# A Survey on Modeling Languages for Applications Hosted on Cloud-Edge Computing Environments
## 3 Results
### Relationships, Dependencies and Environment Values
In GENTL [9], relationships between components are represented using a Connector that captures the association between a source component and a target component. GENTL allows for the definition of attributes associated with the Connector, such as deployed on, which help specify the type of the Connector as there may be multiple classes of Connector. In CAMEL [1], when users describe application component instances, they define a communication instance in the requirement section. The communication instance enables users to describe the communication between components or binding between components and hosts. The host relationship instance binds a component instance with a virtual machine instance, and the connect relationship instance describes the communication between components. In HOT, templates are used to specify the relationships between resources, such as describing the connections between a volume and a server. There are models like FRACTAL4 EDGE [35] that are designed for edge-cloud computing environments and focus on infrastructure-related aspects. FRACTAL4 EDGE supports a single type of relationship that facilitates the connection of physical devices to each other for sharing results within the edge-cloud computing environment. Similarly, the UML extension proposed in [28] employs the specification level deployment diagram, in which developers can describe how physical nodes interact with each other in order to provide a desired result. The deployment model of SMADA-Fog [12] introduces types of relationships between physical devices not previously discussed in this paper. The masterServer relationship signifies that a host has the role of a master and is responsible for managing other servers. Additionally, within the specific network device type of SMADA-Fog, there is a relationship called managesNF that describes the SDN controller's ability to enforce traffic shaping rules within the software-defined network for the devices under its control, including both physical devices and virtual network functions. The deployment model of SMADA-Fog incorporates the connectedTo relationship to depict the communication between network devices and other device types. The same model of SMADA-Fog enables the utilization of the hasLocation relationship, linking a host to its execution environment (Edge-Cloud), and the hasEnvironment relationship, which links a Task to its designated execution environment (Edge-Cloud) for running. [PERSON] et al. in [21; 22] present a novel approach in their Self-adaptive IOT DSL for communication representation. The language relies on the MQTT (Message Queuing Telemetry Transport) messaging protocol for communication among IoT devices and other nodes. This allows IoT devices acting as publishers or subscribers using the Topic relationship to engage with specific topics on an MQTT broker. Additionally, the DSL allows for the modeling of gateways for IoTDevices through the gateway relationship, establishing connections with EdgeNode concepts. This facilitates communication between sensors and various nodes, including the MQTT broker node. The research also introduces the concepts of clusters, employing the master relationship to indicate the master node and the worker relationship to represent workers. The communication between nodes is depicted with the linkedNodes relationship. Furthermore, the proposed DSL enables a container composition relationship, describing the deployment of a container to a host node. The utilization of graphical user interface (GUI) tools can significantly simplify the process of expressing relationships between components and resources. FRACTAL4 EDGE [35], MoDMaCAO [23], the UML extension [28] and Uni4 Cloud [13] serve as notable examples of modeling tools that employ GUIs for this purpose. These tools enable developers to visually represent and depict the relationships between components through the utilization of graphical elements such as arrows.