Showing papers on "restrict published in 1995"

Ecotourism: An economic analysis

Abstract: Ecotourism refers to tourists travelling to a nature site because of the amenity and recreational value derived from having contact with some aspect of the natural world. While ecotourism is a rapidly growing phenomenon, very much of this growth is unsustainable. This article reviews why this unsustainability arises and how it can be avoided. The first section sets out an economic model of ecotourism as the utilisation of open access to renewable natural sites. This model is used to demonstrate how open access can lead to both economic and environmental inefficiency. The second section examines management solutions to the open access problem. This involves determining an owner of the site, either the state, or the local community, or a private group. This owner must then choose policy instruments to restrict open access. This involves choosing between price and quantity instruments, deciding how to reduce rent dissipation and determining whether to restrict total numbers of tourists or damage done per tou...

Getting Close to Objects: Object-Focused Programming Environments

Abstract: Current visual programming environments make use of views and tools to present objects. These view-focused environments provide great functionality at the expense of distancing the objects behind the intermediary layers of views and tools. We propose the object-focused model, which attempts to foster the notion that objects themselves are directly available for interaction. Unique, directly manipulable representations of objects make them immediate, and basing functionality on the object rather than on extrinsic tools makes them the primary loci of action. But although immediacy and primacy contribute to the sense of concreteness of the objects, discarding conventional views and tools potentially restrict the functionality of the environment. Fortunately, by being extremely faithful to the notion of concreteness of objects, two principles emerge that allow object-focused environments to match the functionality of view-focused environments. The principle of availability makes functionality of objects accessible across contexts, and the principle of liveliness allows objects to participate in multiple contexts while retaining concreteness. All these elements help make objects seem more real in the objectfocused environment, hopefully lessening some of the cognitive burden of programming by reducing the distance between the programmer’s mental model of objects and the environment’s representation of objects. Programmers can get the sense that the objects on the screen are the objects in the program, and thus can think about working with objects rather than manipulating the environment. 1 INTRODUCTION Visual programming’s attractiveness stems in large part from its immediacy—programmers directly interact with program elements as if they were physical objects. These concrete visualizations of the program on the computer screen shape how programmers visualize the program within their mind, and may give them a foothold from which to think about the program: people find it easier to deal with the concrete than with the abstract. Object-oriented programming languages (even those that rely primarily on textual representations) strive toward the same end by providing objects as the fundamental elements in the program. Objects encapsulate and make concrete the elements of the program, including both the data to be manipulated and the behavior to be applied to them. Again, this paradigm works because most people find it easier to deal with the concrete than with the abstract. Yet while object-oriented programming languages assist the programmer by providing a concrete notion of objects, most programming environments for these languages push the programmer in the opposite direction, back toward the