The design of ESQL queries Optimizer may be decomposed into three dimensions: (i) the search space which defines the syntactic representation of all relevant aspects of an execution, (ii) the search strategy used to generate an optimal execution plan and (iii) the cost evaluator which calculates the metrics used by the search strategies. In this paper, we investigate issues involved in designin...

Solving sophisticated mathematical problems often requires algebraic algorithms and theorems. However, there are no environments integrating theorem provers and computer algebra systems which consistently provide the inference capabilities of the rst and the powerful arithmetic of the latter systems. As an example for such a mechanized mathematics environment we describe a prototype implementat...

If multiple evaluators analyse the outcomes of a single user test, the agreement between their lists of identified usability problems tends to be limited. This is called the ‘evaluator effect’. In the present paper, three user tests, taken from various domains, are reported and evaluator effects were measured. In all three studies, the evaluator effect proved to be less than in Jacobsen et al.'...

Abstract: A basic principle associated with competent evaluation practice asserts that evaluators should possess the education, abilities, skills, and experience needed to undertake tasks proposed in an evaluation. For those training this also means teaching professional dispositions, because individual’s dispositions (i.e., beliefs values) influence how they will act as professionals. Personal...

We introduce SD3, a trust management system consisting of a high-level policy language, a local policy evaluator, and a certificate retrieval system. A unique feature of SD3 is its certified evaluator: as the evaluator computes the answer to a query, it also computes a proof that the answer follows from the security policy. Before the answer is returned, the proof is passed through a simple che...

The thesis includes this 98-pages summary and appendices containing a paper submitted for journal publication Contents Our 1 contribution to the field of human-computer interaction (HCI) has been centered on evaluating aspects of two usability evaluation methods (UEMs), namely the cognitive walkthrough and the usability test. Chapter 1 in this summary is devoted to an introduction to HCI with p...