Web Portal for Professional Financial Services

The financial services industry offers great opportunities both for the investors and for the companies providing services to the investors. Most of the existing Web sites offer similar services such as stock/index/options quotes, markets overview, most active issues, etc. On other side, there are various tools for technical analysis, charting, and stocks screening. The paper presents a newly developed Web portal for Professional Financial Services called MFinance that offers for the retail investors the services mentioned over. It provides a detailed explanation of the business cases and the essential functionalities of the portal and the way of their realization based on Java server-side technologies. Special attention is dedicated to the definition and evaluation of trading strategies and to stock screening based on these trading strategies

Pengendalian Konkurensi Pada Transaksi Tersarang Menggunakan Model Hybrid

Pengendalian konkurensi untuk mengakses basis data pada umumnya menggunakan dua model pendekatan yaitu optimistik dan pesimistik. Penelitian ini bertujuan mengembangkan model hybrid untuk pengendalian konkurensi yang diimplementasi kan pada transaksi tersarang. transaksi yang berasal dari pohon berbeda akan ditangani oleh model optimistik, sedangkan transaksi yang berasal dari pohon yang sama ditangani model pesimistik sebagai transaksi tunggal. Metodologi pengujian hasil penelitian, dilakukan secara simulasi pada sistem komputer client-server, dengan membandingkan ketiga model diatas. Pengujian ini menggunakan parameter waktu tanggap, persentase kegagalan, dan throughput. Berdasarkan hasil pengujian menunjukkan bahwa waktu tanggap model hybrid, optimistik murni, dan pesimistik murni berturut-turut adalah 655,80 milidetik,798,89 milidetik dan 1.478,75 milidetik. Persentase dari kegagalan pada moel hybrid, optimistik murni, dan pesimistik murni berturut-turut adalah 22,53%, 35,28% dan 31,53%. Selanjutnya throughput dari model hybrid, optimistik murni, dan pesimistik murni berturut-turut adalah 60,13%, 44,15%, dan 28,25%. Penelitian ini dapat disimpulkan bahwa model hybrid telah dapat menunjukkan kinerja pengendalian konkurensi yang lebih baik dibandingkan dengan model optimistik maupun pesimistik murni, khususnya pada transaksi tersarang. Kata-kata Kunci : basis data, waktu tanggap, persentase kegagalan, throughput, optimistik murni, pesimistik murni, hybri

Transactional concurrency control for resource constrained applications

PhD ThesisTransactions have long been used as a mechanism for ensuring the consistency of databases. Databases, and associated transactional approaches, have always been an active area of research as different application domains and computing architectures have placed ever more elaborate requirements on shared data access. As transactions typically provide consistency at the expense of timeliness (abort/retry) and resource (duplicate shared data and locking), there has been substantial efforts to limit these two aspects of transactions while still satisfying application requirements. In environments where clients are geographically distant from a database the consistency/performance trade-off becomes acute as any retrieval of data over a network is not only expensive, but relatively slow compared to co-located client/database systems. Furthermore, for battery powered clients the increased overhead of transactions can also be viewed as a significant power overhead. However, for all their drawbacks transactions do provide the data consistency that is a requirement for many application types. In this Thesis we explore the solution space related to timely transactional systems for remote clients and centralised databases with a focus on providing a solution, that, when compared to other's work in this domain: (a) maintains consistency; (b) lowers latency; (c) improves throughput. To achieve this we revisit a technique first developed to decrease disk access times via local caching of state (for aborted transactions) to tackle the problems prevalent in real-time databases. We demonstrate that such a technique (rerun) allows a significant change in the typical structure of a transaction (one never before considered, even in rerun systems). Such a change itself brings significant performance success not only in the traditional rerun local database solution space, but also in the distributed solution space. A byproduct of our improvements also, one can argue, brings about a "greener" solution as less time coupled with improved throughput affords improved battery life for mobile devices

Core Technologies for Native XML Database Management Systems

This work investigates the core technologies required to build Database Management Systems (DBMSs) for large collections of XML documents. We call such systems XML Base Management Systems (XBMSs). We identify requirements, and analyze how they can be met using a conventional DBMS. Our conclusion is that an XML support layer on top of an existing conventional DBMS does not address the requirements for XBMSs. Hence, we built a Native XBMS, called Natix. Natix has been developed completely from scratch, incorporating optimizations for high-performance XML processing in those places where they are most effective