Abstract. We define a formal contract language along with subcontract and compliance relations. We then extrapolate contracts out of processes, that are a recursion-free fragment of ccs. We finally demonstrate that a client completes its interactions with a service provided the corresponding contracts comply. Our contract language may be used as a foundation of Web services technologies, such as wsdl and wscl. 1

ABSTRACT The event-driven programming style is pervasive as an efficient method for interacting with the environment. Unfortunately, the event-driven style severely complicates program maintenance and understanding, as it requires each logical flow of control to be fragmented across multiple independent callbacks. We propose tasks as a new programming model for organizing event-driven programs. Tasks are a variant of cooperative multi-threading and allow each logical control flow to be modularized in the traditional manner, including usage of standard control mechanisms like procedures and exceptions. At the same time, by using method annotations, task-based programs can be automatically and modularly translated into efficient event-based code, using a form of continuation passing style (CPS) translation. A linkable scheduler architecture permits tasks to be used in many different contexts. We have instantiated our model as a backward-compatible extension to Java, called TaskJava. We illustrate the benefits of our language through a formalization in an extension to Featherweight Java, and through a case study based on an open-source web server. 1.

The LAML software package makes XML available in Scheme and the functional programming paradigm. The elements of an XML language are mirrored as functions in Scheme. The parameter profiles of the mirror functions is designed to be easily recognizable from an XML point of view, and to make a good fit with Scheme seen as a list processing language. The paper characterizes the mirrors by means of six mirror rules. A series of practical examples illustrate the approach. The XML-in-LAML facility supports systematic mirroring of XML languages to Scheme. The facility consists of a language independent part (common for all XML languages) and language dependent parts, which are generated from XML document type definitions (DTDs).

Abstract. Web sites are evolving into ever more complex distributed applications. But current Web programming tools are not fully adapted to this evolution, and force programmers to worry about too many inessential details. We want to define an alternative programming style better fitted to that kind of applications. To do that, we propose an analysis of Web interaction in order to break it down into very elementary notions, based on semantic criteria instead of technological ones. This allows defining a common vernacular language to describe the concepts of current Web programming tools, but also some other new concepts. This results in a significant gain of expressiveness. The understanding and separation of these notions also makes it possible to get strong static guarantees, that can help a lot during the development of complex applications. 1

We present in this position paper the foundations of the MIC * model and deployment environment as they have emerged in the last years, relate them to current evolutions on semantic GRID dynamic service generation, as reflected by OGSA/I and, more recently, by WSRF, and propose an integrated view with the previously proposed STROBE model for communicating agents leading to a quite simple yet very promising architecture that may include Human agents in the loop, uninspectable as most artificial agents, yet behaving autonomously by interacting. Modeling Human agents seems to us of high importance in the high level service generation required by complex, semantically rich applications, such as those of e-Learning, e-Science or e-Commerce envisaged in the years to come. 1.

We present in this position paper the foundations of the MIC * model and deployment environment as they have emerged in the last years, relate them to current evolutions on semantic GRID dynamic service generation, as reflected by OGSA/I and, more recently, by WSRF, and propose an integrated view with the previously proposed STROBE model for communicating agents leading to a quite simple yet very promising architecture that may include Human agents in the loop, uninspectable as most artificial agents, yet behaving autonomously by interacting. Modeling Human agents seems to us of high importance in the high level service generation required by complex, semantically rich applications, such as those of e-Learning, e-Science or e-Commerce envisaged in the years to come. 1.

Abstract. The original C10K problem [1] studies how to provide reasonable service to 10, 000 simultaneous clients or HTTP requests using a normal web server. We call the following problem the reverse C10K problem, or RC10K — how to support 10, 000 simultaneous outbound HTTP requests running on a web server. The RC10K problem can be found in scenarios like service orchestrations and server-side mashups. A server-side mashup needs to send several simultaneous HTTP requests to partner services for each inbound request. Many approaches to improving the performance and scalability of HTTP servers can be applied to tackle the original C10K problem. However, whether these approaches can tackle the reverse C10K problem needs to be verified. In this paper, we discuss the RC10K problem for server-side mashups, and propose a design that takes advantage of advanced I/O, multithreading, and eventdriven programming. The results of analysis and experiments show that our design can reduce the resource requirements by almost one order of magnitude with the same performance provided, and it is promising to tackle the RC10K problem.