In this paper, we argue that middleware for wired distributed systems cannot be used in a mobile setting, as the principle of transparency that has driven their design runs counter to the new degrees of awareness imposed by mobility. We propose the marriage of reflection and metadata as a means for middleware to give applications dynamic access to information about their execution context. Finally, we describe a conceptual model that provides the basis of our reflective middleware.

Traditionally data warehouses were queried by high level users (executive management, business analysts) only. As the range of potential users with data warehouse access is steadily growing, this assumption is no longer appropriate and the necessity of proper access control mechanisms arises. The security capabilities of available commercial OLAP systems are highly proprietary and the syntax of their security constraints is not suitable for design and documentation purposes. Also, approaches trying to derive the access control policies from the operational data sources have not been very successful, as the relational model is predominate in operational systems while OLAP systems make use of the non-traditional multidimensional model. Access control schemes do not map easily. We approach the issue from the application side by introducing a methodology and a language for conceptual OLAP security design.

OLAP (Online Analysis Processing) applications have very special requirements to the underlying multidimensional data that differs significantly from other areas of application (e.g. the existence of highly structured dimensions). In addition, providing access and search among multiple, heterogeneous, distributed and autonomous data warehouses, especially web warehouses, has become one of the leading issues in data warehouse research and industry. This paper proposes MetaCube-X to provide interoperability search among Web data warehouses.

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The Mobile Agent (MA) paradigm seems to be a promising solution for the design and development of distributed value-added services. However, mobility has added complexity to the design of application and requires new programming methodologies to allow agents to adapt their migration strategies to the current context and to react to unforeseen events. In this paper, we present a policy-based approach to mobility that allows application designers to express and govern mobility decisions at a high level of abstraction and to dynamically change the allocation of agents across the network nodes without intervention on the agent code. Policies are exploited to specify mobility strategies and allow to abstract away the specification of migration choices from the component code. The paper proposes a layered policy-aware architecture for MAs that allows to adapt the mobility behaviour of agents at different levels of abstraction depending on programmer expertise. Unskilled programmers can specify simply when and where to migrate agents, whereas skilled programmers can also specify which migration mechanism to select and activate to better accommodate to environment conditions. We have experienced the dynamicity and flexibility of the proposed approach in the framework obtained by integrating a policy-based management system in a mobile agent environment. 1.

The web, through many search engine sites, has popularized the keyword-based search paradigm, where a user can specify a string of keywords and expect to retrieve relevant documents, possibly ranked by their relevance to the query. Since a lot of information is stored in databases (and not as HTML documents), it is important to provide a similar search paradigm for databases, where users can query a database without knowing the database schema and database query languages such as SQL. In this paper, we propose such a database search system, which accepts a free-form query as a collection of keywords, translates it into queries on the database using the database metadata, and presents query results in a well-structured and browsable form. The system maps keywords onto the database schema and uses inter-relationships (i.e., data semantics) among the referred tables to generate meaningful query results. We also describe our prototype for database search, called Mragyati. The approach proposed here is scalable, as it does not build an in-memory graph of the entire database for searching for relationships among the objects selected by the user’s query.