## 6 Discussion  
### Summary of Research Questions and Their Answers  
1.1 RQ1: How Do Different Maintainability Index Variants Perform When Utilized for the Maintainability Measurement of a Single Object-Oriented Software System? The results of different variants of an Index used to assess the maintainability of object-oriented software systems can vary greatly. To ensure the most-accurate assessment, the specific variant selected should take into account the relevant aspects of maintainability that best represent the maintainability of the software system in question. For example, if code documentation significantly benefits software maintainability, a variant incorporating code comments into the Index computation should be used. Note that some human analysis of the comments is recommended to aid this decision [10; 36]. The differences between the values produced by different Index variants are, in most cases, significant  
Figure 9: Lollipop plots depicting the change in Index variants’ values from the previous release. and should not be overlooked. Typically, the Index variants without the comment part have closer values, as well as the Index variants with the comment part. Additionally, the former tend to have lower values compared to the latter. As a result, this makes it difficult to compare values obtained from different variants directly. Furthermore, using originally proposed thresholds for conventional systems to convert the maintainability assessment on an interval scale, which ranges from an unbounded negative number to 171, into categorical, i.e., low, medium, and high maintainability, may not be appropriate without considering the object-oriented nature of the software system and the specific Index variant used to make the maintainability assessment. 1.2 RQ2.1: How Do Different Maintainability Index Variants Perform When Utilized for Maintainability Measurement between Different Software Systems? Although there are differences in the values produced by different variants of an Index used to measure software system maintainability, the variants tend to behave similarly when comparing maintainability between systems. The relationship between all pairs of Index variants under study is positive and strong to very strong. When comparing two software systems based on their maintainability assessments from different Index variants, if one software is easier to maintain than the other according to one variant, it is very likely that the same holds true according to any other variant. Moreover, when comparing the maintainability of software systems using different variants of the Index, very similar outputs can be expected for all variants without the comment part and all variants with the comment part. On the other hand, when comparing the maintainability of systems using two Index variants, one from each of the two groups, the consistency in the maintainability comparison is expected to be lower. These findings reinforce the importance of carefully considering which variant of the Index to use for the maintainability assessment, namely taking into account whether or not code documentation should be considered. 1.3 RQ2.2: How Do Different Maintainability Index Variants Perform When Utilized for Maintainability Measurement between Versions of the Same Software System? When comparing the maintainability of different versions of the same software using different Index variants, the relationship between the variants remains positive, but can range from moderate to very strong. It can be observed that, in the case when comparing the maintainability between releases of the same software system, i.e., when changes in the source code are small, the Index variants tend to be more prone to non-consistency in the maintainability comparisons. This means that when focusing on finer-grained results posed by the Index, the selection of the Index variant has even more of an impact on the maintainability perception.