Hello Costas, I thought about this for time. My point of view is the following: I can use my calendar application and define appointments for "every day from now until next Friday, 9am-5pm". After entering this appointment and going to the calendar view, I see one appointment each day. So "every day from now until next Friday, 9am-5pm" was just an intensional description of what can be expressed by an extensional description as well (see http://en.wikipedia.org/wiki/Intensional_definition). So what are the advantages and disadvantages of an intensional description? 1) Positive: compact representation 2) Negative: difficult to model, negotiate and evaluate adherence 3) Positive: can be used to model infinite number of repetitions (every day until the end of the world) I think that 3) has no real usecase as contracts should contain a well defined end. Considering 1) and 2) I am still in favor of the extensional description. "every day from now until next Friday, 9am-5pm" becomes just "2009/12/10 9am-5pm, 2009/12/11 9am-5pm, ..., 2009/12/18 9am-5pm". When the user enters an SLA its GUI can still present "every day from now until next Friday, 9am-5pm" but just render it as an extensional set. Each individual time frame could be modeled as one SDT+GT. I think the extensional description has the same expressiveness (as mentioned, I don't see 3) as a usecase for us) but is easier to handle and creates a leaner specification. Best regards, Dominic On 12/07/2009 05:17 PM, Constantinos (Costas) Kotsokalis wrote:
Hi Dominic,
Recurring patterns for service usage is something that is needed in many cases, even if not allowed by current technology/service providers. In an example scenario where someone rents VMs to execute enterprise operations s/w on them, (s)he would certainly prefer to load-balance over a number of them available during working hours, and half or less that number outside working hours, to save money. I know this is not something that current cloud providers offer (to the extent I'm aware of, at least) but I believe it's a realistic need, and fits with fully dynamic scaling scenarios.
On the same time, I do agree that it increases complexity, especially if one is willing to include constructs such as "on the first Monday of every month" etc.
Just my E0.02.
Best regards,
Costas
On 7 Dec 2009, at 14:39, Dominic Battre wrote:
Hello Costas,
it would certainly be a possible extension.
The question is do we want it? If we end up translating ical to XML we come to a specification that is extremely powerful but very difficult to implement.
Our idea was to use the simplest language that would be useful. Therefore, I would like to ask you and the others: Do you need something like "every day, 9am-5pm"?
Best regards,
Dominic
Constantinos (Costas) Kotsokalis wrote:
Hi Dominic, Would you see fit to augment this also with some construct for defining periodic durations? E.g. to be able to say "every day, 9am-5pm", or things like that. Best regards, Costas On 7 Dec 2009, at 13:43, Dominic Battre wrote:
Dear GRAAP members,
we have seen in various discussions that there seems to be a frequent desire for a standardized term language to express when a service shall be delivered.
Examples are:
- Making a hardware reservation of a cluster for interactive use
- Co-allocation of resources of various types (hardware, network, licenses, ...)
- Defining a deadline for the completion of a job
We have had a discussion about this in Banff after which Oliver and I have prepared a proposal for a Time Constraints Profile for WS-Agreement. This proposal has been uploaded here:
https://forge.gridforum.org/sf/go/doc15832?nav=1
We would be eager to hear your comments.
- Is the proposal clear?
- Is the proposal complete?
- Does the proposal satisfy your needs?
Best regards,
Dominic -- graap-wg mailing list graap-wg@ogf.org http://www.ogf.org/mailman/listinfo/graap-wg