Many e-commerce web sites such as online book retailers or specialized information hubs such as online movie databases make use of recommendation systems where users are directed to items of interests based on past user interactions. Keyword-based approaches, collaborative and content filtering techniques have been tried and used over the years each having their own shortcomings. While keyword based approaches are naive and do not take content or context into account collaborative and content filtering techniques suffer from biased ratings, first item and first-rater problems. Recent approaches try to incorporate underlying semantic properties of data by employing ontology based usage mining. This thesis aims to design a recommendation system based on ontological data where web pages are seen as objects with attributes and relations. Instead of relying on users&rsquo / content ratings, user sessions are clustered on a iv semantic level to capture different behavioral groups. Since semantic information is used for the clustering distance function, each cluster represents a behavior group instead of simpler data groups. New users are then assigned to individual clusters that best represent their behavior and recommendations are generated accordingly. In this thesis we use the recommendation results as a means for measuring the effectiveness of the clusters we have generated. We have compared the results obtained using the ontological data and the results obtained without using it and shown that semantic integrating semantic knowledge increases both precision and recall.

One of the most crucial decisions when developing a system based on Service Oriented Architecture is to select an appropriate server which will be the ground for building the application. Similar to databases, an application server has significant influence on efficiency, stability, and security of entire system. During the preparation of architecture for system development one has to decide which available application server would be optimal for hosting and maintaining v Web Services in the given case. There are multiple significant criteria that lead to the proper choice. The impact on a decision among other things is type of the physical machine on which the application server is installed, estimated number of simultaneous clients, and sizes of requests and responses between clients and server. The goal for this thesis is to conduct the comparative analysis of the most commonly used application servers using Service Oriented Architecture and to determine which server should be applied in which particular cases. Performance and load tests will be conducted using SoapUI application.

This thesis puts forth a process for ontology driven distributed simulation through a case study. Ontology is regarded as a domain model, including objects, attributes, methods and object relations. The case study involves trajectory simulation. A trajectory simulation is a piece of software that calculates the flight path and other parameters of a munition, such as its orientation and angular rates, from launch to impact. Formal specification of trajectory simulation domain is available as a domain model in the form of an ontology, called Trajectory Simulation ONTology (TSONT). Ontology driven federation development process proposed in this thesis is executed in three steps. The first step is to analyze the TSONT and to create instances of individuals guided by the requirements of the targeted simulation application, called Puma Trajectory Simulation. Puma is the simulation of a ficticious air-to-ground guided bomb. The second step is to create the High Level Architecture(HLA) Federation Object Model (FOM) using Puma Simulation individuals. FOM will include the required object and interaction definitions to enable information exchange among federation members, including the Puma federate and the Exercise Manager federate. Transformation from the ontology to FOM is realized in two ways: manually, and by using a tool called OWL2OMT. The third step is to implement the Trajectory Simulation federation based on the constructed FOM. Thus, the applicability of developing HLA federates and the federation under the guidance of ontology is demonstrated.

Flash Memories have been widely used as a storage media in electronic devices such as USB flash drives, mobile phones and cameras. Flash Memory offers a portable and non-volatile de- sign, which can be carried to everywhere without data loss. It is durable against temperature and humidity. With all these advantages, Flash Memory gets popular day by day. However, Flash Memory has also some disadvantages, such as erase-before restriction and erase limi- tation of each individual block. Erase-before restriction pushes every single writable unit to be erased before an update operation. Another limitation is that every block can be erased up to a fixed number. Flash Translation Layer - FTL is the solution for these disadvantages. Flash Translation Layer is a software module inside the Flash Memory working between the operating system and the memory. FTL tries to reduce these disadvantages of Flash Memory via implementing garbage collector, address mapping scheme, error correcting and many oth- ers. There are various Flash Translation Layer software. Some of them have been reviewed in terms of their advantages and disadvantages. The study aims at designing, implementing and simulating a NAND type FTL algorithm.

In this thesis, effects of some software design patterns on real time software performance will be investigated. In real time systems, performance requirements are critical. Real time system developers usually use functional languages to meet the requirements. Using an object oriented language may be expected to reduce performance. However, if suitable software design patterns are applied carefully, the reduction in performance can be avoided. In this thesis, appropriate real time software performance metrics are selected and used to measure the performance of real time software systems.

