From proprietary to open source—Growing an open source ecosystem

In today's business and software arena, Free/Libre/Open Source Software has emerged as a promising platform for software ecosystems. Following this trend, more and more companies are releasing their proprietary software as open source, forming a software ecosystem of related development projects complemented with a social ecosystem of community members. Since the trend is relatively recent, there are few guidelines on how to create and maintain a sustainable open source ecosystem for a proprietary software. This paper studies the problem of building open source communities for industrial software that was originally developed as closed source. Supporting processes, guidelines and best practices are discussed and illustrated through an industrial case study. The research is paving the road for new directions in growing a thriving open source ecosystem.     

Blind source separation with unknown and dynamically changing number of source signals

The contrast function remains to be an open problem in blind source separation (BSS) when the number of source signals is unknown and/or dynamically changed. The paper studies this problem and proves that the mutual information is still the contrast function for BSS if the mixing matrix is of full column rank. The mutual information reaches its minimum at the separation points, where the random outputs of the BSS system are the scaled and permuted source signals, while the others are zero outputs. Using the property that the transpose of the mixing matrix and a matrix composed by m observed signals have the indentical null space with probability one, a practical method, which can detect the unknown number of source signals n, ulteriorly traces the dynamical change of the sources number with a few of data, is proposed. The effectiveness of the proposed theorey and the developed novel algorithm is verified by adaptive BSS simulations with unknown and dynamically changing number of source signals.     

Corroborating students’ self-reports of source evaluation

Students were asked to report their typical practices with regard to source evaluation using the Credibility Assessment Scale (CAS). Students’ reports were validated against behavioural and cognitive indicators of source evaluation. Specifically, while researching a social science prompt, students’ source use behaviours, related to text evaluation, were logged. Following task completion, students were asked to rank the trustworthiness of the information sources they accessed and to justify their rankings. The criteria students cited for rankings of text trustworthiness were considered to be cognitive-based indicators of source evaluation, and mapped onto CAS items. Limited correspondence was found between students’ reported engagement in verification-related behaviours and either the behaviours manifest during task completion or the criteria for source evaluation cited at post-task. At the same time, a correspondence was found among behavioural and cognitive aspects of source evaluation, within the context of a specific task. This study is unique in directly corroborating self-reported, behavioural, and cognitive measures of source evaluation and examining these within the context of a rich and naturalistic multiple text task. Implications for research and practice are discussed.     

Does open source improve system security?

The current climate of functionality and performance-driven markets has created enormous code bases, which have helped drive growth in the US gross domestic product. However, these code bases have also created an information infrastructure whose vulnerabilities are so striking as to endanger national and economic security. Distributed denial of service attacks have demonstrated that such vulnerabilities can degrade the Internet's aggregate performance, and recurrent virus outbreaks have inflicted substantial repair and recovery costs on businesses worldwide. An attacker could examine public source code to find flaws in a system. So, is source code access a net gain or loss for security? The authors consider this question from several perspectives and tentatively conclude that having source code available should work in favor of system security     

How do open source communities blog?

We report on an exploratory study, which aims at understanding how software communities use blogs compared to conventional development infrastructures. We analyzed the behavior of 1,100 bloggers in four large open source communities, distinguishing between committing bloggers and other community members. We observed that these communities intensively use blogs with one new entry every 8 h. A blog entry includes 14 times more words than a commit message. When analyzing the content of the blogs, we found that committers and others bloggers write about similar topics. Most popular topics in committers’ blogs represent high-level concepts such as features and domain concepts, while source code related topics are discussed in 15% of their posts. Other community members frequently write about community events and conferences as well as configuration and deployment topics. We found that the blogging peak period is usually after the software is released. Moreover, committers are more likely to blog after corrective engineering than after forward engineering and re-engineering activities. Our findings call for a hypothesis-driven research to (a) further understand the role of social media in dissolving the collaboration boundaries between developers and other stakeholders and (b) integrate social media into development processes and tools.     

Sparse representation and blind source separation of ill-posed mixtures

Bofill et al. discussed blind source separation (BSS) of sparse signals in the case of two sensors. However, as Bofill et al. pointed out, this method has some limitation. The potential function they introduced is lack of theoretical basis. Also the method could not be extended to solve the problem in the case of more than three sensors. In this paper, instead of the potential function method, a K-PCA method (combining K-clustering with PCA) is proposed. The new method is easy to be used in the case of more than three sensors. It is easy to be implemented and can provide accurate estimation of mixing matrix. Some criterion is given to check the effect of the mixing matrix A . Some simulations illustrate the availability and accuracy of the method we proposed.     

Open source in Swedish companies: where are we?

