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In this paper we present a number of measures that compare rankings of search engine results. We apply these measures to five queries that were monitored daily for two periods of about 21 days each. Rankings of the different search engines (Google, Yahoo and Teoma for text searches and Google, Yahoo and Picsearch for image searches) are compared on a daily(More)
Incomplete relations are relations which contain null values, whose meaning is \value is at present unknown". Such relations give rise to two types of functional dependency (FD). The rst type, called the strong FD (SFD), is satissed in an incomplete relation if for all possible worlds of this relation the FD is satissed in the standard way. The second type,(More)
XML has already become the de facto standard for specifying and exchanging data on the Web. However, XML is by nature verbose and thus XML documents are usually large in size, a factor that hinders its practical usage, since it substantially increases the costs of storing, processing, and exchanging data. In order to tackle this problem, many XML-specific(More)
ÐFunctional dependencies (FDs) and inclusion dependencies (INDs) are the most fundamental integrity constraints that arise in practice in relational databases. In this paper, we address the issue of normalization in the presence of FDs and INDs and, in particular, the semantic justification for Inclusion Dependency Normal Form (IDNF), a normal form which(More)
Three recent trends in database research are object-oriented and deductive databases and graph-based user interfaces. We draw these trends together in a data model we call the Hypernode Model. The single data structure of this model is the <italic>hypernode</italic>, a graph whose nodes can themselves be graphs. Hypernodes are typed, and types, too, are(More)
When writing can change your life, when writing can enrich you by offering much money, why don't you try it? Are you still very confused of where getting the ideas? Do you still have no idea with what you are going to write? Now, you will need reading. A good writer is a good reader at once. You can define how you write depending on what books to read. This(More)