[New-ITS] Node counts

[Robert Worden]

David - 

 

Just to clarify what I have counted, because we seem to have got wires
crossed on factors of 10.

 

The things I am counting are distinct nodes in a message definition, not
allowing repeats of nodes or self-nesting. Put another way, I am
counting distinct XPaths in the message definition, short of
self-nesting. Inasmuch as each XPath is a name for a set of nodes, that
is sort-of counting the names of nodes in the message.

 

I made these counts in two ways:

 

1.       going right down to leaf nodes of the XML

2.       stopping at V3 data type nodes, counting each V3 data type top
node as 1.

 

Doing this for a couple of messages, I got:

 

- PA 'new person' - 1100 XPaths down to data type nodes, 77000 nodes
down to leaves

- Lab 'observation request' 65,000 XPaths down to data type nodes, 4.4
million down to leaves.

 

So the 65,000 is not 10% of anything - sorry to have misled you. BTW the
lab number only includes 1 of the 4 choices at the top.

 

For both messages, the average multiplier from data type nodes to leaves
is 70. This is dominated by a few large data types which have large
counts on leaf nodes:

 

type: PQ; count: 175

type: IVL_TS; count: 548

type: AD; count: 135

type: PN; count: 592

type: CV; count: 129

type: CR; count: 213

type: ON; count: 576

type: CE; count: 383

type: CD; count: 129

type: PQR; count: 171

type: EN; count: 592

 

When you weight these by occurrences, there are a few main culprits: Out
of the 4.4 million leaf nodes in the lab message:

 

type: ON; count: 315072

type: II; count: 108030

type: CE; count: 1657241

type: IVL_TS; count: 980920

type: AD; count: 238545

type: EN; count: 873792

 

Now I guess the big data types are almost never nearly 500 nodes in
instances, and simplified versions can be learned by developers for use
in 99% of cases; so the huge numbers of leaves (average 70 per data
type) does not worry me too much.  But 65,000 separate XPaths in one
message, before you get down to data types, does worry me. 

 

By the way, I was really quoting these numbers to agree with you - if
node count is at all sensible as a measure of complexity, then any
automatic or centrally decreed message flattening will do no good at
all, because it hardly reduces node count. I don't think flattening per
se will reduce the developer learning curve. I agree with you that HL7
should not increase the burden of message formats it imposes on itself
or its implementers. It should let them do their own message reshaping
when they want to - knowing they can always 'reflate' messages to be V3
conformant, automatically and accurately,  if their recipients prefer a
RIM-centric approach. 

 

Best wishes

 

Robert

 

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