Software engineering processes for self-adaptive systems

In this paper, we discuss how for self-adaptive systems some activities that traditionally occur at development-time are moved to run-time. Responsibilities for these activities shift from software engineers to the system itself, causing the traditional boundary between development-time and run-time to blur. As a consequence, we argue how the traditional software engineering process needs to be reconceptualized to distinguish both development-time and run-time activities, and to support designers in taking decisions on how to properly engineer such systems. Furthermore, we identify a number of challenges related to this required reconceptualization, and we propose initial ideas based on process modeling. We use the Software and Systems Process Engineering Meta-Model (SPEM) to specify which activities are meant to be performed off-line and on-line, and also the dependencies between them. The proposed models should capture information about the costs and benefits of shifting activities to run-time, since such models should support software engineers in their decisions when they are engineering self-adaptive systems

Software for continuous game experiments

ConG is software for conducting economic experiments in continuous and discrete time. It allows experimenters with limited programming experience to create a variety of strategic environments featuring rich visual feedback in continuous time and over continuous action spaces, as well as in discrete time or over discrete action spaces. Simple, easily edited input files give the experimenter considerable flexibility in specifying the strategic environment and visual feedback. Source code is modular and allows researchers with programming skills to create novel strategic environments and displays

Essays in Market Dynamics

In Hotelling Revisits the Lab: Equilibration in Continuous and Discrete Time we investigate experimentally the impact of continuous time on a four-player Hotelling location game. The static pure strategy Nash equilibrium (NE) consists of firms paired-up at the first and third quartiles of the linear city. In a repeated simultaneous move (discrete time) treatment, we largely replicate previous findings in which subjects fail to converge to the NE. However, in asynchronous move (continuous time) treatments we see clear convergence towards the NE.In Stability in Competition? Hotelling in Continuous Time we study Hotelling's classic location duopoly model in continuous time with flow payoffs accumulated over time and the price dimension made explicit. In an experimental setting, subjects chose price and location in treatments varying only by the speed of adjustment. We find that the principle of minimum differentiation generally holds, with little distance between subjects' location decisions. Price decisions, however, tend to be volatile, which is arguably consistent with theory. Our data also support recent literature that the ability to respond quickly increases cooperation.Aggregate Dynamics in a Large Virtual Economy: Prices and Real Activity in Team Fortress. Virtual economies are growing as internet technology continues to advance. We analyze a large and complete set of transaction data from the Team Fortress 2 virtual economy, which was designed to allow decentralized barter as the sole exchange institution. A small subset of goods emerges endogenously to act as media of exchange. Taking one of these money goods as numeraire, we generate daily prices for thousands of goods. We then generate macroeconomic indicators, including nominal growth and inflation. We find evidence of a particular sort of nominal rigidity related to the circulation of multiple types of currency goods, and also find some localized asset price bubbles associated with announcements by the game designers

Aggregate Dynamics in a Large Virtual Economy: Prices and Real Activity in Team Fortress 2*

We examine economic activity in a large virtual economy which was designed to allow decentralized barter as the sole exchange institution. We find that a small subset of goods emerges endogenously which act of media of exchange. Our analysis includes estimation of spot exchange rates between these numerous money goods and we develop methods which allows us to price all goods and track inflation. We then calculate nominal growth and its components. We find that per-captita real wealth is an increasing component of nominal growth. Separately, we find evidence of a certain form of nominal price ridigity - the price of an item commonly priced in a particular money good tends to move with the exchange rate of that money good. We also find that announcements made by the economic planners can induce speculation leading to localized asset price bubbles

Emergence of networks and market institutions in a large virtual economy

A complete set of transactions, more than 40 million within a 1.8 year span, allows us to track the evolution of the trader network and the goods network in an on-line trading community. The computer platform was designed to make barter exchange as attractive as possible; money was not part of the design and all players were created equal. Yet, within weeks, several specific goods began to emerge as media of exchange, and not long after that various sorts of specialized traders began to appear. We track their progress using network-theoretic metrics such as node strength, assortativity, betweenness and closeness. By the end of our sample, virtually all trade was money-mediated and market makers played a major role. (author's abstract