Ohad Barzilay

How do programmers ask and answer questions on the web? (NIER track)

Question and Answer (Q&A) websites, such as Stack Overflow, use social media to facilitate knowledge exchange between programmers and fill archives with millions of entries that contribute to the body of knowledge in software development. Understanding the role of Q&A websites in the documentation landscape will enable us to make recommendations on how individuals and companies can leverage this knowledge effectively. In this paper, we analyze data from Stack Overflow to categorize the kinds of questions that are asked, and to explore which questions are answered well and which ones remain unanswered. Our preliminary findings indicate that Q&A websites are particularly effective at code reviews and conceptual questions. We pose research questions and suggest future work to explore the motivations of programmers that contribute to Q&A websites, and to understand the implications of turning Q&A exchanges into technical mini-blogs through the editing of questions and answers.

Playing Both Sides of the Market: Success and Reciprocity on Crowdfunding Platforms

Crowdfunding platforms constitute two-sided markets, bringing together entrepreneurs and potential backers; this peer-based fundraising schema introduces new dynamics into the fundraising process. We focus on platform agents who play on both sides of the market, supporting the ventures of their fellow entrepreneurs and subsequently raising money for their own venture. Acting on both sides of the market is a peer-economy phenomenon that has not yet received much attention. We find that an entrepreneur’s backing-history has a significant effect on financing outcomes; campaigns initiated by entrepreneurs who have previously supported others have higher success rates, attract more backers and collect more funds. We find evidence that supports the existence of a causal channel from playing both sides of the market to increased crowdfunding success. We also provide evidence as to the existence of reciprocity. Project owners back their backers, when possible, at a rate that is significantly higher than other comparable projects. We estimate the effect of such actions on the performance of crowdfunding campaigns and show that playing both sides of the market is a rewarding strategy.

Melanoma miRNA trafficking controls tumour primary niche formation

Melanoma originates in the epidermis and becomes metastatic after invasion into the dermis. Prior interactions between melanoma cells and dermis are poorly studied. Here, we show that melanoma cells directly affect the formation of the dermal tumour niche by microRNA trafficking before invasion. Melanocytes, cells of melanoma origin, are specialized in releasing pigment vesicles, termed melanosomes. In melanoma in situ, we found melanosome markers in distal fibroblasts before melanoma invasion. The melanosomes carry microRNAs into primary fibroblasts triggering changes, including increased proliferation, migration and pro-inflammatory gene expression, all known features of cancer-associated fibroblasts (CAFs). Specifically, melanosomal microRNA-211 directly targets IGF2R and leads to MAPK signalling activation, which reciprocally encourages melanoma growth. Melanosome release inhibitor prevented CAF formation. Since the first interaction of melanoma cells with blood vessels occurs in the dermis, our data suggest an opportunity to block melanoma invasion by preventing the formation of the dermal tumour niche.

Example overflow: using social media for code recommendation

Modern Q&A websites, such as Stack Overflow, use social media to provide concise answers, and offer rich technical context with quality assessment capabilities. Although some of the answers may include executable code snippets, they are entangled in free text and are not easily extracted. Q&A websites are not designed for such direct code reuse. We present Example Overflow, a code search and recommendation tool which brings together social media and code recommendation systems. Example Overflow enables crowd-sourced software development by utilizing both textual and social information, which accompany source code on the Web. Its browsing mechanism minimizes the context switch associated with other code search tools. In this paper we describe the development of the tool, provide preliminary evaluation, and discuss its contribution to an example centric programming paradigm.

Jose: Aspects for Design by Contract80-89

Design by contract is a practical methodology for evolving code together with its specification. The contract has important methodological implications on the design of the program. In addition, tools that instrument the code to check for contract violations help the development process by catching errors close to their sources. This is complicated by several factors, such as the need to collect preconditions from supertypes. There are two issues involved in the implementation of such a tool: the correct enforcement of the theoretical principles, and the instrumentation of the code. Most previous tools tackle both issues, but have subtle failures in one or the other. This paper describes Jose, a tool for design by contract in Java, which uses AspectJ, an aspect-oriented extension of Java, to instrument the program. This allows us to leverage the expertise of the AspectJ developers in instrumenting Java programs, and concentrate on the correct implementation of the design by-contract principles. This approach has the added benefit that it can be generalized to other object-oriented languages that have aspect-oriented extensions. We describe the design decisions made in the implementation of Jose, and the features of AspectJ that helped or hindered this implementation

