I agree that there is (and can be) no such thing as a "generic
miracle parser", but I don't think that it what is being called for.
There is no "generic miracle parser" for context free languages,
either, but there are still tools such as yacc/bison that vastly
simplify the process of constructing parsers from a given grammar.
Certainly, there are trade-offs, too. The Earley parser has a
theoretical performance of O(n^3), but is able to parse arbitrary
CFGs. Shift-reduce parsers are limited to LR(k) (usually LR(1))
grammars, but are much more efficient (especially when sentences may
be very long). In the area of XML, SAX and DOM are very generic tools
(but considerably much more powerful than what VistA HL7 provides
today), but tools such as XML data binding and various SOAP
implementation provide much richer functionality.
I suppose that I'm saying is that there is a trade-off here. At one
extreme, thee are so-called Turing complete languages that are very
expressive, but that expressiveness comes at a cost in terms of
complexity. More narrowly constrained processing rules can be
implemented as well, often allowing a much higher degree of
automation than is supported by the VistA HL7 package. The reason
that we have regular expressions and finite automata at one extreme,
recursive descent parsers, shift-reduce parsers, Earley or CYK
parsers, and finally full featured programming languages, is that
each offers a trade-off between expressiveness/flexibility on the one
hand, and ease of use on the other.
===
Gregory Woodhouse
[EMAIL PROTECTED]
"The most profound technologies are those that disappear."
--Mark Weiser
On Sep 12, 2005, at 4:29 PM, Clemens, John wrote:
Vista's HL7 package supports both inbound and outbound messaging just
fine. There is no such thing as a 'generic miracle parser' for inbound
data. If you know your message structure coming in and you know your
local application and database it is trivial to parse the message and
store the data where you want it. All HL7 interfaces work pretty much
that way whether you are Vista or a commercial vendor. You can
leverage
many of the existing interfaces developed within the VA for storing
lab,
pharmacy, ADT, etc or you can use them as a basis for a customized
interface. If messages strictly adhere to the standard, you would
pretty
much know what to expect in every message, but ONLY you would know
where
you want to store your data. It is simpler than XML to implement,
though
version three help keep things simple.
I apologize if I've misunderstood some of the previous comments but
I am
a strong supporter of HL7 and the Vista implementation. Some of the
newer features however can only be found in the patch documentation
and
I don't know what the rules are for sharing that information (if any).
Best,
John Clemens
San Francisco VA Medical Center
Tu-Wed-Thu: 415.221.4810 x4540
Mon,Fri: 650.464.7585 (personal cell)
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