RE: [DM] stable order

> section 3.2 Document Order of the XQuery 1.0 and XPath 2.0 
> Data Model uses the term "stable" to characterize orders. I 
> do not find any definition in this document what a stable order is.

I agree that this is missing. I think that in other documents we use a
phrase such as "consistent for the duration of a query or transformation",
which reflects the intent.

> 
> Do you mean, if two nodes A and B whose order is 
> implementation-dependent are in some concrete order then this 
> order doesn't change within this model (for the lifetime of 
> this instance; never)? Does it have to be the same order 
> between two invocations of an implementation?

Who can say what the lifetime of an instance is?
> 
> Moreover, regarding distinct documents, the specification says
> 
>    "The relative order of nodes in distinct documents is 
>    implementation-dependent but stable. In other words, given two 
>    distinct documents A and B, if a node in document A is before a 
>    node in document B, then every node in document A is before every 
>    node in document B."
> 
> That sounds as if the second sentence ("In other words, ...") 
> is a conclusion or an explanation of the term "stable order", 
> but I can't 
> apply this meaning to attribute or namespace nodes.

I think the "In other words" is wrong. The second sentence is saying
something quite different from the first; it is saying that although it's
implementation-defined whether nodes from document D precede or follow nodes
from document E, they are never going to be intermingled.

Michael Kay

Received on Tuesday, 24 June 2003 12:46:27 UTC