The ever more widespread use of the Internet now makes it possible to bring many more persons than hitherto into environmental impact assessment and resulting decision-making processes. Because most at these persons are non-experts, however, it is necessary to provide them with tools that will support their assessments and decision-making efforts. When these tools are directed primarily to the making of judgements they may be described as judgement engines. The need to promote cooperative attitudes among participants in the assessment and judgemental/decision-making process, requires that these tools should promote transparency. Judgemental processes are introduced and related to evaluation processes so as to provide a characterisation of transparency.

This paper gives an overview of the relevant Internet technologies and then takes the reader through the conception and realisation of one client–server component of an Internet-distributed judgement engine for environmental impact assessment. Because this is built upon the MikeImpact judgement engine of the Danish Hydraulic Institute, it is called a Web-MikeImpact. Although possibly of interest to specialists in information and control technologies, this paper is primarily intended as a background for potential users of Web-MikeImpact. It should be used alongside the use of the artefact that it describes, as this is available on http://www.hi.ihe.nl/hi/test/mikeimpact/mikeindex1.htm.