Context: Smells in software systems impair software quality and make them hard to maintain and evolve. The software engineering community has explored various dimensions concerning smells and produced extensive research related to smells. The plethora of information poses challenges to the community to comprehend the state-of-the-art tools and techniques. Objective: We aim to present the current knowledge related to software smells and identify challenges as well as opportunities in the current practices. Method: We explore the definitions of smells, their causes as well as effects, and their detection mechanisms presented in the current literature. We studied 445 primary studies in detail, synthesized the information, and documented our observations. Results: The study reveals five possible defining characteristics of smellsindicator, poor solution, violates best-practices, impacts quality, and recurrence. We curate ten common factors that cause smells to occur including lack of skill or awareness and priority to features over quality. We classify existing smell detection methods into five groups-metrics, rules/heuristics, history, machine learning, and optimization-based detection. Challenges in the smells detection include the tools' proneness to false-positives and poor coverage of smells detectable by existing tools.

The realisation of domain-speci®c languages (DSL DSLs) diers in fundamental ways from that of traditional programming languages. We describe eight recurring patterns that we have identi®ed as being used for DSL DSL design and implementation. Existing languages can be extended, restricted, partially used, or become hosts for DSL D SLs. Simple D SL DSLs can be implemented by lexical processing. In addition, DSL DSLs can be used to create front-ends to existing systems or to express complicated data structures. Finally, DSL DSLs can be combined using process pipelines. The patterns described form a pattern language that can be used as a building block for a systematic view of the software development process involving DSL DSLs. Ó

Apart from source code, software infrastructures supporting agile and distributed software projects contain traces of developer activity that does not directly affect the product itself but is important for the development process. We propose a model that, by combining traditional contribution metrics with data mined from software repositories, can deliver accurate developer contribution measurements. The model creates clusters of similar projects to extract weights that are then applied to the actions a developer performed on project assets to extract a combined measurement of the developer's contribution. We are currently implementing the model in the context of a software quality monitoring system while we are also validating its components by means of questionnaires.

Freebsd is a sophisticated operating system developed and maintained as open-source software by a team of more than 350 individuals located throughout the world. This study uses developer location data, the configuration management repository, and records from the issue database to examine the extent of global development and its effect on productivity, quality, and developer cooperation. The key findings are that global development allows round-the-clock work, but there are some marked differences between the type of work performed at different regions. The effects of multiple dispersed developers on the quality of code and productivity are negligible. Mentoring appears to be sometimes associated with developers living closer together, but ad-hoc cooperation seems to work fine across continents.

The integrity verification of a device's controlling software is an important aspect of many emerging information appliances. We propose the use of reflection, whereby the software is able to examine its own operation, in conjunction with cryptographic hashes as a basis for developing a suitable software verification protocol. For more demanding applications metareflective techniques can be used to thwart attacks based on device emulation strategies. We demonstrate how our approach can be used to increase the security of mobile phones, devices for the delivery of digital content, and smartcards.