## 4 CAS Development  
The development methodology used to develop the smart irrigation CAS is the mini-waterfall methodology [15]. Additionally, CASO and IRRIG ontologies have been developed following the linked open terms (LOT) methodology [16]. A mini-waterfall is a methodology used for system engineering. It is inspired by the well-known waterfall methodology, which develops a system in five activities: (1) specification, (2) design, (3) implementation, (4) testing and (5) maintenance. The purpose of the mini-waterfall methodology is to repeat the sequence of the five activities multiple times to develop the system progressively. LOT is a methodology used for ontology engineering. It was first proposed in [16] and further developed at [17]. LOT is inspired by agile techniques in which sprints aim to align ontology development with software development agile practices. This methodology focuses on (1) the reuse of terms (classes, properties and attributes) existing in already published vocabularies or ontologies and (2) the publication of the ontology following the linked data principles. LOT relies on the ontological engineering activities defined in the NeOn methodology [18] when available. LOT defines iterations over the following four activities: (1) ontological requirements specification, (2) ontology implementation, (3) ontology publication, and (4) ontology maintenance. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Watering cycle duration** & 9 to 10 days & 6 to 8 days & below 5 days \\ \hline
**Median of 30 cm depth probes** & 30 cbar & 50 cbar & 60 cbar \\ \hline
**Median of 60 cm depth probes** & 10 cbar & 20 cbar & 20 cbar \\ \hline
**Sum of the median of 30 cm depth probes** & 40 cbar & 70 cbar & 80 cbar \\ and the median of 60 cm depth probes** & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Decision table of the relation of the watering cycle duration and the soil moisture for maize at growth stage V2. Figure 3 illustrates the smart irrigation CAS development methodology combined with the ontology development methodology. Ontology development has a life cycle called the LOT life cycle. The LOT life cycle is presented by the dashed yellow box. Each activity in this life cycle is represented by a solid yellow box. The solid black arrows between the boxes show the order of the activities; for example, the development team must perform the ontological requirements specification activity before the ontological implementation activity. The CAS development life cycle is called a mini-waterfall life cycle. It is presented by the dashed blue box. Each activity in this life cycle is represented by a solid blue box. The solid yellow arrow between one activity \(X\) in the LOT life cycle and one activity \(Y\) in a mini-waterfall life cycle means that the result of activity \(X\) is necessary to implement activity \(Y\). For example, the design activity of the mini-waterfall cycle requires the result of the ontology conceptualization activity of the LOT life cycle. Otherwise, the dashed blue arrow from one activity \(Y\) of mini-waterfall to one activity \(X\) of LOT life cycle means that the result of the activity \(Y\) can contribute to activity \(X\). It is necessary to note two items in this methodology. First, the LOT life cycle is triggered by the mini-waterfall life cycle, but it is independent of the mini-waterfall life cycle. Consequently, the LOT life cycle can be shorter than the mini-waterfall life cycle. Suppose that after each development life cycle, there is a new version. Therefore, there is nothing to prevent the ontology from having three versions at the same time, but the system can only have one version. Second, after the maintenance activities of both the LOT life cycle and CAS life cycle, the development team renews the sequence, i.e., starts with the first activity. However, they can skip the current activity if they find that the last time result of the same activity is sufficient.