Managing configuration of relatively big config files via "node types" in SCA OPC-UA server

Piotr P. Nikiel, August 2019


Rationale

The configuration file of the SCA OPC-UA server describes different aspects such as:

A sample configuration per SCA taken from the NSW DCS is:

What is expected (and confirmed by users) is that often content as above is likely to be repetitive - e.g. same contents between SCA tags will be used, only with different name and address attributes.

The problem

The problem is that redundant content is difficult to manage.

Copy-pasting should be avoided.

The solution

It is proposed that XML entity references are used.

Each repetitive part (e.g. in the example above, everything contained within SCA tags - excluding SCA themselves) can be put in a separate XML file - let's say here it is put into SCA_type1.xml.

Then the external entity is defined as below (before configuration tag)

The contents of sca-entity.xml can then be inserted in a chosen place(s) of the config file by:
&SCA_TYPE_1;


Of course, there can be multiple entities defined and each entity can be reused any number of times.