The information that World Wide Web (WWW) provides have grown up very rapidly in recent years, which resulted in new approaches for people to reach the information they need. Although web pages and search engines are indeed strong enough for us to reach what we want, it is not an efficient solution to present data and wait people to reach it. Some more creative and beneficial methods had to be developed for decreasing the time to reach the information and increase the quality of the information. Recommendation systems are one of the ways for achieving this purpose. The idea is to design a system that understands the information user wants to obtain from user actions, and to find the information similar to that. Several studies have been done in this field in order to develop a recommendation system which is capable of recommending movies, books, web sites and similar items like that. All of them are based on two main principles, which are collaborative filtering and content based recommendations. Within this thesis work, a recommendation system approach which combines both content based (CB) and collaborative filtering (CF) approaches by capturing the effect of time like purchase time or release time. In addition to this temporal behavior, the influence of demographic information of user on purchasing habits is also examined this system which is called &ldquo / TDRS&rdquo / .

Aspects are units of aspect oriented programming developed for influencing the software behavior. In order to use an aspect confidently in any software, first it should be verified. For verification of an aspect, the mock classes for the original software should be prepared. These mock classes are a model of the aspect environment which the aspect is woven. In this study, considering that there are not enough tools for supporting the aspect oriented programming developers, we have developed a tool for enabling aspect verification and unit testing. The tool enables verification by generating the general environment of the aspect. By this tool the users are ensured to focus on the verification of aspects isolated from woven software.

In this thesis, we present an ontology-based information extraction and retrieval system and its application to soccer domain. In general, we deal with three issues in semantic search, namely, usability, scalability and retrieval performance. We propose a keyword-based semantic retrieval approach. The performance of the system is improved considerably using domain-specific information extraction, inference and rules. Scalability is achieved by adapting a semantic indexing approach. The system is implemented using the state-of-the-art technologies in SemanticWeb and its performance is evaluated against traditional systems as well as the query expansion methods. Furthermore, a detailed evaluation is provided to observe the performance gain due to domain-specific information extraction and inference. Finally, we show how we use semantic indexing to solve simple structural ambiguities.

The majority of organizations make their business processes explicit to improve them. Defining business processes manually and modeling them are two alternatives utilized for this purpose. Meanwhile, organizations have quality management systems which are frequently shaped by frameworks. The most commonly used process improvement frameworks in the IT sector are ITIL, Cobit, CMMI and ISO 9001. These frameworks indicate the necessity of process documentation and ISO 9001 addresses the name &ldquo / Quality Manual&rdquo / for this purpose. In this thesis, an automated tool is developed for quality manual generation from predetermined business process models. In addition, a case study is performed by means of a systematic approach and its results were discussed with the findings of structured interviews. The aim of the study is to reduce the effort and time required for quality manual preparation and merge quality management activities with process modeling by means of process documentation.

Information technology usage has become compulsory for all organizations whether government or private organizations to achieve visibility, compete rivals and execute their missions better. To get desired result from usage of information technology, IT of organization has to be managed well. Up till now, various frameworks are developed to manage it well. Best examples for this kind of frameworks are COBIT and ITIL, containing all processes which can be handled in IT management and becoming widespread through the world. COBIT and ITIL are complementary frameworks rather than competitors. Due to this reason, organizations must implement both of them instead of choosing one of them. In addition to these, ISO/IEC 27001:2005 which focuses on information security management process is a quite famous IT standard in terms of security. This thesis provides organizations to meet requirements of these frameworks/standards which are process based frameworks and standards complementary to each other, with a unique implementation by taking unification of processes in a more simple and understandable way. Consequently, it provides reduction in the duplicate work and prevents inconsistencies that may occur. In addition, including CMMI level two requirements motivate the organization to implement higher maturity level of CMMI. Moreover, this study provides organizations to implement ISO 27001 management structure which establish a foundation for extension to technical structure of it. Besides these, this study provides an alignment of frameworks model and COBIT and ITIL which helps organization to trace ITIL and COBIT simultaneously. Lastly by providing a web based application, there exists foundation for knowledge bank of IT processes in Turkish and profile pages for each organization to manage, trace and reach their own IT processes in a digital environment.