The Request-Response (RR) paradigm is widely used in ubiquitous systems to exchange information in a secure, reliable and timely manner. Nonetheless, there is also an emerging need for adopting the Publish-Subscribe (PubSub) paradigm in this kind of systems, due to the advantages that this paradigm offers in supporting mobility by means of asynchronous, non-blocking and one-to-many message distribution semantics for event notification. This paper analyzes the strengths and weaknesses of both the RR and PubSub paradigms to support communications in ubiquitous systems and proposes an abstract communication model in order to enable their seamless integration. Thus, developers will be focused on communication semantics and the required quality properties, rather than be concerned about specific communication mechanisms. The aim is to provide developers with abstractions intended to decrease the complexity of integrating different communication paradigms commonly needed in ubiquitous systems. The proposal has been applied to implement a middleware and a real home automation system to show its applicability and benefits.

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A key aspect in groupware applications is to provide support for quality collaboration in workgroups. Consequently, some non-functional requirements that are traditionally associated with single-user applications are also becoming demanded for this kind of software. Due to the use of a wide range of ad-hoc methods and development techniques, as well as differences in underlying communication technologies and conceptualization of the applications themselves, there are some important pitfalls in terms of applying methods and techniques to systematically handle non-functional requirements in groupware applications. In this paper, we present an analysis of non functional requirements and specific functional requirements for groupware applications, and propose a framework that serves as a basis for the satisfaction of relevant non-functional requirements in groupware applications: interoperability, integration, usability, extensibility and reusability. The framework consists of a set of mechanisms to support group awareness about the manipulation of multi-user interfaces, a communication and coordination middleware, and a shared workspace encompassing first class concepts present in the system (users, roles, applications, documents, etc.), and their relationships. A case study shows how several groupware applications may be integrated and may interoperate under this approach.

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