## 2 State of the Art  
### PC or Web Simulators for Glucose Concentration Levels  
In recent years, an effort to implement glucose levels simulators has been made. One standard option for implementing simulators are PCs or Leptops. PCs have as their main advantage the inherent high computational power for performing simulations. In addition, there has been a trend to replace PCs with much more compact devices, such as smartphones, but most simulators for glucose concentration are PC-based. Another implementation option consists of Web systems, allowing for a broad range of devices to access such simulation systems. Web-based simulators have an advantage: many platforms can access the simulator compared to a particular PC implementation. Web-based simulators have as main disadvantage the requirement of Internet connectivity, making the simulator difficult to access in places with connectivity problems.  
In [10], the AIDA diabetes simulator is presented, and extensive evaluation about this simulator has been reported in [11]. Recently, new types of rapid-acting insulins have been added to the AIDA diabetes simulator [12]. AIDA's mathematical model was created to simulate glucose tolerance; however, its use is not based on daily periods.  
In [13], the REACTION project is presented. This project consists of a set of healthcare services oriented to diabetic patients and caregivers through a cloud-based application focusing on management and therapy services. The REACTION project is a management system created for the implementation of logistics related to medical personnel. The dosage management algorithm is based on basic rules, and it is not a pharmacological-dynamic behavioral study of insulin. In other words, it is a mathematical model with experimental parameters.  
In [14], GLUCOSIM is proposed as a desktop application designed to do virtual experiments to show the effects of food intake changes and insulin therapy on glucose levels. A more detailed version of this system is reported in [15], where a Web-based solution was included. It is important to mention that GLUCOSIM is a tool designed to study, train and analyze the external effects that modify glucose concentration. It uses three mathematical models to consider all the mentioned effects; however, it does not describe periods of exercise or other modeled effects.  
In [16], a system is proposed based on the combination of Compartmental Models (CMs) and artificial Neural Networks (NNs). Data from a Type 1 diabetes patient, which contains information about measured blood glucose levels, insulin intake, and food intake description, along with the corresponding time, were used as input to the model. The proposed strategy was not adequately validated. Furthermore, no performance criteria were mentioned to assess the results objectively.  
The literature review indicates that early studies of compartmental modelling of glucose/insulin interactions were proposed since the 1980s in [17; 18; 19]. On the other hand, recently, different research groups have reported important works related with the implementations of compartmental models to develop glucose level simulators, for example, in [20; 21] are presented a glucose forecasting algorithm based on a compartmental composite model of glucose-insulin dynamics. In [22] is developed a dynamic model for type 1 diabetic patient that focuses on blood glucose regulation. A first model for insulin adsorption in infusion sets using a minimal lumped two-compartment modelling approach is reported in [23]. A review of the key role of the UVA/Padova simulator is presented in [24], which has tested the use of new molecules for better glucose control.