We describe a methodology and an authoring/publishing tool for adaptable and/or adaptive Web documents. Our approach is based on intensional logic, the logic of assertions and expressions, which vary over a collection of contexts or possible worlds. In our approach the contexts are sets of values for parameters which specify the current user profile as supplied by the current Web page URL, and the latest user input. The author produces generic (multi-version) source in the form of HTML with extra markup delimiting parts that are sensitive (in various ways) to the parameters. This source (in what we call Intensional Markup Language) is translated into program in a Perl-like language called ISE (Intensional Sequential Evaluator). To generate the appropriately adapted individual pages, the server runs the ISE program in the appropriate context. The program produces HTML that, when displayed in the user's browser, is rendered into the desired adaptation of the requested page. Although this intensional approach was originally designed to work without any explicit user model, we can extend it (and make the documents adaptive as well as adaptable) simply by incorporating a user model that monitors the user and computes some of the profile parameters.
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