This paper introduces the PrairieLearn Question Sharing System (PQSS), which enables instructors to share question generators with other instructors, either as open educational resources or privately. PQSS is integrated into PrairieLearn, an open-source, problem-driven online learning platform. PQSS addresses a critical need for more open-source assessments by making it easier for instructors to share assessments and for instructors to use those assessments. Instructors often do not share questions due to the time it takes to publish them and the lack of recognition for their work. Because it is directly integrated into PrairieLearn, PQSS reduces the aforementioned friction of sharing and using shared questions, and we can report usage statistics to help question authors receive recognition for their work. In this paper, we share design and implementation details of the system, as well as experiences using it to share course content across courses and between universities.

Abstract End-user programmers need programming tools that are easy to learn and use. Development environments for end-users often support one of two visual modalities: block-based programming or data-flow programming. In this work, we discuss differences in how these modalities represent programs, and why existing block-based programming tools are better suited for imperative tasks while data-flow programming better supports nested expressions. We focus on robot programming as an end-user scenario that requires both imperative and expressions-based code in the same program. To study how end-user tools can better support this scenario, we propose two programming system designs: one that changes how blocks represent nested expressions, and one that combines block-based and data-flow programming in the same hybrid environment. We compared these designs in a controlled experiment with 113 end-user participants who solved programming and program comprehension tasks using one of the two environments. Both groups indicated a small preference for the hybrid system in direct comparison, but participants who used blocks to solve tasks performed better on average than hybrid system users and gave higher usability ratings. These findings suggest that despite the appeal of data-flow programming, a well-adapted block-based programming interface can lead end-users to more programming success.

Programming industrial robots is difficult and expensive. Although recent work has made substantial progress in making it accessible to a wider range of users, it is often limited to simple programs and its usability remains untested in practice. In this article, we introduce Duplo, a block-based programming environment that allows end-users to program two-armed robots and solve tasks that require coordination. Duplo positions the program for each arm side-by-side, using the spatial relationship between blocks from each program to represent parallelism in a way that end-users can easily understand. This design was proposed by previous work, but not implemented or evaluated in a realistic programming setting. We performed a randomized experiment with 52 participants that evaluated Duplo on a complex programming task that contained several sub-tasks. We compared Duplo with RobotStudio Online YuMi, a commercial solution, and found that Duplo allowed participants to solve the same task faster and with greater success. By analyzing the information collected during our user study, we further identified factors that explain this performance difference, as well as remaining barriers, such as debugging issues and difficulties in interacting with the robot. This work represents another step towards allowing a wider audience of non-professionals to program, which might enable the broader deployment of robotics.

Abstract Newly released robot programming tools have made it feasible for end‐users to program industrial robots by combining block‐based languages and lead‐through programming. To use these systems effectively, end‐users, who usually have limited or no programming experience, require training. To train users, tutoring systems are often used for block‐based programming—some even for lead‐through programming—but no tutorial system combines these two types of programming. We present CoBlox Interactive Tutorials (CITs), a novel tutoring approach that teaches how to use both the hardware and software components that comprise a typical end‐user robot programming environment. As users switch between the two programming styles, CITs provide them with extensive scaffolding, give users immediate feedback on missteps, and provide guidance on next steps. To evaluate CITs, we conducted a study with 79 industrial end‐users using a programming environment released by ABB Robotics that compares our approach to training with training videos, the most commonly used training in industry. This study, one of the largest to date on training professional end‐users, found that CIT‐trained users authored more correct programs in less time than video‐trained users. This shows that a tight integration of hardware and software concepts is crucial to training end‐users to program industrial robots.

Block-based programming environments, already popular in computer science education, have been successfully used to make programming accessible to end-users in domains like robotics, mobile apps, and even DevOps. Most studies of these applications have examined small programs that fit within a single screen, yet real-world programs often grow large, and editing these large block-based programs quickly becomes unwieldy. Traditional programming language features, like functions, allow programmers to decompose their programs. Unfortunately, both previous work, and our own findings, suggest that end-users rarely use these features, resulting in large monolithic code blocks that are hard to understand. In this work, we introduce a block-based system that provides users with a hierarchical, domain-specific program structure and requires them to decompose their programs accordingly. Through a user study with 92 users, we compared this approach, which we call guided program decomposition, to a traditional system that supports functions, but does not require decomposition. We found that while almost all users could successfully complete smaller tasks, those who decomposed their programs were significantly more successful as the tasks grew larger. As expected, most users without guided decomposition did not decompose their programs, resulting in poor performance on larger problems. In comparison, users of guided decomposition performed significantly better on the same tasks. Though this study investigated only a limited selection of tasks in one specific domain, it suggests that guided decomposition can benefit end-user programmers. While no single decomposition strategy fits all domains, we believe that similar domain-specific sub-hierarchies could be found for other application areas, increasing the scale of code end-users can create and understand.

Modern industrial robots can work alongside human workers and coordinate with other robots. This means they can perform complex tasks, but doing so requires complex programming. Therefore, robots are typically programmed by experts, but there are not enough to meet the growing demand for robots. To reduce the need for experts, researchers have tried to make robot programming accessible to factory workers without programming experience. However, none of that previous work supports coordinating multiple robot arms that work on the same task. In this paper we present four block-based programming language designs that enable end-users to program two-armed robots. We analyze the benefits and trade-offs of each design on expressiveness and user cognition, and evaluate the designs based on a survey of 273 professional participants of whom 110 had no previous programming experience. We further present an interactive experiment based on a prototype implementation of the design we deem best. This experiment confirmed that novices can successfully use our prototype to complete realistic robotics tasks. This work contributes to making coordinated programming of robots accessible to end-users. It further explores how visual programming elements can make traditionally challenging programming tasks more beginner-friendly.

The application of program transformations and refactorings involves the risk of capturing variables, which may break the intended semantics of the transformed code. One way to resolve variable capture is by renaming of the involved identifiers. However, in a modular context, the renaming of exported declarations is undesirable (affecting a module's clients), and the renaming of imported declarations is impossible (requiring changes to third-party modules). We present an algorithm name-fix that detects and eliminates variable capture modularly. We extend a previous non-modular version of name-fix in order to (i) minimize renamings of exported declarations, (ii) propagate necessary renamings of exported declarations to clients, and (iii) avoid renamings of imported declarations altogether. Together with support for transitive name bindings and conflicting declarations, our extensions to name-fix enable the application to real-world languages that feature separate compilation. To demonstrate the applicability of name-fix, we use it to modularly resolve variable capture for optimizations, refactorings, and desugarings of Lightweight Java.