The 4CaaSt project aims at developing a PaaS framework that enables flexible definition, marketing, deployment and management of Cloud-based services and applications. The major innovations proposed by 4CaaSt are the blueprint and its lifecycle management, a one stop shop for Cloud services and a PaaS level resource management featuring elasticity. 4CaaSt also provides a portfolio of ready to use Cloud native services and Cloud-aware immigrant technologies.

Marketplaces for cloud services, referred to as electronic marketplaces (eMPs), have been introduced for a number of purposes, including comparability and transparency of service offerings. Since the complexity of services and their provisioning is increasing, eMPs need to handle the dynamic and automated creation of composite services, i.e. services which are yielded in part by using third-party services available on the marketplace. To meet this requirement, eMPs need a standardized machine readable description of service offerings. This paper presents an approach to define price models for services traded on eMPs, using a subset of the Unified Service Description Language (USDL). To enable composite service pricing, this paper introduces an approach on the aggregation of several price models into one price model and analyses the time complexity of the price aggregation algorithm presented.

Modeling the business processes of an organization for the purpose of documentation, optimization, or execution is a vital application in many domains. However, a general issue with existing process modeling (PM) tools is a lack of modeling methodologies for non-IT savvy business users (BUs). Instead, PM is usually performed by specially trained experts that then need to acquire the specific process knowledge from the BUs for modeling, resulting in costly and error-prone PM. Instead, we propose to allow BUs to perform modeling tasks directly by an appropriate user-friendly PM approach. We present our research on End User Development (EUD) for PM aimed at improving the ability of BUs to effectively modify process models according to their individual needs. Our EUD technique is based on a step-by-step instruction design (or wizard) pattern, which has been judged suitable for the considered users. The approach specifically considers how the knowledge of IT experts can be integrated in the development of a tool for supporting PM as these experts know how PM activities are performed and what information is required to support BUs in performing those activities. We have developed a wizard prototype for PM and present first evaluation results.

Recording systems and media servers for networked audio and video streams have become an important part of today's Internet. In contrast to this, only a few recording and playback solutions currently exist for the data streams of interactive media applications (e.g., shared whiteboards and distributed virtual environments). So far these solutions are application-specific: individual algorithms and implementations are required for each application that is to be recorded. In this paper, we are proposing generic algorithms for the recording and playback of interactive media streams. These algorithms are based on a common model for the class of interactive media. They enable full random access to recordings by initializing the replaying applications with the required state information (e.g., the current slide in a recorded presentation). We have implemented these algorithms in the Interactive Media on Demand (IMoD) system. In order to interpret the semantics of an interactive media stream, the system requires that the Real-Time Application-Level Protocol for Distributed Interactive Media (RTP/I) protocol is used for the framing of the transmitted data. Any application using RTP/I can be recorded directly using the system without any modification. Interactive media streams not using RTP/I can be recorded using the generic recording algorithms. However, they require an adaptation of the system so that it is able to extract a minimal set of information from the application-level protocol of these streams. In addition to the generic recording algorithms, we present the architecture and major design considerations of the system and discuss the experiences gained from recording different interactive media applications.

In this paper, we investigate how consistency can be established for replicated applications changing their state in reaction to user-initiated operations as well as the passing of time. Typical examples of these applications are networked computer games and distributed virtual environments. We give a formal definition of the terms consistency and correctness for this application class. Based on these definitions, it is shown that an important tradeoff relationship exists between the responsiveness of the application and the appearance of short-term inconsistencies. We propose to exploit the knowledge of this tradeoff by voluntarily decreasing the responsiveness of the application in order to eliminate short-term inconsistencies. This concept is called local-lag. Furthermore, a timewarp scheme is presented that complements local-lag by guaranteeing consistency and correctness for replicated continuous applications. The computational complexity of the timewarp algorithm is determined in theory and practice by examining a simple networked computer game. The timewarp scheme is then compared to the well-known dead-reckoning approach. It is shown that the choice between both schemes is application-dependent.

We describe a new collaborative technology that is mid-way between the informality of email and the formality of shared workspaces. Email and other ad hoc collaboration systems are typically lightweight and flexible, but build up an unmanageable clutter of copied objects. At the other extreme, shared workspaces provide formal, structured collaboration, but are too heavyweight for users to set up. To bridge this gap between the ad hoc and formal, this paper introduces the notion of "object-centric sharing", where users collaborate in a lightweight manner but aggregate and organize different types of shared artifacts into semi-structured activities with dynamic membership, hierarchical object relationships, as well as real-time and asynchronous collaboration. We present a working prototype implemented with a replicated peer-to-peer architecture, which we describe in detail, and demonstrate its performance in synchronous and asynchronous modes.

No abstract available.

In this paper we present a generic consistency control service for distributed interactive media, i.e. media which allow a distributed group of users to interact with the medium itself. Consistency control is vital to these media since they typically require that a local copy of the medium's state be maintained by each user's application. Our service helps the applications to keep the local state copies consistent. The main characteristics of this service are as follows: a signicant number of inconsistencies are prevented by using a mechanism called local lag. Inconsistencies that cannot be prevented are repaired by an improved timewarp algorithm that can be executed locally without burdening the network or the applications of other users. Exceptional situations and consistency during late-join situations are supported by a consistent state request mechanism. Moreover, the service also supports the application in detecting intention conicts between the actions of distinct users. The major part of this functionality is based on a media model and the application level protocol for distributed interactive media (RTP/I) and can thus be reused by arbitrary RTP/I-based applications. In order to demonstrate the feasibility of our approach and to evaluate its performance we have integrated the generic consistency service into a shared whiteboard system.

We propose a novel late join algorithm for distributed applications with a fully replicated architecture (e.g. shared whiteboards). The term 'late join algorithm' is used to denote a mechanism that allows a late-coming participant rejoin an ongoing session. Generally, this requires that participants in the session provide the latecomer with the current state of the shared application. We identify the key issues of late join algorithms and propose a set of requirements which a 'good' late join approach should satisfy. Based on these requirements, we evaluate existing late join algorithms and explain why we opted instead to develop a new, advanced late join algorithm for our own shared whiteboard. This late join approach is general enough to be used for arbitrary distributed applications.

In this paper we present a generic late-join service for distributed interactive media, i.e, networked media which involve user interactions. Examples for distributed interactive media are shared whiteboards, networked computer games and distributed virtual environments. The generic late-join service allows a latecomer to join an ongoing session. This requires that the shared state of the medium is transmitted from the old participants of the session to the latecomer in an efficient and scalable way. In order to be generic and useful for a broad range of distributed interactive media, we have implemented the late-join service based on the Real Time Application Level Protocol for Distributed Interactive Media (RTP/I). All applications which employ this protocol can also use the generic late-join service. Furthermore the late-join service can be adapted to the specific needs of a given application by specifying policies for the late-join process. Applications which do use a different application level protocol than RTP/I may still use the concepts presented in this work. However, they will not be able to profit from our RTP/I based implementation.