System Architecture Design

pSHIELDSystem Architecture DesignPUThe figure also highlights the correspondence between the class diagram and a classical feedback controlscheme (including Process, Controller and Sensing/Actuation functionalities) where:• the Process to be controlled is represented by the three horizontal layers (Node, Network andMiddleware)• the Controller is the Security Agent supported by the Semantic Knowledge Repository• Sensors/Actuators are represented by the Core SPD Services lying at the pSHIELD MiddlewarelayerThe formalized conceptual model of the pSHIELD Overlay is shown in the following figure. Taking intoaccount that the pSHIELD Overlay can include several Security Agents each one controlling a pSHIELDsubsystem, the pSHIELD Overlay model is easily obtained by composing in parallel the feedback controlscheme relevant to each Security Agent presented in the previous figure. The coordination andinformation exchange between the different controllers (i.e. SPD Security Agents) is performed by meansof metadata (referred to as exchanged metadata). The advantages in terms of flexibility entailed by thismodular approach are evident.Figure 35 – Formalized conceptual model for the pSHIELD Overlay.6.5 System Overall ArchitectureIn order to formally describe the pSHIELD system overall architecture, we decided to use the UMLcomponent diagram formalism, where there could be identified the following formal elements:FUNCTIONALCOMPONENTPHYSICALCOMPONENTIMPORTINTERFACEEXPORTINTERFACEFigure 36 – pSHIELD functional architecture formalism.PUD2.3.2Issue 5 Page 107 of 122