In this paper, we discuss a scaling approach to business fluctuations. Our starting point consists in recognizing that concepts and methods derived from physics have allowed economists to (re)discover a set of stylized facts which have to be satisfactorily accounted for in their models. Standard macroeconomics, based on a reductionist approach centered on the representative agent, is definitely badly equipped for this task. On the contrary, we show that a simple financial fragility agent-based model, based on complex interactions of heterogeneous agents, is able to replicate a large number of scaling type stylized facts with a remarkable high degree of statistical precision.

a b s t r a c tIn this paper we analyze the Ancona wholesale fish market (MERITAN) where transactions take place in three simultaneous Dutch auctions. Our objective is to characterize the behavior of market participants and, in particular, that of buyers in such a market structure. Our analysis shows that buyer-seller relationships are less important than in a pairwise bargaining market such as the Marseille Fish market but that a significant amount of "loyalty" is still present under the auction mechanism. We provide an explanation of the "declining price paradox" for the fish market of Ancona by linking the rule used by the buyers to set their bid to the relationship between the variation in the price of the last transactions in the day and the quantity of fish available on that day. In fact, the average price tends to increase for the last transactions on days characterized by a limited supply of fish.

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Grid computing has recently become an important paradigm for managing computationally demanding applications, composed of a collection of services. The dynamic discovery of services, and the selection of a particular service instance providing the best value out of the discovered alternatives, poses a complex multi-attribute n:m allocation decision problem, which is often solved using a centralized resource broker. To manage complexity, this article proposes a two-layer architecture for service discovery in such Application Layer Networks (ALN). The first layer consists of a service market in which complex services are translated to a set of basic services, which are distinguished by price and availability. The second layer provides an allocation of services to appropriate resources in order to enact the specified services. This framework comprises the foundations for a later comparison of centralized and decentralized market mechanisms for allocation of services and resources in ALNs and Grids.