Content-based Navigation in a Mini-World Web

Several database query languages have recently been developed to locate and retrieve documents in the vast network of World-Wide Web pages. These languages combine path expressions, which specify the structure of a path through the network to the desired information, with content predicates, which force the path to pass through pages with particular content. The straightforward implementation of these languages is based on breadth-first search of the network, with heavy reliance placed on the user's understanding of network topology to both direct and constrain the search via the appropriate use of the path expressions. In this paper we describe a system that removes the reliance on path expressions to safeguard the search during a query and enables the user to navigate by refining content rather than by specifying structure. Our system uses a cost-constrained model for query evaluation. Links between pages are assigned costs. The user controls how far a query can navigate by specify..

A Jumping Spider to Index Concepts that Span Pages

A search engine can index a concept that appears entirely on a single page. But concepts can span several pages. For instance, a page on trees may be linked to a page on lecture notes for a data structures course. If the trees page does not specifically mention lecture notes, then a search engine search for lecture notes on trees will, at best, only partially match each page. In this paper we describe a strategy to index concepts that span more than one page. Our strategy assumes that a multi-page concept is created by a concept-path, consisting of some number of hyperlinks, that transits through pages with specific content. For instance, there must be a concept-path from the lecture notes page to the trees page to create the lecture notes on trees concept. The key to indexing multi-page concepts is to find the right concept-paths. The paths must be relatively few (certainly much fewer than the overall number of paths in the WWW) or the cost of the index will be too great. At the sa..

Aspect-Oriented Relational Algebra

In this paper we apply the aspect-oriented programming (AOP) paradigm to the relational algebra. AOP is a way to add support for cross-cutting concerns to existing code without directly modifying that code. Data, like code, also has cross-cutting concerns such as versioning, privacy, and reliability. AOP techniques can be used to weave metadata around an application’s data. The metadata imbues the data with additional semantics that must be observed in constraint and query processing. In this paper we show how to modify the relational algebra to process data woven together with metadata. We also analyze the overhead on evaluating an aspect-enhanced query

The Boomerang White Paper: a Page As You Like It

Boomerang is a dynamic HTML page reconfiguration system. A user accesses Boomerang via the Common Gateway Interface. The user supplies a page name and a template, Boomerang fetches the requested page and uses the template to reconfigure it. The template is a sequence of string manipulation rules. The rules are written in a simple regular expression-based pattern matching language. Boomerang also parses HTML variables in forms and query strings and makes those variables available in the template. By taking advantage of Boomerang's dynamic page reconfiguration features, users can easily add navigational links, suppress images, redefine HTML tags, and reshape a page as desired. Since Boomerang is reached through the Common Gateway Interface and understands HTML variables, Boomerang can also be used as a general form-handling script. Several examples are given to show the utility of Boomerang. Boomerang is compatible with existing browsers and servers and does not compromise their securit..

Querying XML data : as you shape it

A limitation of XQuery is that a programmer has to be familiar with the shape of the data to query it effectively. And if that shape changes, or if the shape is other than what the programmer expects, the query may fail. One way to avoid this limitation is to transform the data into a desired shape. A data transformation is a rearrangement of data into a new shape. In this paper, we present the semantics and implementation of XMorph 2.0, a shape-polymorphic data transformation language for XML. An XMorph program can act as a query guard. The guard both transforms data to the shape needed by the query and determines whether and how the transformation potentially loses information, a transformation that loses information may lead to a query yielding an inaccurate result. This paper describes how to use XMorph as a query guard, gives a formal semantics for shape-to-shape transformations, documents how XMorph determines how a transformation potentially loses information, and describes the XMorph implementation