The ubiquity of Facebook in modern life compels us to study its effects on well-being. We identif... more The ubiquity of Facebook in modern life compels us to study its effects on well-being. We identified a unique sample of Facebook users and non-users who are employed at a security-related organization, where Facebook usage was differentially restricted (even at home) due to an organizational policy change, creating a pseudo-natural experiment. Non-users in our sample are employees who faced an externally imposed circumstantial friction that made them refrain from using Facebook, and hence it is less likely that they chose not to use Facebook because of a-priori personal preferences. This creates unusual conditions that mitigate the inherent selection-bias problem that could occur in estimations of Facebook's impact on social comparison and happiness based simply on who is or is not a user in common circumstances. Performing between-subject analysis, we found significant differences between Facebook users and nonusers at this organization. Given the exogenous assignment to users and non-users, we attribute these differences to the accumulated effect of Facebook usage. Specifically, we infer that Facebook usage increases engagement in social comparison which decreases users' happiness. Social comparison fully mediates the effect of Facebook on happiness, but only for the younger half of our sample and only for those who believe that others have many more positive experiences than they do. Surprisingly, we find that Facebook does not cause users to overestimate the frequency of their friends' positive experiences. Nevertheless, the increased engagement in social comparison adversely affected those who believe that their friends' lives are better than their own. Our findings allude to a new, somewhat more subtle mechanism than suggested by previous studies.
Melanoma originates in the epidermis and becomes metastatic after invasion into the dermis. Prior... more 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.
Design by contract is a practical methodology for evolving code together with its specification. ... more 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 designby-contract ...
Finding Source Code on the Web for Remix and Reuse, 2013
The open source community, as well as numerous technical blogs and community web sites, put onlin... more 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.
Human Aspects of Software Engineering on - HAoSE '10, 2010
ABSTRACT As part of our research on the use of code examples in professional programming, we focu... more ABSTRACT As part of our research on the use of code examples in professional programming, we focus on the developer's awareness and attentiveness to example usage. We identify three types of lack of attentiveness: lack of awareness that causes ...
Context: The context of this research is software developers' perceptions about the use of code e... more 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.
Many digital platforms, regardless of their business domain, follow the common practice of incorp... more Many digital platforms, regardless of their business domain, follow the common practice of incorporating social and community features in order to increase their user engagement and expand their online community. Although this practice is advocated by the literature and clearly makes sense, its implications are not well understood. In this research, we aimed to close this literature gap, providing a theoretical framework and empirical evidence regarding the impact of the online community on platform performance. As a testbed, we studied crowdfunding platforms, that is, designated websites aimed at enabling entrepreneurs to raise money over the Internet. We used comprehensive data collected from Kickstarter, the largest crowdfunding platform established to date. We theorized that online platforms, such as Kickstarter, consist not of a single community but rather a hierarchy of multiple, partially competing communities. These communities vary considerably with respect to the interests of their members, their platform participation patterns, and their impact on platform performance. Our suggested framework incorporates the notion of fluidity of online communities; that is, online users and digital communities evolve and change over time. As the interests of the online user change, so does the membership of her immediate community. The proposed framework allows us to identify such community changes and, consequently, to better identify pivotal members of online communities and predict their lifetime value as potential backers. Empirically, we validated our theory by studying the participation patterns of over 6.3 million Kickstarter users, who have supported more than 150 thousand crowdfunding campaigns over more than 5 years. We demonstrated the growth of the different community types and estimated their different impacts on crowdfunding performance over time. Interestingly, we found that some communities, despite high participation rates, had negative impacts on crowdfunding campaign success. We discuss managerial and practical implications of our theory and findings.
Abstract The evaluation of an advanced software engineering (SE) course is a challenging task tha... more Abstract The evaluation of an advanced software engineering (SE) course is a challenging task that should be addressed as part of the course design. In this paper, we describe an implementation of the reflective practitioner perspective as part of an advanced SE course and introduce its use for feedback purposes. Reflective feedback goes beyond merely using feedback questionnaires.
In the proposed panel we discuss the efforts made by the academy and industry to bring computer s... more In the proposed panel we discuss the efforts made by the academy and industry to bring computer science (CS) to audience that is not exposed to CS education, not represented in the CS workforce or not accessible due to lack in technological solutions.
Abstract Socio-professional websites such as LinkedIn use various mechanisms such as network of c... more Abstract Socio-professional websites such as LinkedIn use various mechanisms such as network of colleagues, groups and discussions to assist their users in maintaining their professional network and keeping up with relevant discussions. Software professionals post hundreds of thousands of comments each week in these group discussions regarding technological and methodological aspects of their work.
Abstract Modern Q&A websites, such as Stack Overflow, use social media to provide concise answers... more Abstract 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.
Abstract Using code examples in professional software development is like teenage sex. Those who ... more Abstract Using code examples in professional software development is like teenage sex. Those who say they do it all the time are probably lying. Although it is natural, those who do it feel guilty. Finally, once they start doing it, they are often not too concerned with safety, they discover that it is going to take a while to get really good at it, and they realize they will have to come up with a bunch of new ways of doing it before they really figure it all out.
ABSTRACT NANDFS is a flash file system that exposes a memory-performance tradeoff to system integ... more ABSTRACT 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).
Abstract We use an empirical qualitative software engineering research to characterize Example Em... more Abstract 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.
Abstract Software engineering (SE) is a multidimensional field that involves activities in variou... more Abstract 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.
Abstract Design by contract is a practical methodology for evolving code together with its specif... more Abstract 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.
