WriteMask and UserWriteMask not compiling correctly

[herrmannultraschall-jsl]

Hi UA-ModelCompiler Team,
I have a problem compiling the WriteMask and UserWriteMask from OPC model design xml to nodeSet2.xml. According to UA Attributes.xml, it is allowed to set these two attributes to control the write access of the DisplayName and Description of a node.

From UA Attributes.xml:

<opc:Constant Name="WriteMask">
   <opc:Documentation>Indicates which attributes are writable.</opc:Documentation>
</opc:Constant>
<opc:Constant Name="UserWriteMask">
   <opc:Documentation>Indicates which attributes are writable by the current user.</opc:Documentation>
</opc:Constant>

When I try to give write access to the attributes DisplayName and Description in my OPC model design xml file like so:

<opc:Object WriteAccess="96" SymbolicName="quantum:Weldprogram3" TypeDefinition="quantum:WeldprogramType">

or like so

<opc:Object SymbolicName="quantum:Weldprogram3" TypeDefinition="quantum:WeldprogramType">
   <opc:BrowseName>Weldprogram3</opc:BrowseName>
   <opc:DisplayName>Custom Weldprogram 03</opc:DisplayName>
   <opc:Description>Weldprogram number 3.</opc:Description>
   <opc:WriteMask>96</opc:WriteMask>
   <opc:UserWriteMask>96</opc:UserWriteMask>

I end up getting no equivalent tag in the compiled nodeSet2.xml file (as if the model compiler could not compile it and just "swallows it").

What I am expecting is, that by setting the WriteMask and/or the UserWriteMask, one or both are compiled correctly into this:

  <UAObject NodeId="ns=8;i=46819" BrowseName="8:UltrasonicStack3">
    <DisplayName>Custom Ultrasonic Stack 03</DisplayName>
    <Description>Ultrasonic Stack number 3.</Description>
    <WriteMask>96</WriteMask>
    <UserWriteMask>96</UserWriteMask>

If I set <WriteMask>96</WriteMask> and <UserWriteMask>96</UserWriteMask> directly into the compiled nodeSet2.xml it all works fine. Our OPC server reads it correctly and the attributes are writable (checked with the tool UA Expert: UA Expert)

Conclusion
So for me, there is a compilation error in the ModelCompiler or a wrong input on my side.

Please correct me if I am wrong with my input and close the issue, otherwise please fix the bug.

Additional Information
In our production code we now have a workaround implemented that patches nodes inside nodeSet2.xml with the WriteMask and UserWriteMask where we want the DisplayName and Description to be writable. We are pretty unhappy with that solution. I hope you can help the situation.

Looking forward to hearing from you. Thank you very much in advance.
Regards,
Johannes Stoll (Herrmann Ultrasonics Germany)

[opcfoundation-org]

UserWriteMask, UserAccessLevel and UserRolePermissions cannot be set in a design file since they are dependent on a User associated with a Session.

It is not clear why adding an arbitrary XML child element in the design file will result in it being copied to the NodeSet. This is a bug. The WriteMask in the UANodeSet schema is an XML attribute so a WriteMask element has no defined meaning.

The WriteAccess XML attribute in the ModelDesign is not currently mapped to WriteMask XML attribute because of an unresolved issue over what it means. Specifically, does it specify the WriteMask for all instances of Type or does it only apply to the Type nodes.

When loading a UANodeSet in to a Server address space, the Server is expected to update the Nodes based on its needs. i.e. the references are only 1-way in the NodeSet but a Server needs to turn most of them into 2-way references. Applying access rights to the Nodes based on design requirements is another.

[herrmannultraschall-jsl]

Hi opcfoundation-org,
thanks for your reply!

I guess the takeaway from what you said is that the UserWriteMask, UserAccessLevel and UserRolePermissions cannot be set in the ModelDesign since they are user dependent. I understood that part but what about the WriteMask? As I understood, you said that the WriteAccess XML attribute in the ModelDesign is currently not mapped to a WriteMask XML attribute or tag inside the nodeSet2.xml because of an unresolved issue regarding its meaning.

I asked Copilot about what the meaning of a WriteMask in OPC is and how it works:

Meaning
Copilot -Meaning of WriteMask
Controlling the write access to attributes of OPC nodes for a client.

Function
Copilot - Function of WriteMask
Settings the correct bitmask of 96 (dec) shall result in write access to the node attributes "displayname" and "description" (as long as no additional user permission prevents that.

Bit Mask
According to OPC - AttributeWriteMask the write access to the node attributes "displayname" and the "description" are as follows (bit 5 and bit 6, zero-based counting).

OPC Bit Mask
---------------------------------------------------------
0	0	0	0	0	0	0	0    . . .
---------------------------------------------------------
1	2	4	8	16	32	64	128
					^	^	
0.	1.	2.	3.	4.	5.	6.	7.

32 + 64 = 96

I set in DesignXml file the write access like so (directly on instance, not via type):
<opc:Object WriteAccess="96" SymbolicName="quantum:TestWeldprogramTopSealPouch"

Result: as I mentioned in the opening post -> no luck, not working

OPC Default
Default
Not having set the WriteMask shall result in being able to write any attribute (as long as no additional user permission prevents that).

Can you please elaborate on what the remaining unresolved issues with the WriteMask are?

Thank you and best regards,
Johannes Stoll

[opcfoundation-org]

The issue is not the spec says but what the ModelCompiler currently implements.
The ModelCompiler does not provide any way to set the WriteMask.
The WriteAccess XML attribute is not used at all.

Most servers don't care because they set the WriteMask/UserWriteMask when the NodeSet is loaded because the WriteMask that should be used can depend on the Server when information models are used by different Servers (i.e. one Server may support writing the DisplayName but another may not; Being able to Write a DisplayName is a semantic associated with an implementation and not an information model).

It would be possible to add support for the WriteMask to the ModelCompiler .

[herrmannultraschall-jsl]

Hi opcfoundation-org,
thanks again for your reply.

I guess, we at Herrmann Ultrasonics (and perhaps many other developers in the industry too) would appreciate it if the ModelCompiler would be able to make use of the WriteAccess XML attribute to set a WriteMask by design. Especially when manufacturers of industry equipment (like we are with our ultrasonic generators) know that they will only ever load exactly one information model into a specific device's OPC server of the same type (always a 1:1 relationship between information model and OPC server; no sharing of information models across device types/opc servers), they would want the ModelCompiler to support the WriteMask.

Also, the AccessWrite XML attribute is already provided by the schema for the ModelDesign.xml file. Why not supporting it consequently then.

In short, we would highly appreciate the decision to support the WriteMask in a future release of the ModelCompiler or in a preview version and would want to use it since our OPC server Open62541 supports it already.

Thank you for your support and the clarity you gave on the topic.

How do I request this feature? Is it necessary to request it explicitly to be taken into consideration in the roadmap of the ModelCompiler?

Best regards,
Johannes Stoll

[opcfoundation-org]

Will add support.