A major challenge to teaching and assessing a first year undergraduate programming module is that students arrive with different prior programming experience. We address this problem by adopting a competencies-based assessment approach for narrowing the learning gap for less experienced students while still challenging those with more experience. Students can work at different paces and their progress is monitored real-time, allowing for early intervention. We share lessons learned and provide tips to help educators implement this in their modules.

Failed error propagation (FEP) is known to hamper software testing, yet it remains poorly understood. We introduce an information theoretic formulation of FEP that is based on measures of conditional entropy. This formulation considers the situation in which we are interested in the potential for an incorrect program state at statement s to fail to propagate to incorrect output. We define five metrics that differ in two ways: whether we only consider parts of the program that can be reached after executing s and whether we restrict attention to a single program path of interest .We give the results of experiments in which it was found that on average one in 10 tests suffered from FEP, earlier studies having shown that this figure can vary significantly between programs. The experiments also showed that our metrics are well-correlated with FEP. Our empirical study involved 30 programs, for which we executed a total of 7,140,000 test cases. The results reveal that the metrics differ in their performance but the Spearman rank correlation with failed error propagation is close to 0.95 for two of the metrics. These strong correlations in an experimental setting, in which all information about both FEP and conditional entropy is known, open up the possibility in the longer term of devising inexpensive information theory based metrics that allow us to minimise the effect of FEP.

Slicing is useful for many software engineering applications and has been widely studied for three decades, but there has been comparatively little work on slicing extended finite state machines (EFSMs). This paper introduces a set of dependence-based EFSM slicing algorithms and an accompanying tool. We demonstrate that our algorithms are suitable for dependence-based slicing. We use our tool to conduct experiments on 10 EFSMs, including benchmarks and industrial EFSMs. Ours is the first empirical study of dependence-based program slicing for EFSMs. Compared to the only previously published dependence-based algorithm, our average slice is smaller 40 percent of the time and larger only 10 percent of the time, with an average slice size of 35 percent for termination insensitive slicing.

This paper introduces Model Projection. Finite state models such as Extended Finite State Machines are being used in an ever increasing number of software engineering activities. Model projection facilitates model development by specializing models for a specific operating environment. A projection is useful in many design-level applications including specification reuse and property verification.

Dependence analysis underpins many activities in software maintenance such as comprehension and impact analysis. As a result, dependence has been studied widely for programming languages, notably through work on program slicing. However, there is comparatively little work on dependence analysis at the model level and hitherto, no empirical studies. We introduce a slicing tool for Extended Finite State Machines (EFSMs) and use the tool to gather empirical results on several forms of dependence found in ten EFSMs, including well-known benchmarks in addition to real-world EFSM models. We investigate the statistical properties of dependence using statistical tests for correlation and formalize and prove four of the empirical findings arising from our empirical study. The paper thus provides the maintainer with both empirical data and foundational theoretical results concerning dependence in EFSM models.

B has been widely used for high-integrity systems development, for example in the railway industry. However, there are few published guidelines on how to structure B specifications for particular types of system, such as reactive control systems. In this paper, we describe a method to support the graphical design of systems using the B abstract machine notation (AMN), and we develop guidelines for expressing the structuring requirements of reactive systems in B.