## 2 Literature Overview
### Maintenance Maturity Models  
The literature analysis conducted demonstrates that the recognition of the current maturity state of the maintenance process in the organisation is a mandatory step to determine the specific need in an industrial context and, consequently, a successful adoption of an MMIS; for this reason, an exploratory study on these systems was carried out. The purpose of the Maintenance Maturity Models (MMM) analysis is to understand what the main aspects are for developing a maturity model for the maintenance information management domain. Maturity models have proliferated across a multitude of domains since the concept of measuring maturity was introduced with the Capability Maturity Model (CMM) from the Software Engineering Institute (SEI)--Carnegie Mellon [23]. Maturity models can be seen as a simple method that allow organisations to effectively measure the quality of their processes. During the last two decades, the application fields for maturity models have widened. In the study of [PERSON] [10], who proposed the first systematic summary of the maturity model research, two points of view are underlined when developing a maturity model:  
1. The life cycle perspective identifies those models having a well-defined 'final' stage of maturity that will be reached while evolving. Therefore, it may serve as a tool for management supporting the development of the examined objects. The idea is that an organisation evolves over time and, therefore, automatically must pass all the stages due to the improvements and learning effects. The user may decide if it is desirable to proceed to the next stage. 2. The potential performance perspective is principally used for the same purpose as above, but with a slight difference. These models show a development path, too, but the stages focus on the potential improvements that occur by moving along. Maturity models, regardless of the perspective, describe and determine the state of perfection or completeness (maturity) of certain capabilities. The application of this concept is not limited to any domain. Therefore, maturity models define simplified maturity stages or levels that measure the completeness of the analysed objects via different sets of (multi-dimensional) criteria. This explanation is reflected in the definition by [PERSON] [24]: 'A maturity model consists of a sequence of maturity levels for a class of objects. It represents an anticipated, desired, or typical evolution path of these objects shaped as discrete stages. Typically, these objects are organisations or processes.' To summarise, two relevant issues must be considered during maturity models' development: the definition of maturity levels along which the examined object evolves and the criteria for measurement. The identification and characterisation of maturity levels have been discussed in various knowledge areas, such as in project management, quality management and systems development, and the practical application of findings has led to the achievement of better results [11]. The first maturity model was introduced in the quality management area by [PERSON] and [PERSON] [25]. Maturity models allow an organisation to have its methods and processes evaluated by good management practices and with a set of external parameters. Typically, a maturity model consists of the following components [26]:  
1. the number of maturity levels (ML),
2. a descriptor for each level, (e.g., uncertainty, certainty),
3. a description of the characteristics expected of an organisation at each level,
4. the number of dimensions,
5. a description of the elements/activities at each dimension,
6. a description of each activity as performed at each maturity level. Over the past few decades, maturity models have been developed and applied in different areas encompassing product development, software management, patient safety culture, information management and risk management [24; 27; 28].