Ali Alwan

Due to its great benefits over many database applications, skyline queries have received formidable concern in the last decades. Skyline queries attempt to assist users by identifying the set of data items which represents the best results that meet the conditions of a given query. Most of the existing skyline techniques concentrate on identifying skylines over a single relation. However, in distributed databases, the process of skyline queries required accessing multiple relations which might be located at different sites. Consequently , data items from these multiple relations need to be joined and thus transferring these data items from one site to another is unavoidable. Moreover, the previous techniques also assume that the values of dimensions for every data item are presented (complete) which is not always true as some values may be missing. In this paper, we proposed an approach for processing skyline queries in incomplete distributed databases. The approach derives skylines from multiple relations where dominated data items are removed before joining the relations to reduce the processing time and the network cost. The experimental results illustrate that our proposed approach outperforms the previous approaches in terms of processing time and network cost.

Incompleteness of data is a common problem in many databases including web heterogonous databases, multi-relational databases, spatial and temporal databases and data integration. The incompleteness of data introduces challenges in processing queries as providing accurate results that best meet the query conditions over incomplete database is not a trivial task. Several techniques have been proposed to process queries in incomplete database. Some of these techniques retrieve the query results based on the existing values rather than estimating the missing values. Such techniques are undesirable in many cases as the dimensions with missing values might be the important dimensions of the user’s query. Besides, the output is incomplete and might not satisfy the user preferences. In this paper we propose an approach that estimates missing values in skylines to guide users in selecting the most appropriate skylines from the several candidate skylines. The approach utilizes the concept of...

Nowadays in database systems finding the best results that meet the preferences of users is the most important issue. Skyline queries will present the data items that are not being dominated by the other items in a database. Most of the operations assume the database is complete which means there are no missing values in the database dimensions. In reality, databases are not complete especially for multidimensional database. Missing values have a negative effect on finding skyline points. It changes the native of dominance relation, leads to cyclic dominance and unsatisfying the transitivity property of skylines. This problem becomes more severe in dynamic database in which new items are inserted or items are deleted or updated from the database. Besides, most of the works that handled the incomplete issue assumed that items are static. In this paper we propose the new approach which finds the most relevant data items that meet user's preferences for dynamic incomplete databases.

Abstract - Nowadays, many users use web search engines to find and gather information. User faces an increasing amount of various semi-structured information sources. The issue of correlating, integrating and presenting related information to users becomes important. ...

Nowadays in database systems finding the best results that meet the preferences of users is the most important issue. Skyline queries present data items that are not being dominated by the other data items in a database. Most of the approaches assume that the database is complete which means there are no missing values in the database dimensions. In reality, databases are not complete especially databases with multidimensional. Missing values have a negative effect on finding skyline points. It changes the native of dominance relation, leads to cyclic dominance, and unsatisfying the transitivity property of skylines. This problem becomes more severe in dynamic database in which new data items are inserted into the database while existing data items are deleted or updated from the database. Besides, most of the works that handled the incomplete issue assumed that data items are static. In this paper we propose an approach which finds the most relevant data items that meet user's ...

Abstract. This article aims to automate the extraction of information from semi-structured web documents by minimizing the amount of hand coding. Ex-traction of information from the WWW can be used to structure the huge amount of data buried in web documents, so that data ...