Versus: A Web Repository Daniel Gomes, João P. Campos, Mário J. Silva XLDB Research Group University of Lisbon [dcg, jcampos, Versus is a repository that enables storage, management and access to Web data. Versus enables quick development of Web applications that need to process large amounts of information in a short period of time, using a simple and extensible JAVA API

1st Prototype Features Generic data model –enables storage and management of multi- purpose Web data Time support –enables past views of objects through a versioning system Scalability and distributed operation –enables applications to increase processing capabilities, through the parallel processing of data partitions Extensible meta-data –Enables extension of meta-data information stored in Versus Extensible code –to fulfill specific requirements Web processing applications, with minimum code generation. Well defined API –provides access methods according to the needs of Web applications, supporting different levels of access and performance.

Versus is especially useful for applications that can profit from parallel processing of Web data.

Building a Web Application with Versus 1. Define the application’s unique identifier; 2. Define the partitioning function; 3. Define a conflict resolution policy; 4. Define timeouts for the processing of working units; 5. Write application-specific code for data processing using Versus API.

Data Model An object has a reference to a Web document; A version is a snapshot of an object at a given instant; A layer represents a time unit in the repository; An objectKey is a property associated to an object and therefore to every version of it. A versionProperty is a property associated to a certain version of an object; Xmeta-Data is a container for XML data associated with each version.

Operational Model Archive Workspace: stores data permanently, keeping version history of objects; Group Workspace: maintains a shared view of the data common to all application threads; Private Workspace: provides local storage and fast access to one application thread. Working Units: container for a partition of data, which can be independently processed; Check In/Check Out: operations that move the working units from one workspace to another.

Current & Future Work New Versus –Native XML meta-data –Improve performance –P2P storage server for massive data management and scalable performance Versus applications –TUMBA! (our Web search engine for the Portuguese Web at Web pages repository with history Tarântula V.2 (Web crawler) Tumba’s Index Generator and PageRanker –Performance measurement and analysis –Validation of Versus API. XQuery + XSLT engine tightly coupled with Versus Query engine with access methods and adaptive algorithms

Research on data management. We study and develop systems for data analysis, information integration and user access to large quantities of complex data from heterogeneous sources. Current main project is TUMBA!, a new search engine for the Portuguese Web. Research on: –Integration with Semantic Web –Location-awareness –Web Archiving