Re: [uima] "Assignment Style" vs. "Functional Style"

[Thilo W Goetz <TGOETZ@de.ibm.com>]

To my mind, the data in the CAS is just
that: data.  That data is much more like the data in a database than
objects in a programming language.  So I wouldn't even call this approach
"functional style", it's more like "data in, data out",
or passing a reference to a database.  If I have a sentence annotation,
for example, over a stretch of text, I have no notion of that annotation
as an object; rather, there is a piece of information that tells me that
there is a sentence from x to y in my input text.

I would not like to change this model
for the following reasons:

Functionality: there may very
well be service implementations that can not guarantee a procedural behavior,
for whatever reason.  I think we shouldn't disallow such services
a priori in the spec.

Performance: I would not like
to see applications that don't need this behavior having to pay the price
for it.  We would need to create a mapping from CAS internal object
IDs to XMI IDs on serialization, keep it around.  Then create a similar
mapping on the service side on deserialization and keep it around.  When
the service serializes the CAS again it needs to respect the mapping, and
the application that receives the results from the service will in turn
need to respect its mapping when deserializing.

Not enforceable: all a service
needs to do to be compliant is to not reuse any input IDs (unless I missed
something).  I'm assuming that we're only talking about FSs that are
indexed, since we're freely dropping non-indexed FSs on serialization,
anyway.

Implementation: the weakest argument
of all, but I would like to keep the ability to, for example, compact the
CAS heap between calls to processors.  If I need to keep references
into the heap intact (without knowing who's holding them), I can't do anything
like that.  No garbage collection, no paring down of the CAS because
only a small subset of the data is needed for further processing etc.  We
haven't really implemented any of that anyway, but if we wanted to implement
features like that, requiring referential integrity from the outside, so
to speak, would make this very hard or impossible.

Mit freundlichen Gruessen / Best regards

Thilo Goetz
OmniFind & UIMA development
Information Management Division
IBM Germany
+49-7031-16-1758

IBM Deutschland Entwicklung GmbH
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Geschäftsführung: Herbert Kircher
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Adam Lally <alally@us.ibm.com>

04/30/07 15:57

To	carl.madson@sri.com, j.tsujii@manchester.ac.uk, Sophia.ananiadou@manchester.ac.uk, "uima@lists.oasis-open.org" <uima@lists.oasis-open.org>
cc
Subject	[uima] "Assignment Style" vs. "Functional Style"

Hi everyone, 

I tried to capture the issues we discussed on the last telecon regarding
whether UIMA's component/service interfaces should use an assignment style
(take a CAS and update it) or a functional style (take a CAS and return
a new CAS).  See the attached document. 

Thilo and/or Thomas probably have more that they would like to add to this
discussion.  Anyone else is of course free to jump in as well.



Regards, 
  -Adam 
_____________________________
Adam Lally
Advisory Software Engineer 
UIMA Framework Lead Developer
IBM T.J. Watson Research Center
Hawthorne, NY, 10532
Tel: 914-784-7706,  T/L: 863-7706
alally@us.ibm.com[attachment "AssignmentVsFunctionalStyle.doc"
deleted by Thilo W Goetz/Germany/IBM]