# CONDA-PM--A Systematic Review and Framework for Concept Drift Analysis in Process Mining
## 4 Research Methodology
### Sources  
The search string was applied to _five electronic libraries_ in order to discover studies related to the topic \"concept drift\". These electronic libraries are as follows:  
* Elsevier_ ([[https://www.sciencedirect.com/](https://www.sciencedirect.com/)]([https://www.sciencedirect.com/](https://www.sciencedirect.com/)))
* _IEEE Xplore Digital Library_ ([[https://ieeexplore.ieee.org/Xplore/home.jsp](https://ieeexplore.ieee.org/Xplore/home.jsp)]([https://ieeexplore.ieee.org/Xplore/home.jsp](https://ieeexplore.ieee.org/Xplore/home.jsp)))
* _SpringerLink_ ([[https://link.springer.com/](https://link.springer.com/)]([https://link.springer.com/](https://link.springer.com/)))
* _ACM Digital Library_ ([[https://dl.acm.org/](https://dl.acm.org/)]([https://dl.acm.org/](https://dl.acm.org/)))
* _Google Scholar_ ([[https://scholar.google.com/](https://scholar.google.com/)]([https://scholar.google.com/](https://scholar.google.com/)))  
These libraries contain repositories of journal articles as well as the most relevant conference and workshop proceedings in the field. Furthermore, the libraries provide capabilities of filtering results based on different criteria, like year of publication, subject, and type (e.g., conference proceedings, journal article, technical report). Moreover, Google Scholar alerts were set to trigger us when recent studies on the topic, which match parts of the search string, had emerged. Based on this variety of libraries, we aimed to retrieve high quality published studies with a minimum overlap between them. Finally, we applied _backward reference searching_ by further examining sources referenced by more than one of the included studies. The results were saved in an Excel sheet ([[https://drive.google.com/file/d/1](https://drive.google.com/file/d/1) KLdt5 yg4 EiN_Fw-AMEgWMulJjDuIDLA/view?usp=sharing]([https://drive.google.com/file/d/1](https://drive.google.com/file/d/1) KLdt5 yg4 EiN_Fw-AMEgWMulJjDuIDLA/view?usp=sharing)), to which inclusion and exclusion criteria were applied. Each study was initially analysed to extract the following information:  
* _Abstract._ This criterion was the necessary for gaining an overview of the topic and contributions of a study.
* _Title._ This criterion was the determinant in the first round of selecting relevant studies to be included in the SLR.
* _Year of publication._ The more recent a study is, the more it builds upon knowledge gained from previous works. Furthermore, more recent publications constitute potential sources for identifying other studies by conducting backward reference searching. Finally, less recent studies have been expected to be analysed in more recent ones, that is, this kind of analysis was surveyed as well.
* _Type._ This criterion was one of the determinants of the maturity level of a study, for example, publications in conference proceedings are expected to provide more mature approaches than the ones published in workshop proceedings. Moreover, journal publications are considered being most mature and detailed.
* _Publisher._ The publishing institution has a weight on the expected quality of research done through a study. For example, publishers like Elsevier, IEEE Xplorer, and Springer are known for editing high impact factor journals and conference proceedings.
* _Number of citations._ This criterion was one of the indicators of the relevance on the considered approach. Sometimes, the number of citations was influenced by the year of publication. Furthermore, we came to the conclusion that the number of citations is influenced by the direction an approach is pursuing. This intuition was developed after deriving the directions of studies, which are introduced in Section 5. However, we did not consider the number of citations as a main criterion for including or excluding a study as it will be affected by the year of publications, especially for the studies published between 2017 and 2019.