I agree with Rich that the function identifiers should be changed to reflect the expanded definitions in 3.0.
I don’t agree that the change is superfluous. The non-bag arguments are processed as constant arguments to the Boolean function named in the first argument
of any-of or any-of-any. The only built-in XACML 3.0 Boolean function that takes more than two parameters is time-in-range. But I imagine that Jan’s use cases for GeoXACML would have other Boolean functions of 3 or more arguments, which is probably why he
wanted to generalize the functions. However, new identifiers should be provided since the new definition is not backward-compatible with existing implementations.
I think any-of-any should require at least two bag arguments (like the other *-of-* functions), with optional scalar arguments.
Regards,
--Paul
From: [mailto:]
On Behalf Of rich levinson
Sent: Thursday, 12 January, 2012 01:04
To: Erik Rissanen
Cc:
Subject: Re: [xacml] New issue: XACML 3.0 higher order bag functions may have significant problems
Hi Erik,
I expected that there was background material that provided the motivation,
however, looking at the result, it seems to me that the "any-of" fcn has
been expanded in an unnecessary way, since it appears to me that the
change of the 2nd parameter in 2.0 to be n-1 parameters in 3.0, really
is providing individual elements in separate parameters that could just
as well be provided in a bag as they already are in the "any-of-any" fcn.
Also, the "any-of" is ref'd in some of the other fcns, presumably as
being an "atomic" one element 2nd parameter fcn. That ref'ing I expect
becomes less meaningful as the 2nd parameter expands to effectively
be a bag implemented as multiple parameters.
It looks to me as if what might have seemed like a good idea at the
time may have emerged as being duplication of existing functionality
by effectively providing a less usable alternative to a bag as an
n-1 list of individual parameters.
I think in the email you ref'd when you said:
"With this definition the any-of function actually becomes
a special case of any-of-any, with one primitive type argument
and one bag argument."
that you and I are possibly in technical agreement, although we may have
different perspectives on it.
Unless there has been some real functionality added w this n-1 construct,
my recommendation would be to fall back to the 2.0 impl and remove
the n-1 parameter construct in 3.0.
Thanks,
Rich
On 1/11/2012 11:49 PM, Erik Rissanen wrote:
Hi Rich,
Please see this post:
http://lists.oasis-open.org/archives/xacml/200912/msg00087.html
(And other discussion on this issue.)
Best regards,
Erik
On 2012-01-12 00:19, rich levinson wrote:
I was perusing thru section A.3.12 today, looking at some of the details
of the higher order bag functions, and it appears to me that there have
been some changes made in 3.0 that do not look right.
For example, let's compare the 2.0 and 3.0 definitions of "any-of". Some of the
diffs are subtle, so I have bolded, italicized the points I want to call attention to.
Note: I have tried to line up the paragraphs line by line of the 2 defns. Do not
pay too much attention to the line numbers as they are sometimes off by 1
from the original because of quirks in copy and paste.
Here are the points about the 2.0 vs 3.0 definitions:
Both 2.0 and 3.0 have the same name: xacml:1.0:function:any-of,
therefore, one would expect the functions to be identical. I think
we will find that the are not only not identical, but have some
very strange differences.
There is a difference in the hi-level defn of the fcns, where 2.0 uses
the singular (compares 1 value to bag of values), and 3.0 uses the plural
(compares multiple values to one bag of values).
It appears that the change to plural is intentional, as will be evidenced
in the points below, however, at this stage, it would appear that at
the very minimum that the "name" of the 3.0 fcn should be different
than the name of the 2.0 fcn.
The most important change is that the 2nd argument of 2.0, has become
"n-1" arguments in 3.0. i.e. the "signature" of "any-of" has changed from
3 arguments to "n+1" arguments, because of the expansion of the 2nd
argument. Aside from this change in quantity of arguments, I believe
the semantics have also changed, and maybe not in a good way.
In 2.0, the function was effectively:
"Does the 2nd argument appear in the bag in the 3rd argument?"
In 3.0, this function appears to have become:
"Does the 2nd argument appear in the bag in the last argument?
Does the 3rd argument appear in the bag in the last argument?
...
Does the nth argument appear in the bag in the last argument?
If any of the above answers are "yes" then return true, ow false."
We do not know on a true return which of the 2nd thru nth args
matched something in the bag. Maybe all of them matched
something, maybe only one, or maybe some number in between.
Based on prev bullet 4, this new variation on the "any-of" fcn
begins to look suspiciously like the "any-of-any" fcn that compares
2 bags looking for anything in bag 1 that matches anything in bag 2.
Therefore, it appears to me that the 3.0 defn of "any-of" actually
"implements" "any-of-any", which seems pointless.
I think there may be other similar issues in this section, but this one
is the only I have had time to look at in detail.
As usual, I am aware I may be missing something, in which case,
in advance, "Never mind" :).
The text of 2.0 and 3.0 follows:
Thanks,
Rich
First, here is 2.0:
4558 • urn:oasis:names:tc:xacml:1.0:function:any-of
4559 This function applies a Boolean function between a specific primitive value and a bag of
4560 values, and SHALL return "True" if and only if the predicate is "True" for at least one
4561 element of the bag.
4562 This function SHALL take three arguments.
The first argument SHALL be an <xacml:Function> element that names a Boolean function
that takes two arguments of primitive types.
The second argument SHALL be a value of a primitive data-type.
The third argument SHALL be a bag of a primitive data-type.
The _expression_ SHALL be evaluated as if the function named in the <xacml:Function> argument
were applied to the second argument and each element of the third argument (the bag)
and the results are combined with “urn:oasis:names:tc:xacml:1.0:function:or”.
Now, here is 3.0:
4680· urn:oasis:names:tc:xacml:1.0:function:any-of
4681 This function applies a Boolean function between specific primitive values and a bag of
4682 values, and SHALL return "True" if and only if the predicate is "True" for at least one
4683 element of the bag.
This function SHALL take n+1 arguments, where n is one or greater.
The first argument SHALL be an <Function> element that names a Boolean function
that takes n arguments of primitive types.
Under the remaining n arguments, n-1 parameters SHALL be values of primitive data-types and
one SHALL be a bag of a primitive data-type.
The _expression_ SHALL be evaluated as if the function named in the <Function> argument
were applied to the n-1 non-bag arguments and each element of the bag argument
and the results are combined with “urn:oasis:names:tc:xacml:1.0:function:or”.
