Sorry, I have no idea, so please allow me to ask this question ;-)

What does the following mean, -> pos="-1" in the XML row here?

And does the negative value -1 itself have a special meaning? Remember, there are no questions that cannot be asked ;-)

Regards

CodePudding user response：

With the info, especially the context, which you provide in your question, or better do not provide in your question, the answer is:
We are looking at XML code which opens and immediatly closes an element named "attr". Syntactically it has several named attributes. One of them is named "pos" and has the value "-1".
What semantical meaning that "-1" has is unknown and can only be interpreted with additional but unavailable (at least here) information.
All in all, this is an example of XML acting as eXtendable Markup Language which can be used for any kind of information. The fact that XML is used for this specific information does not mean that it gives it a meaning.
This is basically the point of XML.

CodePudding user response：

A fragment of XML means whatever the sender and recipient agree that it means. Very often some third party will have defined a schema that defines what elements and attributes are allowed in a message, and that says how they should be interpreted. In some informal data flows, the schema is never formally defined but is just a matter of mutual understanding among the user community.

My guess would be that pos="-1" means "the position is unknown or not applicable", but I might be wrong; it could mean "the point of sale was the customer service counter".

I just noticed that you've tagged the question DICOM. It would have been a good idea to mention DICOM more explicitly in your question, because DICOM probably provides the answer. I've never heard of DICOM until today, but I see that it's a standard for medical imaging information, and there's thousands of pages of specification. One one of those pages it will tell you what pos="-1" means.