Many modern programs provide operating system-style services to extension modules. A Web server, for instance, behaves like a simple OS kernel. It invokes programs that dynamically generate Web pages and manages their resource consumption. Most Web servers, however, rely on conventional operating systems to provide these services. As a result, the solutions are inefficient, and impose a serious overhead on the programmer of dynamic extensions. In this paper, we show that a Web server implemented in a suitably extended high-level programming language overcomes all these problems. First, building a server in such a language is straightforward. Second, the server delivers static content at performance levels comparable to a conventional server. Third, the Web server delivers dynamic content at a much higher rate than a conventional server, which is important because a significant portion of Web content is now dynamically generated. Finally, the server provides programming mech...

The construction of interactive server-side Web applications differs substantially from the construction of traditional interactive programs. In contrast, existing Web programming paradigms force programmers to save and restore control state between user interactions. We present an automated transformation that converts traditional interactive programs into standard CGI programs. This enables reuse of existing software development methodologies. Furthermore, an adaptation of existing programming environments supports the development of Web programs. 1 Designing Web Programs The need for generating Web information on demand is obvious. One page may need the current time and date; another page may include results from a database query; a third page may display the current status of the server. Since such programs compute small amounts of information and produce not much more than a single Web page, people call them scripts. Following a long-standing tradition in computing, Web scripti...

Programmers confront a minefield when they design interactive Web programs. Web interactions take place via Web browsers. With browsers, consumers can whimsically navigate among the various stages of a dialog and can thus confuse the most sophisticated corporate Web sites. In turn, Web services can fault in frustrating and inexplicable ways. The quickening transition from Web scripts to Web services lends these problems immediacy.

Abstract. In this paper we present the iData Toolkit. It allows programmers to create interactive, dynamic web applications with state on a high level of abstraction. The key element of this toolkit is the iData element. An iData element can be regarded as a self-contained object that stores values of a specified type. Generic programming techniques enable the automatic generation of HTML-forms from these types. These forms can be plugged into the web application. The iData elements can be interconnected. Complicated form dependencies can be defined in a pure functional, type safe, declarative programming style. This liberates the programmer from lots of low-level HTML programming and form handling. We illustrate the descriptive power of the toolkit by means of a small, yet complicated example: a project administration. The iData Toolkit is an excellent demonstration of the expressive power of modern generic (poly-typical) programming techniques.

In this paper we introduce the iTask system: a set of combinators to specify work flows in a pure functional language at a very high level of abstraction. Work flow systems are automated systems in which tasks are coordinated that have to be executed by humans and computers. The combinators that we propose support work flow patterns commonly found in commercial work flow systems. Compared with most of these commercial systems, the iTask system offers several advantages: tasks are statically typed, tasks can be higher order, the combinators are fully compositional, dynamic and recursive work flows can be specified, and last but not least, the specification is used to generate an executable web-based multi-user work flow application. With the iTask system, useful work flows can be defined which cannot be expressed in other systems: work can be interrupted and subsequently directed to other workers for further processing. The implementation is special as well. It is based on the Clean iData toolkit which makes it possible to create fully dynamic, interactive, thin client web applications. Thanks to the generic programming techniques used in the iData toolkit, the programming effort is reduced significantly: state handling, form rendering, user interaction, and storage management is handled automatically. The iTask system allows a task to be regarded as a special kind of persistent redex being reduced by the application user via task completion. The combinators control the order in which these redexes are made available to the application user. The system rewrites the persistent task redexes in a similar way as functions are rewritten in lazy functional languages.

Abstract. The goal of domain-specific languages (DSLs) is to increase the productivity of software engineers by abstracting from low-level boilerplate code. Introduction of DSLs in the software development process requires a smooth workflow for the production of DSLs themselves. This requires technology for designing and implementing DSLs, but also a methodology for using that technology. That is, a collection of guidelines, design patterns, and reusable DSL components that show developers how

Multimodal interfaces are becoming increasingly ubiquitous with the advent of mobile devices, accessibility considerations, and novel software technologies that combine diverse interaction media. In addition to improving access and delivery capabilities, such interfaces enable flexible and personalized dialogs with websites, much like a conversation between humans. In this paper, we present a software framework for multimodal web interaction management that supports mixed-initiative dialogs between users and websites. A mixed-initiative dialog is one where the user and the website take turns changing the flow of interaction. The framework supports the functional specification and realization of such dialogs using staging transformations -- a theory for representing and reasoning about dialogs based on partial input. It supports multiple interaction interfaces, and offers sessioning, caching, and co-ordination functions through the use of an interaction manager. Two case studies are presented to illustrate the promise of this approach.

Abstract. The iData Toolkit is a toolkit that allows programmers to create interactive, type-safe, dynamic web applications with state on a high level of abstraction. The key element of this toolkit is the iData element. An iData element is a form that is generated automatically from a type definition and that can be plugged in in the web page of a web application. In this paper we show how this automatic generation of forms has been implemented. The technique relies essentially on generic programming. It has resulted in a concise and flexible implementation. The kernel of the implementation can be reused for any graphical package. The iData Toolkit is an excellent demonstration of the expressive power of modern generic (poly-typical) programming techniques. 1

Abstract. Conference paper submission and reviewing is an increasingly electronic activity.Paper authors and program committee members expect to be able to use software, especially with Web interfaces, to simplify and even automate many activities.Building interactive Web sites is a prime target of opportunity for sophisticated declarative programming languages.This paper describes the plt Scheme application Continue, which automates many conference paper management tasks.

Our thesis is that programming web applications with continuations is superior to the current page-centric technology. A continuation is a program-level manageable value representing the rest of the computation of the program. "What to do next" is precisely what has to be explicitly encoded in order to program non trivial web interactions. Continuations allow web applications to be written in direct style that is, as a single program that displays forms and reads form submission since continuations automatically capture everything (control point, lexical bindings, etc.) that is needed to resume the computation. Programming is therefore safer, easier and more re-usable. 1