Open Source (OS) is a phenomenon of increasing significance for organizations, offering the prospect of effective alternative business solutions and new business opportunities. A number of surveys have been conducted in various countries with the purpose of understanding the state of practice with respect to OS in companies. In this paper we report on a study of the perceptions of OS and the uptake of OS products and development models in Swedish companies. The study used purposeful sampling of companies that have an expressed interest in OS, and the survey was conducted using a set of pre‐prepared questions. Its goal was to investigate the extent to which OS has influenced business thinking, as seen from the standpoint of stakeholders. We found that uptake is much higher than reported in earlier studies, but as with previous studies, activity is still concentrated in small and medium‐sized enterprises (SMEs). There is increased evidence of interest beyond the simple use of OS components at the infrastructure level. Further, a significant proportion of the companies studied are supporting the OS community as well as benefiting from it. Support includes participation in existing projects and the release of new software under OS licenses.     

Natural gradient-based recursive least-squares algorithm for adaptive blind source separation

This paper focuses on the problem of adaptive blind source separation (BSS). First, a recursive least-squares (RLS) whitening algorithm is proposed. By combining it with a natural gradient-based RLS algorithm for nonlinear principle component analysis (PCA), and using reasonable approximations, a novel RLS algorithm which can achieve BSS without additional pre-whitening of the observed mixtures is obtained. Analyses of the equilibrium points show that both of the RLS whitening algorithm and the natural gradient-based RLS algorithm for BSS have the desired convergence properties. It is also proved that the combined new RLS algorithm for BSS is equivariant and has the property of keeping the separating matrix from becoming singular. Finally, the effectiveness of the proposed algorithm is verified by extensive simulation results.     

Optimal source rate control for adapting VBR video over CBR channels

In this paper we discuss the source rate control problem of adapting variable bit-rate （VBR） compressed video over constant bit-rate （CBR） channels. Firstly we formulate it as an optimal control problem of a discrete linear system with state and control constraints. Then we apply the discrete maximum principle to get the optimal solution. Experimental results are given in the end. Compared with traditional algorithms, the proposed algorithm is suitable for the coder with continuous output rates, and can achieve the better solution. Our algorithm can be used in both off-line and on-line coding.     

Astrophysical image separation by blind time–frequency source separation methods

In this paper, two prevalent blind time–frequency (TF) source separation methods in the literature are adapted to astrophysical image mixtures and four algorithms are developed to separate them into their astrophysical components. The components considered in this work are cosmic microwave background (CMB) radiation, galactic dust and synchrotron, among which the CMB component is emphasized. These simulated components mixed via realistic coefficients are subjected to simulated additive, nonstationary Gaussian noise components of realistic power levels, to yield image mixtures on which our orthogonal and nonorthogonal TF algorithms are applied. The developed algorithms are compared with the FastICA algorithm and CMB component is found to be recovered with an improvement reaching to 3.25 decibels from CMB–synchrotron mixtures. The proposed techniques are believed to be generically applicable in separating other types of astrophysical components as well.     

Users’ perception of open source usability: an empirical study

The number of open source software (OSS) users has increased in recent years. No longer are they limited to technically adept software developers. Many believe that the OSS market share could increase tremendously provided OSS had systems that were easier to use. Although examples of good usable open source software exist, it is agreed that OSS can be made more usable. This study presents an empirical investigation into the impact of some key factors on OSS usability from the end users’ point of view. The research model studies and establishes the relationship between the key usability factors from the users’ perspective and OSS usability. A data set of 102 OSS users from 13 open source projects of various sizes was used to study the research model. The results of this study provide empirical evidence by indicating that the highlighted key factors play a significant role in improving OSS usability.     

An empirical investigation into open source web applications’ implementation vulnerabilities

Current web applications have many inherent vulnerabilities; in fact, in 2008, over 63% of all documented vulnerabilities are for web applications. While many approaches have been proposed to address various web application vulnerability issues, there has not been a study to investigate whether these vulnerabilities share any common properties. In this paper, we use an approach similar to the Goal-Question-Metric approach to empirically investigate four questions regarding open source web applications vulnerabilities: What proportion of security vulnerabilities in web applications can be considered as implementation vulnerabilities? Are these vulnerabilities the result of interactions between web applications and external systems? What is the proportion of vulnerable lines of code within a web application? Are implementation vulnerabilities caused by implicit or explicit data flows? The results from the investigation show that implementation vulnerabilities dominate. They are caused through interactions between web applications and external systems. Furthermore, these vulnerabilities only contain explicit data flows, and are limited to relatively small sections of the source code.     

Blow-up analysis in quasilinear reaction–diffusion problems with weighted nonlocal source

In this paper, we consider the blow-up of solutions to a class of quasilinear reaction–diffusion problems

where $\Omega$ is a bounded convex domain in ${\mathbb{R}}^n(n\ge 2)$, weighted nonlocal source satisfies $a\left(x\right)f\left(u(x,t)\right)\le a_1+a_2{\left(u(x,t)\right)}^p{\left({\int }_{\Omega }{\left(u(x,t)\right)}^l\mathrm{d}x\right)}^m,$ and $a_1,a_2,p,l,$ and $m$ are positive constants. By utilizing a differential inequality technique and maximum principles, we establish conditions to guarantee that the solution remains global or blows up in a finite time. Moreover, an upper and a lower bound for blow-up time are derived. Furthermore, two examples are given to illustrate the applications of obtained results.     

