What is a Model?

With the recent trend to model driven development a commonly agreed notion of model" becomes a pivotal issue. However, currently there is little consensus about what exactly a model is and what it is not. Furthermore, basic terms such as metamodel" are far from being understood in the same way by all members of the modeling community. This article attempts to start establishing a consensus about generally acceptable terminology. Its main contribution is the distinction between two fundamentally different kinds of models, i.e. type model" versus token model". The recognition of the fundamental difference in these two kinds of models is crucial to avoid misunderstandings and unnecessary disputes among members of the modeling community

What is a model, why people don't trust them, and why they should

It is easier to make one�s way in the world if one has some sort of expectation of the world�s future behaviour. Even when facing a very complex problem, we are rarely in a state of full ignorance: some expectations of system behaviour and the level of risk arising from uncertainty are usually available and it is on the basis of these expectations that most decisions are taken. Humans use models, which are mental or formal representations of reality, to generate these expectations, employing an ability that is shared more or less by all forms of life. Whether it is a tree responding to shortening day length by dropping its leaves and preparing its metabolism for the winter ahead or a naked Pleistocene ape storing food in advance of winter for the same reasons, both are using models. This view leads to two outcomes. The first is that predictions, seen as an expectation of ranges of future behaviours, are not just desirable, but necessary for decision-making. The often-asked question �do models provide reliable predictions?� then shifts to �given a certain problem, what type of models provide the most useful and reliable prediction?� The second outcome is that modelling is no longer a scientist�s activity but is instead a social process. Different types of models can be employed to ensure that all available information is included in model building and that model results are understood, trusted and acted upon

Advanced language modeling approaches, case study: Expert search

This tutorial gives a clear and detailed overview of advanced language modeling approaches and tools, including the use of document priors, translation models, relevance models, parsimonious models and expectation maximization training. Expert search will be used as a case study to explain the consequences of modeling assumptions

Improving teaching and learning for chemical equilibrium and acids and bases in Year 12 chemistry : a thesis submitted in partial fulfilment of the requirements for the degree of MAster of Education at Massey University, Palmerston North, New Zealand

The aims of this action research study were to develop, implement, and test the efficacy of four strategies designed to improve the teaching and learning of chemical equilibrium and acids and bases in year 12 chemistry. The study took place in a New Zealand secondary school, with two year 12 chemistry teachers and fifteen randomly selected students taking part. Semi-structured interviews used to elicit students' pre-teaching mental models of concepts within chemical equilibrium and acids and bases revealed a range of misconceptions and a limited ability to represent the sub-microscopic level of chemistry concepts. Teachers then used information from the interviews to inform the planning of lessons for each topic. The new teaching strategies employed by the teachers centred around Johnstone's three levels of chemistry; using a macroscopic, sub-microscopic, symbolic sequence during teacher explanations of concepts. Particular emphasis was placed on modelling the sub-microscopic level of each concept with magnetic cardboard dots and student role plays. The action research process allows teachers to improve their own understandings and teaching practices through cycles of planning, action, observation and reflection. Although the action research methodology used here was new to both teachers at the start of the study, it provided a useful structure in which to trial the new strategies. Reflection in action research is an opportunity for teachers to reflect on, and evaluate, the effects of their action. This study demonstrates that understanding of concepts within chemical equilibrium and acids and bases is significantly improved if the sub-microscopic level of concepts is represented. For the students in this study, the preferred method of representing the sub-microscopic level was with cardboard dots rather than student role plays. Ideally, students themselves need to practise representing the sub-microscopic level with cardboard dots or other concrete models if they are to gain better understanding of the sub-microscopic level

DGD Gallery: Storage, sharing, and publication of digital research data

We describe a project, called the "Discretization in Geometry and Dynamics Gallery", or DGD Gallery for short, whose goal is to store geometric data and to make it publicly available. The DGD Gallery offers an online web service for the storage, sharing, and publication of digital research data.Comment: 19 pages, 8 figures, to appear in "Advances in Discrete Differential Geometry", ed. A. I. Bobenko, Springer, 201