Henk F. Moed and Gali Halevi have self-archived "The Multidimensional Assessment of Scholarly Research Impact."
Here's an excerpt:
This article introduces the Multidimensional Research Assessment Matrix of scientific output. Its base notion holds that the choice of metrics to be applied in a research assessment process depends upon the unit of assessment, the research dimension to be assessed, and the purposes and policy context of the assessment. An indicator may by highly useful within one assessment process, but less so in another. For instance, publication counts are useful tools to help discriminating between those staff members who are research active, and those who are not, but are of little value if active scientists are to be compared one another according to their research performance. This paper gives a systematic account of the potential usefulness and limitations of a set of 10 important metrics including altmetrics, applied at the level of individual articles, individual researchers, research groups and institutions. It presents a typology of research impact dimensions, and indicates which metrics are the most appropriate to measure each dimension. It introduces the concept of a meta-analysis of the units under assessment in which metrics are not used as tools to evaluate individual units, but to reach policy inferences regarding the objectives and general setup of an assessment process.