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PCo - Path for the Source

Former Member
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Hi,

I want to extract the entire path ("Source") of a subscription item in PCo. I can only see the tag name in the xml notification. Appreciate your thoughts.

Regards,

Chanti.

Accepted Solutions (1)

Accepted Solutions (1)

Former Member
0 Kudos

Chanti,

There are no functions that pull the Source field in an Agent Instance's Notification output expression. I don't fully understand your situation, but I will assume that you have multiple items with the same name but different source paths (ex. Device1.Tag1 and Device2.Tag1) while pointing to the same MII transaction as a destination. In this case, I would do the following;

- Rename your Selected Item Name to something more meaningful to ensure you are pulling the right tag. You can do this when browsing for items and adding them. Just double click in the Name field. Then your renamed Subscription Item will appear when configuring an expression for Output. Also, you should also have a good naming convention for Agent Instances and Notifications as a best practice.

Your MII transaction can then do processing as necessary...

Hope it helps,

Kevin

Former Member
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We already concluded upon having a good naming convention for the agent instances and went with it.

Personally, I still think if there is a way PCo could extract the source path, would be the best. Hence, left the thread open.

Regards,

Chanti.

Former Member
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Chanti,

Good to hear about using naming conventions. As for the Source path, what do you plan to do with it?

Kevin

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Chanti,

Have you considered using alias mode to logically group your tags?

Sam

Former Member
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We are maintaining our tag data (names, program data etc.) in R/3. The source path (combination of server, workcenter, tag name) acts as a unique identifier when communicating to the tags. The main thing is when we receive feedback from PLCs we need to update the records in R/3 using a unique identifier. We tried using a GUID, but the problem is to hold it temporarily somewhere. We would like to keep MII stateless.

Former Member
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Are you refering to alias in UDS? We are trying to replace a legacy MES system. The tags have already been existing.

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Yes, I'm referring to Alias mode in the UDS which would allow you to name them whatever you would like without modifying anything in the historian system.

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What is the purpose of the GUID in your design? If it's stateless in MII then the GUID approach doesn't seem to fit your model. If it's to track if a message has been received then why not use the data buffering in MII or a custom DB table if buffering is unavailable?

Former Member
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I don't believe custom DB table is an option. Its not always tracking if a message has been received. Sometimes, PCo monitors for changes in tag values and communicates with R/3. I will look into the data buffering option.

I will also have to look into the alias thing in UDS. I am new to it. Do you have a sample transaction?

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The alias is configured specific for the UDS/PCo agent so you can have an "aliased" and "standard" connection to your historian. For the agent mode you will see "Alias..." as an option and then you can browse and define tag name mappings in the UDS/PCo tool, it's documented in the Help in much more detail; I guess the secret here is knowing that it exists in the first place.

Answers (0)