The ubiquity of Facebook in modern life compels us to study its effects on well-being. We identif... more The ubiquity of Facebook in modern life compels us to study its effects on well-being. We identified a unique sample of Facebook users and non-users who are employed at a security-related organization, where Facebook usage was differentially restricted (even at home) due to an organizational policy change, creating a pseudo-natural experiment. Non-users in our sample are employees who faced an externally imposed circumstantial friction that made them refrain from using Facebook, and hence it is less likely that they chose not to use Facebook because of a-priori personal preferences. This creates unusual conditions that mitigate the inherent selection-bias problem that could occur in estimations of Facebook's impact on social comparison and happiness based simply on who is or is not a user in common circumstances. Performing between-subject analysis, we found significant differences between Facebook users and nonusers at this organization. Given the exogenous assignment to users and non-users, we attribute these differences to the accumulated effect of Facebook usage. Specifically, we infer that Facebook usage increases engagement in social comparison which decreases users' happiness. Social comparison fully mediates the effect of Facebook on happiness, but only for the younger half of our sample and only for those who believe that others have many more positive experiences than they do. Surprisingly, we find that Facebook does not cause users to overestimate the frequency of their friends' positive experiences. Nevertheless, the increased engagement in social comparison adversely affected those who believe that their friends' lives are better than their own. Our findings allude to a new, somewhat more subtle mechanism than suggested by previous studies.
Melanoma originates in the epidermis and becomes metastatic after invasion into the dermis. Prior... more 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.
Design by contract is a practical methodology for evolving code together with its specification. ... more 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 designby-contract ...
Finding Source Code on the Web for Remix and Reuse, 2013
The open source community, as well as numerous technical blogs and community web sites, put onlin... more 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.
Human Aspects of Software Engineering on - HAoSE '10, 2010
ABSTRACT As part of our research on the use of code examples in professional programming, we focu... more ABSTRACT As part of our research on the use of code examples in professional programming, we focus on the developer's awareness and attentiveness to example usage. We identify three types of lack of attentiveness: lack of awareness that causes ...
Context: The context of this research is software developers' perceptions about the use of code e... more 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.
Many digital platforms, regardless of their business domain, follow the common practice of incorp... more Many digital platforms, regardless of their business domain, follow the common practice of incorporating social and community features in order to increase their user engagement and expand their online community. Although this practice is advocated by the literature and clearly makes sense, its implications are not well understood. In this research, we aimed to close this literature gap, providing a theoretical framework and empirical evidence regarding the impact of the online community on platform performance. As a testbed, we studied crowdfunding platforms, that is, designated websites aimed at enabling entrepreneurs to raise money over the Internet. We used comprehensive data collected from Kickstarter, the largest crowdfunding platform established to date. We theorized that online platforms, such as Kickstarter, consist not of a single community but rather a hierarchy of multiple, partially competing communities. These communities vary considerably with respect to the interests of their members, their platform participation patterns, and their impact on platform performance. Our suggested framework incorporates the notion of fluidity of online communities; that is, online users and digital communities evolve and change over time. As the interests of the online user change, so does the membership of her immediate community. The proposed framework allows us to identify such community changes and, consequently, to better identify pivotal members of online communities and predict their lifetime value as potential backers. Empirically, we validated our theory by studying the participation patterns of over 6.3 million Kickstarter users, who have supported more than 150 thousand crowdfunding campaigns over more than 5 years. We demonstrated the growth of the different community types and estimated their different impacts on crowdfunding performance over time. Interestingly, we found that some communities, despite high participation rates, had negative impacts on crowdfunding campaign success. We discuss managerial and practical implications of our theory and findings.
Abstract The evaluation of an advanced software engineering (SE) course is a challenging task tha... more Abstract The evaluation of an advanced software engineering (SE) course is a challenging task that should be addressed as part of the course design. In this paper, we describe an implementation of the reflective practitioner perspective as part of an advanced SE course and introduce its use for feedback purposes. Reflective feedback goes beyond merely using feedback questionnaires.
In the proposed panel we discuss the efforts made by the academy and industry to bring computer s... more In the proposed panel we discuss the efforts made by the academy and industry to bring computer science (CS) to audience that is not exposed to CS education, not represented in the CS workforce or not accessible due to lack in technological solutions.
Abstract Socio-professional websites such as LinkedIn use various mechanisms such as network of c... more Abstract Socio-professional websites such as LinkedIn use various mechanisms such as network of colleagues, groups and discussions to assist their users in maintaining their professional network and keeping up with relevant discussions. Software professionals post hundreds of thousands of comments each week in these group discussions regarding technological and methodological aspects of their work.
Abstract Modern Q&A websites, such as Stack Overflow, use social media to provide concise answers... more Abstract 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.
Abstract Using code examples in professional software development is like teenage sex. Those who ... more Abstract Using code examples in professional software development is like teenage sex. Those who say they do it all the time are probably lying. Although it is natural, those who do it feel guilty. Finally, once they start doing it, they are often not too concerned with safety, they discover that it is going to take a while to get really good at it, and they realize they will have to come up with a bunch of new ways of doing it before they really figure it all out.
ABSTRACT NANDFS is a flash file system that exposes a memory-performance tradeoff to system integ... more ABSTRACT 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).
Abstract We use an empirical qualitative software engineering research to characterize Example Em... more Abstract 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.
Abstract Software engineering (SE) is a multidimensional field that involves activities in variou... more Abstract 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.
Abstract Design by contract is a practical methodology for evolving code together with its specif... more Abstract 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.
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Papers by Ohad Barzilay