A multimedia presentation refers to the presentation of multimedia data using output devices such as monitors for text and video, and speakers f o r audio. Each presentation consists of multimedia segments which are obtained from a multimedia data model. In this paper, we propose to express semantic coherency of a multimedia presentation in terms of presentation inclusion and exclusion constraints that are zncorporated into the multimedia data model. Thus, when a user specifies a set of segments for a presentation, the DBMS adds segments into and/or deletes segments from the set in order to satisfy the inclusion and exclusion constraints. To automate the assembly of a presentation with concurrent presentation streams, we also propose presentation organization constraihts that are incorporated into the multimedia data model, independent of any presentation. W e give two algorithms for automated presentation assembly and discuss their complexity. We discuss the satisfiability of inclusion and exclusion constraints when negation is allowed. And, we briefly describe a prototype system that is being developed for automated presentation assembly.

In this paper, we present a methodology for automated construction of multimedia presentations. Semantic coherency of a multimedia presentation is expressed in terms of presentation inclusion and exclusion constraints. When a user specifies a set of segments for a presentation, the multimedia database system adds segments into and/or deletes segments from the set in order to satisfy the inclusion and exclusion constraints. We discuss the consistency and the satisfiability of inclusion and exclusion constraints when exclusion is allowed. Users express a presentation query by (a) pointing and clicking to an initial set of desired multimedia segments to be included into the presentation, and (b) specifying an upper bound on the time length of the presentation. The multimedia database system then finds the set of segments satisfying the inclusion-exclusion constraints and the time bound. Using priorities for segments and inclusion constraints, we give two algorithms for automated presentation assembly and discuss their complexity. To automate the assembly of a presentation with concurrent presentation streams, we introduce presentation organization constraints that are incorporated into the multimedia data model, independent of any presentation. We define four types of presentation organization constraints that, together with an underlying database ordering, allow us to obtain a unique presentation graph for a given set of multimedia segments. We briefly summarize a prototype system that fully incorporates the algorithms for the segment selection problem.

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Access control models are an important tool developed for securing today’s data systems. Institutions use the access control models specifically to define who their employees are, what they can do, which resources they can reach, and which processes they can perform and use them to manage the whole process. This is a very hard and costly process for institutions with distributed database systems. However, access control models cannot be implemented in a qualified way due to the fact that the conditions for defining users’ demands to reach resources distributed on different servers, one of which is consequentially bound to the other, the verification and authorization of those user demands, and being able to monitor the actions of the users cannot be configured in an efficient way all the time. With our model suggested in this study, the aim is to automatically calculate the permissions and access levels of all users defined in the distributed database systems for the objects, and, in this way, we will reach a more efficient decision as to which objects the users can access while preventing their access to the information they do not need. Our proposed model in this study has been applied to real life data clusters from organizations providing health and education services and a public service. With the proposed model, all models have been run on servers sharing resources in a private network. The performance of the proposed model has been compared to that of traditional access models. It was confirmed that the proposed model presented an access control model providing more accurate access level results as well as being scalable to many distributed database systems.

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Bu çalışmada, dağıtık veritabanlarında bilgi akış denetimi ile veri gizliliği ve kullanıcıların veri mahremiyetini sağlamak amaçlanmıştır. Bu çalışmada; ilk kez 1998 yılında Myer tarafından tanıtılmış olan dağıtık etiket modelinin dağıtık veritabanında gerçekleştirilen tüm işlemler (okuma, yazma, güncelleme, silme) için uygulanarak daha pratik ve esnek bir şekilde gerçekleştirilmesi sağlanmıştır. Bu model aktör, nesne ve etiketten oluşur. Literatürde sadece okuma veya sadece yazma işlemleri ayrı etiket kullanılarak gerçekleştirilmiştir. Aynı anda tüm işlemler için veri güvenliğini sağlayacak bir yapı geliştirilmemiştir. Bizim çalışmamızda ise nesne üzerinde gerçekleştirilen tüm işlemler için tek etiket kullanılır. Tek etikete bakılarak hangi işlem ile aktörler arasında nasıl bir yetkilendirme ve erişim denetimi yapılacağı gösterilir. Böylelikle literatüde gerçekleştirilen çalışmaların aksine dağıtık veritabanında gerçekleştirilen tüm işlemler için veri gizliliği, veri bütünlüğü ve veri tutarlılığı sağlanmıştır. Ayrıca her aktör diğerlerinden bağımsız bir şekilde kendi güvenlik ve gizlilik politikasını belirler. Etiket aracılığıyla, güvenli olmayan ulaşım kanallarında, akış kontrolü, sistemde bulunan tüm aktörlerin veri gizliliğini sağlar. Veri nesnesi, güvenli olmayan aktör ve ortamlarda güvenli bir şekilde yayılır ve paylaşılır.