Sharks are highly vulnerable to intense and prolonged fishery extraction. This article analyzes the data on shark landings from the artisan fishing fleet on Costa Rica's Pacific coast between 1988 and 1997. The data come from an invoicing system administered by the Costa Rican Fisheries Institute (Instituto Costarricense de la Pesca y Acuacultura, INCOPESCA). Pacific coast shark fishing during ...

The Invoicing case study is a typical business system proposed by Henri Habrias as a common example for a contest on the capacity of particular formal methods to capture requirements from the client. For this, the case study is informally described by half a page of English text. In this report, we use the formal description technique Lotos for requirement capture, formal description and veriic...

This paper presents an initial attempt at a solution to a challenge set by Prof. Henri Habrias to compare the questions raised by di erent methods in the formalization of an informal set of requirements. The notation used is Z, based on set theory and predicate logic, augmented with the schema notation for structuring. The original English language description of what is required is included ve...

The recent sharp appreciation of the Canadian dollar vs. the US dollar poses difficulties for the Canadian economy and reignites the debate as to whether Canada should fix the Canadian dollar to the US dollar by implementing a unilateral peg or forming a monetary union. We compare the welfare of different combinations of monetary and currency policies in an open-economy macroeconomic model that...

It is widely accepted that the US dollar is the central reference currency for international trade pricing in final goods. At the same time, the dollar is the main invoicing currency for primary commodities. This paper links these two observations within a stylized theoretical framework, and shows how this may be used to obtain a quantitative estimate of the gain to the US economy from the use ...