Re: Temporal database - no end date
From: Volker Hetzer <firstname.lastname_at_ieee.org>
Date: Mon, 22 Jan 2007 18:26:42 +0100
Message-ID: <ep2s4i$755$2_at_nntp.fujitsu-siemens.com>
>
> Suppose I have 5 things. 4 of them lasted for 1 'day' before they
> break.The other broke on the same 'day' it went out.
>
> What is the mean time to failure?
>
> Sum of 'time quanta' = 4.
> Number of things = 5.
>
> Mean time to failure = 0 time quanta.
>
> Pick any intuitive unit of 'time quanta', and you can construct an
> example where this problem arises.
I'm not really sure what's wrong with it. All it shows is that you have chosen the wrong granularity for the job. Your "pick any" sentence simply states that for any real world scenario you can choose the wrong granularity if you insist.
Date: Mon, 22 Jan 2007 18:26:42 +0100
Message-ID: <ep2s4i$755$2_at_nntp.fujitsu-siemens.com>
DBMS_Plumber schrieb:
> V.J. Kumar wrote:
>> Could you show with an example how the loss occurs ? You may be right, but >> let's see.
>
> Suppose I have 5 things. 4 of them lasted for 1 'day' before they
> break.The other broke on the same 'day' it went out.
>
> What is the mean time to failure?
>
> Sum of 'time quanta' = 4.
> Number of things = 5.
>
> Mean time to failure = 0 time quanta.
>
> Pick any intuitive unit of 'time quanta', and you can construct an
> example where this problem arises.
I'm not really sure what's wrong with it. All it shows is that you have chosen the wrong granularity for the job. Your "pick any" sentence simply states that for any real world scenario you can choose the wrong granularity if you insist.
Lots of Greetings!
Volker
-- For email replies, please substitute the obvious.Received on Mon Jan 22 2007 - 18:26:42 CET