Towards multilaterally secure computing platforms—with open source and trusted computing

We present a security architecture for a trustworthy open computing platform that aims at solving a variety of security problems of conventional platforms by an efficient migration of existing operating system components, a Security Software Layer (PERSEUS), and hardware functionalities offered by the Trusted Computing technology. The main goal is to provide multilateral security, e.g., protecting users' privacy while preventing violations of copyrights. Hence the proposed architecture includes a variety of security services such as secure booting, trusted GUI, secure installation/update, and trusted viewer. The design is flexible enough to support a wide range of hardware platforms, i.e., PC, PDA, and embedded systems. The proposed platform shall serve as a basis for implementing a variety of innovative business models and distributed applications with multilateral security.     

Chaotic mixing using source�Csink microfluidic flows in a PDMS chip

We present an active fixed-volume mixer based on the creation of multiple source–sink microfluidic flows in a polydimethylsiloxane (PDMS) chip without the need of external or internal pumps. To do so, four different pressure-controlled actuation chambers are arranged on top of the 5 μl volume of the mixing chamber. After the mixing volume is sealed/fixed by microfluidic valves made using ‘microplumbing technology’, a virtual source–sink pair is created by pressurizing one of the membranes and, at the same time, releasing the pressure of a neighboring one. The pressurized air deforms the thin membrane between the mixing and control chambers and creates microfluidic flows from the squeezed region (source) to the released region (sink) where the PDMS membrane is turned into the initial state. Several schemes of operation of virtual source–sink pairs are studied. In the optimized protocol, mixing is realized in just a sub-second time interval, thanks to the implementation of chaotic advection.     

Lump solutions to the Kadomtsev–Petviashvili I equation with a self-consistent source

Based on symbolic computations, lump solutions to the Kadomtsev–Petviashvili I (KPI) equation with a self-consistent source (KPIESCS) are constructed by using the Hirota bilinear method and an ansatz technique. In contrast with lower-order lump solutions of the Kadomtsev–Petviashvili (KP) equation, the presented lump solutions to the KPIESCS exhibit more diverse nonlinear phenomena. The method used here is more natural and simpler.     

An improved image blind identification based on inconsistency in light source direction

In this study, an improved image blind identification algorithm based on inconsistency in light source direction was proposed. And a new method defined as “neighborhood method” was presented, which was used to calculate surface normal matrix of image in the blind identification algorithm. For an image, there is an error function between its actual light intensity and calculated light intensity, and for different light source models, there are different constraint functions of light. Light source direction which makes both error function and constraint function get the minimum is the one we want to seek. On this basis, according to the error function and the corresponding constraint function, search means and the Hestenes–Powell multiplier method were used in the improved algorithm to calculate the light source direction for local and infinite light source images, respectively. Further, the authenticity of image can be determined by the inconsistency in light source direction of different areas in the image. Experimental results showed that the light source direction of different areas in an image could be calculated accurately, and then the image tampering can be detected effectively by the improved algorithm. Moreover, the performance of the improved algorithm of the proposed blind identification is superior to that of the existing one in terms of detection rate and time complexity.     

Adoption of open source software in software-intensive organizations – A systematic literature review

ContextOpen source software (OSS) is changing the way organizations develop, acquire, use, and commercialize software.ObjectiveThis paper seeks to identify how organizations adopt OSS, classify the literature according to these ways of adopting OSS, and with a focus on software development evaluate the research on adoption of OSS in organizations.MethodBased on the systematic literature review method we reviewed publications from 24 journals and seven conference and workshop proceedings, published between 1998 and 2008. From a population of 24,289 papers, we identified 112 papers that provide empirical evidence on how organizations actually adopt OSS.ResultsWe show that adopting OSS involves more than simply using OSS products. We moreover provide a classification framework consisting of six distinctly different ways in which organizations adopt OSS. This framework is used to illustrate some of the opportunities and challenges organizations meet when approaching OSS, to show that OSS can be adopted successfully in different ways, and to organize and review existing research. We find that existing research on OSS adoption does not sufficiently describe the context of the organizations studied, and it fails to benefit fully from related research fields. While existing research covers a large number of topics, it contains very few closely related studies. To aid this situation, we offer directions for future research.ConclusionThe implications of our findings are twofold. On the one hand, practitioners should embrace the many opportunities OSS offers, but consciously evaluate the consequences of adopting it in their own context. They may use our framework and the success stories provided by the literature in their own evaluations. On the other hand, researchers should align their work, and perform more empirical research on topics that are important to organizations. Our framework may be used to position this research and to describe the context of the organization they are studying.