This specification defines an OPC UA AddressSpace to manage IO-Link Masters and their connected IO-Link Devices. To manage the IO-Link Devices without detailed knowledge of the device an IODD is needed to interpret the structures provided by the device. However, managing IODDs might be hard for servers running on small embedded devices with very limited resources. Therefore, this specification defines a server facet only providing the basic functionality without IODD interpretation (see section 15.4.1). This allows the implementation of such a facet with very limited resources, but requires that the client has knowledge about the device, either implemented in the client or implicitly by the user of the client.

The following section describes a solution to combine the benefit of an IODD interpretation and thus allowing full device access without detailed knowledge of the device by the user and the implementation of an OPC UA Server on very limited resources, by adding an aggregating server into the system providing the IODD based access.

The basic implementation of an OPC UA Server without IODD (see section 15.4.1) is done on very limited resources, like for example the IO-Link Master itself. A system likely will have several of those simple servers. In addition, an aggregating server implementing the IODD management and interpretation capabilities (see section 15.4.2) as well accesses the simple servers and adds the IODD management and interpretation capabilities on top. As the simple server interface already allows ISDU access, the ISDU logic can be triggered by the aggregating server. This aggregating server typically would have enough resources to manage a large amount of IODDs, potentially even having access to get more IODDs by using tools like the IODD finder. Users would access the aggregating server to get the IODD based information of all connected IO-Link Masters. Figure 27 gives an example for such an architecture.

Figure 27 – System Architecture using an OPC UA aggregation server for IODD capabilities (Example)

Several variations of that approach are possible. The aggregating server might, in addition to the OPC UA based sources also proprietarily access IO-Link Masters. There might be several aggregating servers in a system, etc.