An Investigation into Inner Source Software Development: Preliminary Findings from a Systematic Literature Review Henry Edison Noel Carroll Kieran Conboy Lero, National University of Lero, National University of Lero, National University of Ireland Galway Ireland Galway Ireland Galway [email protected] [email protected] [email protected] Lorraine Morgan Lero, National University of Ireland Galway [email protected] ABSTRACT INTRODUCTION Given the value and effectiveness of open source software Open Source Software (OSS) has been highly prevalent in development to date, practitioners are keen to replicate these both practice and research. Given the value and effectiveness practices inside their respective corporations. This application of open source development to date, practitioners are keen to of open source practices inside the confines of a corporate replicate these practices inside their respective corporations. entity has been coined inner source software development. This application of open source practices inside the confines However, while organisations have found ways to directly ben- of a corporate entity has been coined inner source software efit from revenue streams as a result of leveraging open source (ISS) development [7, 49, 16, 41]. ISS development has been practices internally, the current research on inner source is seen as a way in which organisations adopt OSS [17, 19]. scattered among different areas. Thus gaining clarity on the Leading organisations such as Lucent Technologies, Nokia, state-of-the-art in inner source research is challenging. In Philips, IBM and HP etc, have provided example of inner particular, there is no systematic literature review of known source implementations [5], which has led to the emergence research to date on inner source. We address this challenge of studies on inner source in the scientific literature (e.g. [23, by presenting a systematic literature review that identifies, 24, 42, 41, 43]). critically evaluates and integrates the findings of 29 primary While the literature purports that ISS development presents studies on inner source. Case study approach is the common many benefits for internal use, there have been growing re- research approach undertaken in the area. We also identified 8 search efforts to equally highlight the challenges associated frameworks/methods, models and tools proposed in the liter- with adopting and scaling inner source practices. However, ature to support inner source, as well as a set of benefits and challenges associated with inner source. We envision future understanding the state-of-the-art in inner source research is work to perform deeper analysis and synthesis on the empirical challenging. Capraro and Riehle [5] recently published a re- research on inner source software development. view on inner source literature. Although the findings are significant and shed light on the grey area of ISS development, the inner source research field remains dispersed among dif- ACM Classification Keywords ferent research areas. Thus, the objective of this study is to D.2.9 Software Engineering: Management – Software process understand the current research that has been carried out on the models; K.6.3 Management of Computing and Information usage of ISS development or the application of OSS principles Systems: Software Management – Software development, within existing organisations. This objective is broken down Software maintenance, Software process into the following research questions: (i) RQ1 - What research methods have been used in studies on ISS development? (ii) Author Keywords RQ2 - What types of contributions are provided by the studies inner source software development, inner source, systematic on ISS development? and (iii) RQ3 - What are the reported literature review, open source benefits and challenges associated with ISS development? Permission to make digital or hard copies of all or part of this work for personal or The remainder of this article is structured as follows. Section classroom use is granted without fee provided that copies are not made or distributed 2 presents a brief discussion of related work in this area and for profit or commercial advantage and that copies bear this notice and the full citation followed by a presentation of our research approach in Section on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, 3. In Section4, we present an overview of the characteristics to post on servers or to redistribute to lists, requires prior specific permission and/or a of the primary studies. The key findings of this study are fee. Request permissions from [email protected]. presented in Section5, and discussed in Section6. Finally, the OpenSym ’18, August 22–24, 2018, Paris, France conclusion is presented in Section7. © 2018 ACM. ISBN 978-1-4503-5936-8/18/08. $15.00 DOI: https://doi.org/10.1145/3233391.3233529 RELATED WORK key papers in a specific area of interest, and evaluating and We identified four secondary studies [17, 19,6,5] on inner interpreting the reporting discussions and findings [21]. A source that were considered relevant to this study. For exam- defined review protocol, search strategy, explicit inclusion and ple, Hauge et al. [17] and Höst and Oruceviˇ c-Alagi´ c´ [19] per- exclusion criteria, and specified information that will be re- formed literature reviews by following the guidelines provided trieved from primary studies differentiates a systematic review by Kitchenham and Charters [21]. The study by Crowston et from a conventional literature review [21]. al. [6] could be considered partly systematic, since the rele- vance can be seen in terms of search strategy, data sources, Search Strategy inclusion/exclusion criteria and data extraction. On the other To help build the search terms, a set of key papers were iden- hand, the study by Capraro and Riehle [5] presented an exten- tified by all authors. Keywords used in these papers were sive literature review but showed no evidence of following any extracted and aggregated and used as the input for the search systematic guidelines. terms. From the key papers, we extracted a total of 76 key- words (30 unique). The top three keywords are “open source” Both Hauge et al. [17] and Crowston et al. [6] conducted (23.68%) and “software development” (19.74%), and “inner a search on specific journals or conferences on open source, source” (10.53%). while Höst and Oruceviˇ c-Alagi´ c´ [19] and Capraro and Riehle [5] only focus on software engineering related databases such The search terms were organised into three groups: interven- as Inspec, Compendex, ACM Digital Library and IEEE Xplore. tion, control and population, and separated by AND-clauses. Furthermore, Hauge et al. [17] did not report the used search Table1 describes the generic search strings. The developed string and Capraro and Riehle [5] did not reveal the timespan search terms were then searched through in two digital libraries for the search. (EngineeringVillage and Scopus) to view its effectiveness. Re- visions to the search terms were made until we were able to Neither Crowston et al. [6] nor Capraro and Riehle [5] used retrieve all the key papers from these two digital libraries. explicit criteria for quality assessment of the primary studies, which hinders interpretation. Contrary to these studies, Hauge A search for relevant literature was conducted on the title, et al. [17] and Höst and Oruceviˇ c-Alagi´ c´ [19] adopt the quality abstract and keyword. We decided to use digital libraries assessment criteria developed by Dybå and Dingsøyr [8]. For that have good coverage, familiarity, reputation, advanced our review, we adopted a comprehensive set of evaluation features and exportability [10]. The digital libraries used to guidelines based on scientific rigour and industrial relevance search for relevant literature were relevant to (i) SE research: proposed by Ivarsson and Gorschek [20]. Compendex, ISI Web of Science and Scopus [9,3], and (ii) IS research: AIS e-Library. The actual search was performed The aim of the review conducted by Hauge et al. [17] and Höst in August 2017. We collected and analysed articles that have and Oruceviˇ c-Alagi´ c[´ 19] was to assess the current research on been published until August 2017. how organisations adopt OSS, while Crowston et al. [6] inves- tigated the state of research on open source in general. These Group Terms studies found that there is a lack of studies on open source Intervention {inner?source} OR innersource software practices inside organisations. Capraro and Riehle (key concepts) OR {open?source} OR opensource [5] developed a model of the elements that constitute inner Control (con- software source. The study also presents a classification framework text) for inner source programs and projects, and a map of known Population organi?ation OR firm OR company inner source endeavours, as well as qualitative models sum- (scope) OR corporat* OR enterprise marising the benefits and challenges of inner source adoption. OR industr* OR vendor OR All studies identify that there is a trend towards organisational institution* OR internal OR adoption of open source principles in their internal develop- inside OR hybrid ment processes. Table 1. Search terms organisation In summary, among the existing relevant literature reviews, the study by Capraro and Riehle [5] is only one study that is closer in similarity to our study. One notable difference between Selection Strategy the study by Capraro and Riehle [5] and our study is the Studies were eligible for inclusion in this study if they are systematic approach we adopted for our research methodology (i) peer-reviewed papers, (ii) written in English, (iii) full-text and the coverage of the search. The study by Capraro and available, and (iv) focusing on ISS development or the adop- Riehle is more of a literature survey than a systematic literature tion of OSS principles within an organisation. Both theoretical review (SLR).