Re: [foxboro] OPC again...
- From: <tom.vandewater@xxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Wed, 2 May 2007 14:54:32 -0400
I've heard people talk about the tunneler. To my understanding
it uses TCP/IP to pipe from one machine to another instead of DCOM in a
similar manner as Modbus TCP. I would feel a lot better about that than
using DCOM. The old OPC DA,(Data Access),OPC HDA,(Historical Data
Access),and OPC A&E (Alarms and Events), used COM/DCOM for its transport
mechanism and it has been a good idea gone bad because of DCOM.
There were several reasons that motivated the OPC Foundation to
develop the new OPC UA, (Unified Architecture) and the limitations and
problems associated with COM/DCOM were significant drivers for change.
OPC UA based on Web Services/Service Oriented Architecture may alleviate
a lot of these issues. The best article I've read to gain a better
understanding of UA and its features and intent was written by
Stefan-Helmut Leitner and Wolfgang Mahnke of the ABB Corporate Research
Center in Germany. The link to the document, listed below will be
broken and you will have to copy and paste it into your browser to make
it work:
http://pi.informatik.uni-siegen.de/stt/26_4/01_Fachgruppenberichte/ORA20
06/07_leitner-final.pdf
Abstract: OPC Unified Architecture (OPC UA) is the new standard of the
OPC Foundation providing interoperability in process automation and
beyond. By defining abstract services, OPC UA provides a
service-oriented architecture (SOA) for industrial applications - from
factory floor devices to enterprise applications. OPC UA integrates the
different flavors of the former OPC specifications into a unified
address space accessible with a single set of services. This paper gives
an overview of the architecture of OPC UA, its address space model and
its services. It discusses the necessary security mechanisms needed to
allow secure access over the internet. Finally, migration strategies to
OPC UA applications are introduced.=20
Cheers,
Tom VandeWater
Control Systems Developer/Analyst
Dow Corning Corporation
Carrollton, KY USA
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