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Abstract:In order to develop trustworthy information systems, security aspects should be considered from the early project stages. This is particularly true for authorization and access control services, which decide which users can access which parts of the system and in what ways. Software patterns have been used with success to encapsulate best practices in software design. A good collection of patterns is an invaluable aid in designing new systems by inexperienced developers and is also useful to teach and understand difficult problems. Following in this direction, this paper presents a pattern system to describe authorization and access control models. First, we present a set of patterns that include a basic authorization pattern that is the basis for patterns for the wellestablished discretionary and role-based access control models. Metadata access control models have appeared recently to address the high flexibility requirements of open, heterogeneous systems, such as enterprise or e-commerce portals. These models are complex and we use the basic patterns to develop a set of patterns for metadata-based access control.

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With the use of data warehousing and online analytical processing (OLAP) for decision support applications new security issues arise. The goal of this paper is to introduce an OLAP security design methodology, pointing out fields that require further research work. We present possible access control requirements categorized by their complexity. OLAP security mechanisms and their implementations in commercial systems are presented and checked for their suitability to address the requirements.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. However, a data warehouse is primarily built as an open system. Especially exploratory OLAP analysis requires this open nature; security controls may hinder the analytical discovery process.

Knowledge portals make an important contribution to enabling enterprise knowledge management by providing users with a consolidated, personalized user interface that allows efficient access to various types of (structured and unstructured) information. Today's portal systems allow combining access modules to different information sources side by side on a single portal webpage. However, there is no interaction between those so called portlets. When a user navigates within one portlet, the others remain unchanged, which means that each source has to be searched individually for relevant information. This paper discusses integration aspects within enterprise knowledge portals and presents an approach for communicating the user context (revealing the user's information need) among portlets, utilizing Semantic Web technologies. For example, the query context of an OLAP portlet, which provides access to structured data stored in a data warehouse, can be used by an information retrieval portlet in order to automatically provide the user with related documents found in the organization's document management system. The paper shortly presents a prototype that we are building to evaluate our approach, demonstrating such an OLAP and information retrieval integration.