content maintenance is done with an ad hoc application, for example, with content management site views specified in WebML. Typical applications with dedicated databases are B2C and corporate portals, which are conceived specifically to collect and deliver content that is not reused outside the Web application.
Replicated database: this situation occurs when the content is stored in one or more corporate data sources, for example in relational databases or legacy systems, and is periodically copied into a database dedicated to the Web application. The Web application owns and publishes a read-only copy of the corporate data and the original content continues to be created and updated in its native location. An example of this scenario could be an e-commerce Web site that publishes content maintained in the...