Facilitating Crowd Sourced Software Engineering via Stack Overflow

The open source community, as well as numerous technical blogs and community web sites, put online vast quantities of free source code, ranging from snippets to full-blown products. This code embodies the software development community’s domain knowledge, and mirrors the structure of the Internet: it is distributed rather than hierarchical; it is chaotic, incomplete, and inconsistent. StackOverflow.com is a Question and Answer (Q&A) website which uses social media to facilitate knowledge exchange between programmers by mitigating the pitfalls involved in using code from the Internet. Its design nurtures a community of developers, and enables crowd sourced software engineering activities ranging from documentation to providing useful, high quality code snippets to be used in production. In this chapter we review Stack Overflow from three perspectives: (1) its design and its social media characteristics, (2) the role it plays in the software documentation landscape, and (3) the use of Stack Overflow in the context of the example centric programming paradigm.

Characterizing Example Embedding as a software activity

We use an empirical qualitative software engineering research to characterize Example Embedding (EE) as a software activity - a collection of fine grained techniques which together assemble an abstract key notion in software development. This perspective lays the foundations for building an activity catalogue, forming new software practices, affecting the development process and motivating the development of new software tools.

A Multidimensional Software Engineering Course

Software engineering (SE) is a multidimensional field that involves activities in various areas and disciplines, such as computer science, project management, and system engineering. Though modern SE curricula include designated courses that address these various subjects, an advanced summary course that synthesizes them is still missing. Such a course would enable young practitioners to get a comprehensive description of SE, to experience a genuine software development process, and to appreciate the relations and tradeoffs between the various domains of SE. This paper proposes a multidimensional SE course framework aimed at giving SE students just such comprehensive, cross-paradigm, practical, and theoretical experience and background. The course is organized along four axes: a) fundamentals of SE; b) practices and tools; c) productization; and d) technology evolution. Each of these axes, in themselves multifaceted, enables an examination of SE on various scales and from different perspectives; together they create a holistic multidimensional description of SE. The course is evaluated according to accepted criteria highlighting the course scope, pedagogic decisions, and relevance. The authors also describe their experience of teaching the course three times in the Tel Aviv University and the academic college of Tel-Aviv-Yaffo, Israel.

Understanding reuse of software examples: A case study of prejudice in a community of practice

Abstract Context The context of this research is software developers’ perceptions about the use of code examples in professional software development. Objective The primary objective of this paper is to identify the human factors that dominate example usage among professional software developers, and to provide a theory that explains these factors. Method To achieve this goal, we analyzed the perceptions of professional software developers as manifested on LinkedIn online community. We analyzed the data qualitatively using adapted grounded theory research procedures. Results The research yields an initial framework of key factors that dominate professional developers’ perception regarding example usage. We use the theoretical lens of prejudice theory to put these factors in a broader context, and outline initial recommendations to address these factors in professional organizational context. Conclusion The results of this work, in particular the use of qualitative techniques – allowed us to obtain rich insight into key human factors that affect professional software developers, and enrich the body of literature on the issues of reuse. These factors need to be taken into account as part of an organizational reuse strategy.

NANDFS: a flexible flash file system for RAM-constrained systems

NANDFS is a flash file system that exposes a memory-performance tradeoff to system integrators. The file system can be configured to use a large amount of RAM, in which case it delivers excellent performance. In particular, when NANDFS is configured with the same amount of RAM that YAFFS2 uses, the performance of the two file systems is comparable (YAFFS2 is a file system that is widely used in embedded Linux and other embedded environments). But YAFFS2 and other state-of-the-art flash file systems allocate RAM dynamically and do not provide the system builder with a way to limit the amount ofmemory that they allocate. NANDFS, on the other hand, allows the system builder to configure it to use a specific amount of RAM. The performance of NANDFS degrades when the amount of RAM it uses shrinks, but the degradation is graceful, not catastrophic. NANDFS is able to provide this flexibility thanks to a novel data structure that combines a coarsegrained logical-to-physical mapping with a log-structured file system.