## 2 Use Case (UC) Description, IOP Methodology and Concept Applied
### Use Case Description  
In this case, we examine the interaction between the data concentrator and the smart meters, and the data messages sent by the smart meters to the data concentrator. Therefore, the configuration of interest is the connection between the smart meters and the data concentrator. The objective is to study the system performance in case fundamental parameters are altered and the effect of such parameters  
Figure 1: Interoperability Testing Methodology [1]. UC: Use Case, BAP: Basic Application Profile, BAIOP: Basic Application Interoperability Profile, TC: Test Case, EUT: Equipment Under Test. on the system interoperability. For this reason, the role of Design of Experiments in the interoperability methodology is important along with the statistical analysis of the results. In [19] the concept of a scoring scheme for interoperability testing in the context of AMI is introduced. This scoring scheme is accompanied by a test verdict tracing scheme that can be used for pointing the tangible interoperability layer of the Smart Grid Architecture Model (SGAM) framework [13] that is responsible for lack of interoperability when such a case occurs. In this work, the \"quality of interoperability\" between the relevant components of interest is investigated. To clarify what is meant by the phrase \"quality of interoperability\", the reader has to take into account the following: the dynamics of interactions between two (or more) components of interest are characterised by a hierarchy of interactions. This hierarchy is defined in relevant communication protocol specification documents, e.g., [20]. Normally, two types of entities exist, a \"requesting\" and a \"responding\" one. The \"requesting\" entity is on the higher-level of the hierarchy, and the \"responding\" entity is on the lower-level of the hierarchy. In Figure 2, a generic form of interactions between relevant components is presented. With respect to the framework within which the components of interest perform the functionalities that they are assigned to perform, different metrics can be used for assessing their performance. For example, the metric used can be the \"sampling period of requests\" asked by the \"requesting entity\". This metric can take different values, and the quantity that is assessed is the \"response rate\" of the \"responding entity\". At this point, there is a need to clarify some issues relevant to the \"pass\" or \"fail\" test verdict. As introduced in [19] a \"fail\" test verdict can take place on any of the tangible interoperability layers of the SGAM, i.e., component, communication and information layers. To link this work with the definition for lack of interoperability introduced by the authors of [19], the following has to be considered: An indisputable \"fail\" test verdict means that the \"response rate\" of the \"responding entity\" is 0%. For any value greater than 0% an investigation for the sufficiency of interoperability has to take place. This is done because if the response rate is greater than 0%, it means that the system under test is capable of interoperating on the tangible interoperability layers and, thus, the system as a whole can be considered as interoperable. The \"quality of interoperability\" is then linked with the observed, through experimentation, \"response rate\". The higher the value of the \"response rate\", the more significant the value offered by the interoperable system turns to be. In this case, the actors involved are the smart meter(s) and data concentrator. The mapping of this use case on the SGAM component, communication and information layers can be represented as shown in Figures 3 and 4. Figure 2: Dynamics of interaction between two components of interest. It is considered that the Local Network Access Point (LNAP) is within the smart meter, whereas the Neighbourhood Network Access Point (NNAP) is actually the data concentrator. The interfaces C and M define the standards that can be used for each link of communication.