Coordinating Asynchronous Actors – from Tuple Spaces to Tweetflows

The coordination of asynchronous actors has always been a major problem in distributed systems and parallel computing. About 20 years ago, David Gelernter and Nicholas Carriero have introduced the coordination language Linda. The most important difference to existing approaches was that they treated the coordination problem seperately from the computation problem. Linda implementations offer the [...]

Bundling Windows for Eucalyptus

Contrary to the commercial version (Eucalyptus Enterprise Edition), the open source version of Eucalyptus 2.0 does not support Windows. According to the Eucalyptus roadmap, Windows will be added in Eucalyptus 3.0. Nevertheless it is possible to run Windows with Eucalyptus 2.0. Hence many step-by-step guides on bundling Windows images for Eucalyptus 2.0 exist, the bundling [...]

Migration of .net Workflows between different hosts

As part of my master thesis on “cloud-based adaptations of service composition hostings” the .net WCF class WorkflowPersistenceService prooved as a promising tool for workflow migrations. class AdaptationPersistenceService: WorkflowPersistenceService { WorkflowAdaptationProxy wap = new WorkflowAdaptationProxy(); protected override void SaveWorkflowInstanceState(Activity rootActivity, bool unlock) { Guid instanceId = (System.Guid)rootActivity.GetValue(Activity.ActivityContextGuidProperty); Console.WriteLine(“Saving Instance {0} “, instanceId); byte[] rootBytes = [...]

Lightweight Service Invocation using Twitter

Lightweight Service Invocation over Twitter can provide benefits through reuse of existing social structures and crowdsourcing opportunities. This article describes an example scenario and the corresponding tweetflow primitives that could be used to control publication, binding, search, invocation, coordination and monitoring of computer-provided as well as human-provided services.

Gossip

Have you heard about gossiping in distributed systems? If not, continue reading. The previous paragraph is already the basic idea of gossip-based systems: One peer has new information and offers it to (a random selection of) other peers. If the contacted peers don’t already know about it, information is exchanged between peers. This is called [...]

Preprocessor for a Data Aggregation Query Language

A Web data aggregation platform which is currently developed at our institute uses a specialized query language (WAQL) to retrieve data from documents and services on the Web. The language is based on XQuery, and provides a set of additional features and language constructs that are useful in the context of Web data aggregation. The [...]

Web-based User Interface for Data Aggregation Platform

This project aims at developing a Web application that serves as a front end (GUI) for a Web services data aggregation platform that is currently being developed at our institute. The platform aggregates (collects, selects and transforms) data from heterogeneous, distributed Web services and documents. A prototype of the GUI already exists and it will [...]