ComSIS has entered the fourth year of its publishing. So far, we have published 45 papers in six regular issues, and one special issue focusing on e-Learning. In the future, we will keep improving the journal quality further. We invite the authors to submit new contributions in the field, as well as contributions for a special issue devoted to programming languages, which is related to the IMCSIT Workshop on Advances in Programming Languages (WAPL '07).

This issue of ComSIS contains two invited papers, two regular research papers, and a book preview. The invited papers come from the distinguished authors, Juan Carlos Augusto and Paul McCullagh, from the University of Ulster, United Kingdom, and Tom Gilb, an independent consultant from Norway. Having a great and multi-disciplinary experience, the authors consider two ever living problems in Computer Science and Software Engineering: how to make computing reach and serve humans, and how to be successful in contracting for software services.

Ambient Intelligence is growing fast as a topic of interest that can allow many areas of research to have a significant beneficial influence on our society. The basic idea is that by enriching an environment with technology, a system can be built to take decisions to benefit the users of that environment based on real-time information gathered and historical data accumulated. Juan Carlos Augusto and Paul McCullagh in their paper "Ambient Intelligence: Concepts and Applications" describe the scope of ambient intelligence (AmI), in particular the relationship in between AmI and related areas, to provide a case study for the Smart Home, and to address other environments where AmI will undoubtedly have future impact. They highlight the technical difficulties and opportunities laying ahead, and possible solutions using software verification. The authors conclude that, still, achieving AmI capabilities is far from easy and certainly is not readily available at the moment. Furthermore, if humans are put at the centre of the system and made more dependant on an AmI system, reliability will be at the level of safety critical systems. Since these systems are autonomous and proactive, predictability and reliability should not be underestimated if we want to have helpful and safe environments where we live and work.

Tom Gilb in his paper "No Cure No Pay: How to Contract for Software Services" addresses the problem of software projects that are 'failures', i.e. cancelled before completion, or 'challenged', i.e. completed and operational, but over-budget, over the time estimate, and/or with fewer features andfunctions than initially specified. The author proposes that a way to avoid software project failure is to refuse to pay for failure. This will motivate software suppliers to make use of already well-known and well-practiced methods for successful IT and software projects. He concludes that there are two key ideas that too many people do not practice. The first is the quantification of the value expected by stakeholders of the system. This gives the basis for payment. The second is to divide all large projects into an incremental series of smaller projects. This means weekly increments (that is roughly 2% of duration time for a large project planned to be completed in about one year) of value delivery. Despite that the paper specifically addresses the software problem, the author says that the ideas most likely apply to the wider systems engineering problem.

In the paper "Developing a New Color Model for Image Analysis and Processing", Rashad J. Rasras, Ibrahiem M. M. El Emary, and Dmitriy E. Skopin present theoretical outcomes and experimental results of a new color model that can be used in modern real time video processing applications. The proposed model is implemented in algorithms and software for image processing. It can be used to solve the problem of true color object identification. Experimental results show that the time spent during the RGI color model conversion may be approximately four times less than the time spent when applying the other conversion models.

Development of human tracking systems is one of the emerging application domains for software engineering and computer science. Fayez Idris, Mazen Abu_Zaher, Rashad J. Rasras, and Ibrahiem M. M. El Emary in their paper "Building an Advanced Invariant Real-Time Human Tracking System" focus on creating an adaptive system for human tracking, which is flexible to handle variations in lighting and/or background, with real-time (indoor or outdoor) performance, using ordinary personal computer without the need for camera calibrations or predefined conditions. While presenting their results, the authors state that human tracking systems play a critical role in many applications such as surveillance and robot applications.

It is the first time in ComSIS that we also have a book preview. This is an opportunity for the authors or reviewers to present new books and their own ideas in the form of a paper, in a non-commercial way. In this issue, Dragan Pleskonjic, Nemanja Macek, Borislav Ðordevic, and Marko Caric in the text "Security of Computer Systems and Networks - Book Preview", present their own book. The book "Security of Computer Systems and Networks" is the result of lecturing experience, research in this area, and also practical experience that authors have in many fields, including but not limited to the architecture and design of security products and software, network projects, consultancy, analysis of issues and problems, and providing solutions to them. The authors hope that this book may make a difference – maybe not a big one, but at least it will make students, engineers, administrators, programmers and other computer users aware of the complexity that security as an evolving process has. In their own preview, the authors conclude that they have really tried not to push readers with maths in cryptography; instead, they tried to tell them that it is an important part of their computer software and to show how it can be used for free.

On behalf of the ComSIS Consortium, let me use this opportunity to give great thanks to the reviewers and all of the authors for their high-quality work, great efforts, and remarkable enthusiasm.

Ivan Luković