We define mixed fragmentation as a process of simultaneously applying the horizontal and vertical fragmentation on a relation. It can be achieved in one of two ways: by performing horizontal fragmentation followed by vertical fragmentation or by performing vertical fragmentation followed by horizontal fragmentation. The need for mixed fragmentation arises in distributed databases because database users usually access subsets of data which are vertical and horizontal fragments of global relations and there is a need to process queries or transactions that would access these fragments optimally. We present algorithms for generating candidate vertical and horizontal fragmentation schemes and propose a methodology for distributed database design using these fragmentation schemes. When applied together these schemes form a grid. This grid consisting of cells is then merged to form mixed fragments so as to minimize the number of disk accesses required to process the distributed transactions....

In this thesis, we study the problem of representing and manipulating a document to facilitate browsing, editing, string/content searches and document assembly. Two major data models in which documents are represented and stored are : 1. a relational data model, where all text contents in a document are represented in relations, each with several attributes, or 2. a text data model, where documents are represented as contiguous characters, typically interspersed with tags to capture their various logical, semantic, and presentational features and relationships Each approach has its own strengths and limitations. In our work, we study how a hybrid system based on a combined text/relational model can support document management. We describe database design trade-offs involving the appropriate placement of information in the text and relational database components. With an appropriate design, the advantages of both models can be exploited, while the shortcomings of using them individua...

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