Effort estimation of FLOSS projects: A study of the Linux kernel

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 SpringerEmpirical research on Free/Libre/Open Source Software (FLOSS) has shown that developers tend to cluster around two main roles: “core” contributors differ from “peripheral” developers in terms of a larger number of responsibilities and a higher productivity pattern. A further, cross-cutting characterization of developers could be achieved by associating developers with “time slots”, and different patterns of activity and effort could be associated to such slots. Such analysis, if replicated, could be used not only to compare different FLOSS communities, and to evaluate their stability and maturity, but also to determine within projects, how the effort is distributed in a given period, and to estimate future needs with respect to key points in the software life-cycle (e.g., major releases). This study analyses the activity patterns within the Linux kernel project, at first focusing on the overall distribution of effort and activity within weeks and days; then, dividing each day into three 8-hour time slots, and focusing on effort and activity around major releases. Such analyses have the objective of evaluating effort, productivity and types of activity globally and around major releases. They enable a comparison of these releases and patterns of effort and activities with traditional software products and processes, and in turn, the identification of company-driven projects (i.e., working mainly during office hours) among FLOSS endeavors. The results of this research show that, overall, the effort within the Linux kernel community is constant (albeit at different levels) throughout the week, signalling the need of updated estimation models, different from those used in traditional 9am–5pm, Monday to Friday commercial companies. It also becomes evident that the activity before a release is vastly different from after a release, and that the changes show an increase in code complexity in specific time slots (notably in the late night hours), which will later require additional maintenance efforts

Die Evolution einer Standardarchitektur für Betriebliche Informationssysteme

Echterhoff D, Grasmugg S, Mersch S, Mönckemeyer M, Spitta T, Wrede S. Die Evolution einer Standardarchitektur für Betriebliche Informationssysteme. In: Spitta T, Borchers J, Sneed HM, eds. Software-Management 2002. LNI. Vol P-23. Bonn: GI e.V.; 2002: 131-142.The paper outlines the history of a standard architecture for small and medium sized administrative systems. It has been developped 1985 in the Schering AG / Berlin, and applied in several firms over more than 15 years. Some of the about 150 applications, developped and maintained by more than 100 programmers, are still in operation. In 1999 a revision of the architecture and a new implementation in Java was started. The latest version is a four-level-architecture for distributed systems with a browser as user interface. Aside architectural considerations we discuss some of our design and implementation experiences with java

The shape and erosion of pebbles

The shapes of flat pebbles may be characterized in terms of the statistical distribution of curvatures measured along their contours. We illustrate this new method for clay pebbles eroded in a controlled laboratory apparatus, and also for naturally-occurring rip-up clasts formed and eroded in the Mont St.-Michel bay. We find that the curvature distribution allows finer discrimination than traditional measures of aspect ratios. Furthermore, it connects to the microscopic action of erosion processes that are typically faster at protruding regions of high curvature. We discuss in detail how the curvature may be reliable deduced from digital photographs.Comment: 10 pages, 11 figure

Human cognition of complex thought patterns

How much is our perception of the present determined by our experience of the past

Effects of the green alga Dictyosphaeria ocellata on its surrounding bacterial community

Marine macroalgae are widespread throughout the world’s oceans. They are important primary producers and have been used for millennia as food products for humans. The health and ecology of these organisms are greatly affected by the bacterial communities surrounding them. Because bacteria are so abundant in the oceans, as many as 2.5 x 108 bacterial cells per milliliter of seawater, it is likely that macroalgae have evolved mechanisms to regulate the composition of the bacterial community surrounding them. In fact, recent studies indicate that a certain degree of host specificity exists among bacterial communities on the surface of algae. In addition, it has been known for some time that algae produce compounds with bacteriostatic or bacteriolytic properties. However, a good understanding of the ecological roles of these compounds has yet to be established. In order to better understand the effects of macroalgae on their surrounding bacterial community, I performed a series of field and laboratory experiments using a green siphonous alga, Dictyosphaeria ocellata, as a model organism. The results presented here indicate that D. ocellata regulates the composition of the bacterial community on its surface and in the closely surrounding seawater. Furthermore, that the alga produces organic compounds that are involved in the bacterial community regulation

Estimating survival in patients with gastrointestinal cancers and brain metastases: An update of the graded prognostic assessment for gastrointestinal cancers (GI-GPA).

BackgroundPatients with gastrointestinal cancers and brain metastases (BM) represent a unique and heterogeneous population. Our group previously published the Diagnosis-Specific Graded Prognostic Assessment (DS-GPA) for patients with GI cancers (GI-GPA) (1985-2007, n = 209). The purpose of this study is to update the GI-GPA based on a larger contemporary database.MethodsAn IRB-approved consortium database analysis was performed using a multi-institutional (18), multi-national (3) cohort of 792 patients with gastrointestinal (GI) cancers, with newly-diagnosed BM diagnosed between 1/1/2006 and 12/31/2017. Survival was measured from date of first treatment for BM. Multiple Cox regression was used to select and weight prognostic factors in proportion to their hazard ratios. These factors were incorporated into the updated GI-GPA.ResultsMedian survival (MS) varied widely by primary site and other prognostic factors. Four significant factors (KPS, age, extracranial metastases and number of BM) were used to formulate the updated GI-GPA. Overall MS for this cohort remains poor; 8 months. MS by GPA was 3, 7, 11 and 17 months for GPA 0-1, 1.5-2, 2.5-3.0 and 3.5-4.0, respectively. >30% present in the worst prognostic group (GI-GPA of ≤1.0).ConclusionsBrain metastases are not uncommon in GI cancer patients and MS varies widely among them. This updated GI-GPA index improves our ability to estimate survival for these patients and will be useful for therapy selection, end-of-life decision-making and stratification for future clinical trials. A user-friendly, free, on-line app to calculate the GPA score and estimate survival for an individual patient is available at brainmetgpa.com

What is in a pebble shape?

We propose to characterize the shapes of flat pebbles in terms of the statistical distribution of curvatures measured along the pebble contour. This is demonstrated for the erosion of clay pebbles in a controlled laboratory apparatus. Photographs at various stages of erosion are analyzed, and compared with two models. We find that the curvature distribution complements the usual measurement of aspect ratio, and connects naturally to erosion processes that are typically faster at protruding regions of high curvature.Comment: Phys. Rev. Lett. (to appear