Analysis and conception of tuple spaces in the eye of scalability

Applications in the emerging fields of eCommerce and Ubiquitous Computing are composed of heterogenous systems that have been designed separately. Hence, these systems loosely coupled and require a coordination mechanism that is able to gap spatial and temporal remoteness. The use of tuple spaces for data-driven coordination of these systems has been proposed in the past. In addition, applications of eCommerce and Ubiquitous Computing are not bound to a predefined size, so that the underlying coordination mechanism has to be highly scalable. However, it seems to be difficult to conceive a scalable tuple space. This report is an English version of the author\u27s diploma thesis. It comprises the chapter two, three, four, and five. By this means, the design and the implementation of the proposed tuple space is not part of this report

Twenty years of coordination technologies: State-of-the-art and perspectives

Since complexity of inter- and intra-systems interactions is steadily increasing in modern application scenarios (e.g., the IoT), coordination technologies are required to take a crucial step towards maturity. In this paper we look back at the history of the COORDINATION conference in order to shed light on the current status of the coordination technologies there proposed throughout the years, in an attempt to understand success stories, limitations, and possibly reveal the gap between actual technologies, theoretical models, and novel application needs

Behavioural access control in distributed environments

Applications and services in distributed environments are an increasingly important topic. Hence approaches to security issues in such applications are also becoming essential. Crucial information is needed to be protected properly and mechanisms must be developed for this protection. Access control is one of the topics that underline security problems. It concerns assuring that data or resources are accessed by the correct entities. A commonly used access control approach is called access control lists, which is widely applied in most operating systems. However, this approach has some weaknesses with regard to scalability, and so it is not very suitable for distributed environments that usually have variable populations. Capabilities on the other hand offer scalability and adaptability advantages over access control lists. Capabilities are unforgeable tickets that can be propagated between entities, and fit well in distributed environments. But capabilities also have limits due to their simple structure. They grant infinite number of accesses for given types of actions, but are not able to capture sequences and branches of actions, which may be called aspects of behaviours. In this thesis, behaviour control approaches are introduced, through Vistas to Treaties. Vistas can provide explicit access control for each component of objects, and provide primitive control over action sequences. Treaties develop behaviour control further by containing behaviour descriptors which can specify those sequencing, branching and terminating aspects, and hence can provide much finer control over behaviours. Because treaties inherit the scalable attributes of capabilities, they also fit well in distributed environments. An interesting feature in treaty systems is that they allow users to refine the specifications of behaviours and generate new treaties from existing ones. A number of treaty combinator operations are proposed to realize this functionality, and they are shown to be safe with respect to the security of access control. A novel issue created by the treaty approach is identified in the thesis. The new problem is called the duplication problem, which could cause users being able to gain more permissions than they should have by making copies of unprotected treaties. Any treaty systems must provide solutions to this problem. Three models which solve the duplication problem are proposed, with an analysis of their differences, and advantages and disadvantages. Treaties are a general concept and in real cases they can be represented in various ways. There are components in treaties that have given a variety of implementation options, and the developers of services and applications can choose to combine these options to fit their special requirements. This makes treaties more flexible and adaptable. The implementations of concreted treaties and treaty systems are introduced, and these implemented treaties are used to test their behaviour control abilities. Evaluations for different treaty representations are provided to compare their performance. Scalability of treaty systems is also evaluated, showing that treaties are good to be deployed in distributed environments

Functional programming languages in computing clouds: practical and theoretical explorations

Cloud platforms must integrate three pillars: messaging, coordination of workers and data. This research investigates whether functional programming languages have any special merit when it comes to the implementation of cloud computing platforms. This thesis presents the lightweight message queue CMQ and the DSL CWMWL for the coordination of workers that we use as artefact to proof or disproof the special merit of functional programming languages in computing clouds. We have detailed the design and implementation with the broad aim to match the notions and the requirements of computing clouds. Our approach to evaluate these aims is based on evaluation criteria that are based on a series of comprehensive rationales and specifics that allow the FPL Haskell to be thoroughly analysed. We find that Haskell is excellent for use cases that do not require the distribution of the application across the boundaries of (physical or virtual) systems, but not appropriate as a whole for the development of distributed cloud based workloads that require communication with the far side and coordination of decoupled workloads. However, Haskell may be able to qualify as a suitable vehicle in the future with future developments of formal mechanisms that embrace non-determinism in the underlying distributed environments leading to applications that are anti-fragile rather than applications that insist on strict determinism that can only be guaranteed on the local system or via slow blocking communication mechanisms

Safer Tuple Spaces

. The simplicity and elegance of the Linda programming model is based on its single, global, typeless tuple space. However, these virtues come at a cost. First, the tuple space can be an impediment to scalable high performance. Second, the "black box" nature of the tuple space makes it an inherently dangerous data structure, prone to many types of programming errors. Blossom is a C++ version of Linda with extensions. This paper introduces some of the novelties in Blossom, as they pertain to creating "safe" tuple spaces. These new features include multiple strongly typed tuple spaces, field access patterns, tuple space access patterns, and assertions. 1 Introduction The computing literature is replete with programming models for writing parallel programs. Many of them are research prototypes that are good enough for a few academic papers and then quietly disappear. Few models attract sustained interest in the literature, or establish a large user community. Linda [7] is one of the rare..