## 2 Materials and Methods
### User Acceptance and Usage  
End users were included in the entire process from the very beginning, preparing data and testing the interface. After the first month of the development phase, they started to use the system actively, often requesting additional functions, meaning that development continued in concert with usage. Users of the system were divided into three groups: data administrators, data analysts, and public users. T public health system in Bosnia and Herzegovina is regulated in accordance with the administrative authorities of two entities, a district and ten cantons. The users from thirteen public health institutions together with users from clinical centers and microbiological laboratories were continuously collecting, entering, and validating data. This group has varied from 20 to 30 participants using ELIS as a mostly evidence-based system for the country level. A group of data analysts consisting of 22 experts from these public health institutions, university clinical centers, and five faculties of medicine have used ELIS as an expert system and produced reports about spread analysis and evaluation of the epidemic situation for different areas and time periods [14; 23]. Geographical, demographic, and other data combined with epidemic data was processed using the selected analytical methodology, and the results were arranged in the ELIS geoportal in the form of diagrams, attribute tables, interactive maps, and animations. The third group, public users including press workers, has used ELIS as an informative portal to understand the current situation as well as the history of spread. The number of public visitors on a daily basis has consistently exceeded one hundred. The realization of the described methodology is based on the following architectural concept for the system development (Figure 3a):  
The front end is a JavaScript web application that communicates with web services using AJAX and allows for the connection to different mapping libraries. The front end is based on the ReactJS library and the Redux architecture, which is a specific implementation of the Flux architecture. The back end consists of a set of web services developed in Java, and includes services for HTTP-Proxy, storage of unstructured resources, and security, with the ability to configure authentication using internal or external services, and flexible authorization policies for access to services and resources. ELIS is based on the following tech stack:  
* MapStore is an Open Source highly modular web GIS framework developed by GeoSolutions to create, manage and share securely in a simple and intuitive way maps created by mixing geospatial contents served from servers like Google Maps, OpenStreetMap, Bing, or from servers adhering to OGC standards like WFS, CSW, WMS, and WMTS;
* GeoServer is an open-source server that generates maps and controls spatial data. It implements OGC standards like WMS, WFS, and WCS. Its interface has tools to add, update, and delete data sources and layers, as well as set styles;
* OpenLayers is used for the development of front end applications such as the JavaScript library, which enables browsing and interacting with spatial data via web browsers; and
* PostgreSQL with PostGIS, which is used as DBMS [21]. Based on the architecture described above and the concept of Web 2.0, the system provides a free classification of information, a responsive interface with dynamic content, user participation in terms of changing data and interface, and software as a service based on APIs. It includes standard analytical tools such as interactive maps, control panels, various diagrams, etc. The user interface, as its client segment, lets different types of users work easily, especially the non-IT-expert users. Each logged-in user is assigned the appropriate services (maps, dashboards, database schemas) [22].