Over the years, a substantial body of knowledge of software process improvement (SPI) was accumulated that, among other things, includes numerous success factors that companies should consider when conducting improvement activities. The number of success factors is large and quite often, multiple success factors with similar names and descriptions are available to address a specific phenomenon. This raises the question whether all the success factors are unique and, if not, which ones are actually the same. In this paper, we aim to structure the body of knowledge on success factors in SPI. We conducted a systematic literature review on 103 publications that mention 1.320 success factors. A multi-staged manual and AI-supported analysis reduced the number of success factors to 124, which we categorize into 42 general success factor classes. For 20 of these general success factor classes, we observed a stable number of publications over a period of almost 30 years that, however, show only few success factors constantly studied and re-discovered. A high number of synonyms shows that this area of SPI needs consolidation for which we lay the foundation by providing a big picture and identifying the most relevant success factors as a starting point.

With the emergence of agile software development methods, new approaches for determining agile maturity have become necessary. Other than for traditional maturity and capability models like CMMI and ISO/IEC 15504, the field of agile maturity models is not yet settled. Even worse, a common understanding regarding agility in general and the levels of agility in particular is missing. The paper at hand aims to shed light on the field of agile maturity models with a particular focus on maturity levels, their definition, and their evaluation and computation. We conducted a systematic literature review to extract maturity levels and provide an initial harmonization of the levels found. Our findings from analyzing 19 agile maturity models show that there is yet no agreement with regard to the maturity levels. In total, 69 maturity levels have been analyzed for harmonization opportunities. Two major dimensions of maturity levels of agile maturity models could be identified: (1) team-related and (2) general maturity, which is comparable to standard approaches. However, the procedures to assess organizations and processes, if at all present, are to a large extent focused on persons and their personal opinion, which paves the way for future research, e.g., in terms of developing measurement systems for assessing agile maturity.