Re: [Jsdsi-users] extending jsdsi.Tag

[Sameer A. <aj...@cs...>]

Comments below...

> On Wed, 2004-04-28 at 18:38, Guillermo Navarro wrote:
>> Hi,
>>
>> Thanks for your interest. I'm still working on it and as you said I
>> may find a way to encode the tags so I can use the existing tags (I'm
>> testing several approaches).
>>
>> At the moment I use a tag which looks like:
>>
>> (tag (my-kind-of-auth (index 3) (id 453455) (val <byte-string>)))
>>
>> It is an element of a hash chain. The "val" is an element "index" of
>> the hash chain "id".
>>
>> The intersection function, is something like: given two tags, the
>> resulting intersection is the one with a lower index, only if both
>> id's are equal, and we can verify the value of the corresponding hash,
>> otherwise the intersection is null.
>>
> As an idea, could the 'index' be a SetTag, where index 3 equates to
> (index (* set 1 2 3)). Therefore the intersection of (index (* set 1 2 3
> 4)) and (index (* set 1 2)) is (index (* set 1 2)).

Using SetTags won't scale well to large numbers of indexes.  Instead, you
can use a RangeTag to represent an arbitrarily large set:

Represent index N as (index (*range numeric lt N)), for example:
index 3 == (index (*range numeric lt 3))
index 1 == (index (*range numeric lt 1))

Then index 1 intersected with index 3 is the intersection of the ranges
"less than 1" and "less than 3", which is "less than 1".  (this is because
the "less than" parameter is an _upper limit_, and a lower upper limit is
more restrictive, and intersection returns the more restrictive range).


Note also that "only if both id's are equal" works fine as you have it:
(id 453455) will only intersect with another SimpleTag like (id 453455
...) -- the "..." is there because SimpleTags can be extended (and so
restricted), but this is irrelevant for what you're doing.


I agree with Sean about the (val ...) tag -- what value did you hash?

Sameer