Hi,
I also came back from vacation this week and just had a quick look at P.
I still don't believe that the problem we are trying to solve calls for
a (albeit limited) programming language like P. In fact, I think a rule
module written in P would be more difficult to understand and write by
people who don't already have experience with programming languages.
What I like about an XML-based language like IRML is that by design it
limits the complexity of rule modules. IRML rule modules can be
represented as well es edited graphically (using a generic XML editor)
in a tree where nodes represent rule conditions and leaves resulting
actions. I think such a representation would be more intuitive and
easier to understand than a piece of P code. Also, when editing IRML
rules generic XML editors can provide rule authors with immediate
feedback if rule modules violate the IRML DTD or XML syntax. I don't
think this can be easily done with P.
I also don't agree with all of the design goals that Alex lists in the
introction to P. For example, I don't see a need for the rule language
to be so compact and efficient that it can be interpreted on the fly. I
cannot imagine that an ISP would let an OPES system process arbitrary
rules in real time as it receives them from data providers/consumers. I
think there will have to be an offline validation and optimization step.
That way the OPES system can rewrite or throw out inefficient or
malicious rule modules that would slow down the OPES system excessively
or unnecessarily otherwise.
That having said, I believe that there is still a lot of potential to
further improve IRML if the WG decides to pursue an XML-based rule
language. For example, CPL (which solves a very similar problem in the
IP tel. space and is also XML-based) has a mechanism that allows CPL
script authors to easily re-use parts of a CPL script through a
reference to it. I would be willing to work on a new IRML draft version
to incorporate such a mechanism as well as address some of Alex'
comments on IRML. I guess what is needed at this time is for more people
on the list to speak up and voice their opinion on the two rule language
proposals.
-Andre
Martin Stecher wrote:
Hi,
back from holiday I just read draft-rousskov-opes-rules-00 quickly.
In a first reaction, it makes a lot of sense to me and I find it easier to
understand and more powerful than IRML.
Though I have a little problem with the example in Figure 10:
"toDialect" is a term that is very specific for the selected service.
Does this example assume that "toDialect" is a supported term of standard P
or how could a service dynamically add new identifiers and functions calls?
While I can follow Alex comments about IRML and like P better than IRML in the
moment, I admit that I did not deal a lot with the rule language requirements
all the time, so I may oversea important aspects.
I would very much appreciate if an IRML advocate (Andre?!?) could comment on
Alex draft and list problems and aspects that IRML solves better. Such as Alex
did before with IRML.
Regards
Martin
-----Original Message-----
From: Alex Rousskov [mailto:rousskov(_at_)measurement-factory(_dot_)com]
Sent: Tuesday, September 02, 2003 6:58 PM
To: OPES WG
Subject: Re: moving along on rules language
On Tue, 2 Sep 2003, Markus Hofmann wrote:
Alex - I'd suggest you publish this as individual ID right away
rather than just having a URL as reference. Would give us all a
formal reference for the document.
Submitted with minor polishing touches.
Alex.
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