The notion of "plug-out" does not seem to convey the key OPES concept that an OPES entity operates on a data flow between a data provider and a data consumer.
On the other hand, the concept (not sure about the English) perhaps applies well in explaining Web Services?
Totally right (my Frenglish made me to thing in/out as location rather than the way they are used). I used your image in a Web Service presentation. It worked just fine. I followed you advice to and compared OPES to "converters", and detailed talking about filter and transformer for the dispatcher and callout server. Was immediately understood. Is that better and acceptable English/image?