Subject: [eman] Power interface in draft-ietf-eman-requirements-07.txt

From: "John Parello (jparello)" <[email-masked]>
Date: Wed, 4 Jul 2012 17:50:22 +0000

HI,

Thanks so much to the authors for the work on this.

One clarification I think is needed in the term Power Interface.  In the draft you have:

"""
Power Interface	
				
A Power Interface is an interface at which a device is connected	
to a power transmission medium at which it can receive power,	
provide power, or both.
"""

I think this definition is a bit of a tautology in that it defines a power interface as an interface. If you are indeed defining a Power Entity as a sub type or replacement to Energy Object  (see previous thread so herein Powered Entity or Energy Object are interchangeable)  then I would suggest a definition along the lines of what we reviewed  in the terminology. 

"Power Interface is an interconnection among Powered Entities...." is what I think you were trying to convey. I had "among" in the terms since clearly these interfaces can be split etc in some instantiation so between or connected seemed restrictive.

Two other points:

- I thought we agreed in the terminology and last meetings to use  Receive Energy and Provide Energy.  You went a bit loose on the interchangeable vernacular of power and energy.

- IMO the power transmission medium is not need. If so you'd need to define "power transmission medium" and I find no reference in our sources for such a term.

So I think you mean and would suggest a simpler

"Power interface is an interconnection among Powered Entities where energy can be provided, received or both" 

Jp

---

From: Juergen Quittek <[email-masked]>
Date: Wed, 4 Jul 2012 23:18:34 +0000

Hi John,

On 04.07.12 19:50, "John Parello (jparello)" <[email-masked]> wrote:

>I think this definition is a bit of a tautology in that it defines a
>power interface as an interface.

We define a "power interface" as an "interface at which ...". So, it's a
specialization of an interface, not a tautology.

>If you are indeed defining a Power Entity as a sub type or replacement to
>Energy Object  (see previous thread so herein Powered Entity or Energy
>Object are interchangeable)  then I would suggest a definition along the
>lines of what we reviewed  in the terminology.
>
>"Power Interface is an interconnection among Powered Entities...." is
>what I think you were trying to convey. I had "among" in the terms since
>clearly these interfaces can be split etc in some instantiation so
>between or connected seemed restrictive.

You bring us close to the point.

What I originally tried to ask for (and apparently did it in a poor way)
was a term for referring to "the things that are connected by power
interfaces".

The problem is that "Energy Object" cannot be used here, because a Power
Interface is an Energy Object by itself and Power Interfaces do not
connect Power Interfaces (or do they???)

There are two solutions to our problem:

1. We create a term for "things that power interfaces connect" (i.e.
devices or components of them).  The requirements draft uses "Powered
Entity", but this is not a good term and a better one is needed here.

2. We change our definition of "Energy Object" such that Energy Objects
are devices or components of them and Power Interfaces are something
different.

>Two other points:
>
>- I thought we agreed in the terminology and last meetings to use
>Receive Energy and Provide Energy.  You went a bit loose on the
>interchangeable vernacular of power and energy.

Yes, you are right.  This needs to be fixed.  Thanks for pointing it out.

>- IMO the power transmission medium is not need. If so you'd need to
>define "power transmission medium" and I find no reference in our sources
>for such a term.

You mean it's missing in the terminology section?  I thought the term was
descriptive enough to understand it without ambiguity.  But if you think
it is not clear, we can add it.

Whether or not the medium is needed depends on which media we want to
consider. 

I agree that if we consider only wire as transmission medium, we can
probably model everything without mentioning the medium.  We just need to
be able to support a power interface to be connected to multiple others.
The story changes if you use wireless energy transfer.  Then you will find
it hard to live with a model that ignores the medium.

>"Power interface is an interconnection among Powered Entities where
>energy can be provided, received or both"

Yes, much better.  Thanks.
Still I have the comments above.

    Juergen

> 
>
>
>Jp
>
>
>_______________________________________________
>eman mailing list
>[email-masked]
>https://www.ietf.org/mailman/listinfo/eman

---

From: Brad Schoening <[email-masked]>
Date: Wed, 4 Jul 2012 20:26:30 -0500

Juergen,

It's unfortunate that your response this question from John back on April
7th was delayed (3 months), as we would have benefited from having
discussed this earlier.

	"What I originally tried to ask for (and apparently did it in a poor way)
	was a term for referring to "the things that are connected by power
	interfaces".

Given a standard two-plug power outlet in the home or office;  I'm not
sure what the "power interface" is.  Each plug is connected to the same
bare wire conductor.  If I have a toaster on one and a PC on the other, I
may be only able to measure the PC's power consumption because it has an
internal meter. Hence the suggested use of "energy object".  I'm probably
missing something, but on shared conductors, I'm still struggling with how
"power interface" is applicable.

Regards,

Brad

---

From: Juergen Quittek <[email-masked]>
Date: Fri, 6 Jul 2012 22:54:49 +0000

Hi Brad,

Your case can easily be modeled without a power interface.
You just have the toaster and report its power or accounted energy.

If you want more details you may model the power interface of the PC.

    Juergen

---

From: Juergen Quittek <[email-masked]>
Date: Fri, 6 Jul 2012 22:54:52 +0000

Hi Brad,

>7th was delayed (3 months), as we would have benefited from having

It's unfortunate, that date formatting isn't the same all over the world.
I replied to John on the same day and not three months later.
So, you could benefit from an immediate response ;-)

It's just that this day, the 4th of July, in the US is formatted "7/4/12"
while in Germany we use "04.07.12".

It looks like you did only see my posting on that day and not Johns on
the same day on the mailing list.

Best regards,
    Juergen

---

From: Brad Schoening <[email-masked]>
Date: Sun, 8 Jul 2012 20:58:44 -0500

Hi Juergen,

I'm still a little confused by this terminology for "power interface" and
have a couple of questions:

	"Power Interface

	A power interface is an Energy Object that serves as a
	interconnection among Energy Objects, and participates in a
	Power Source Relationship."

1. Is a "power interface" a logical or physical entity?  I think it would
be good to clarify this in the definition.
2. As an interconnection, what knowledge, if any, does it have of it's
endpoint connections?  For example, if I unplug a PC and connect it to a
different plug, is the power interface changed?
3. Does the power interface know if carries AC or DC current?
4. If it's a physical entity, what components compose it; the plug, wire,
transformer, DC power distribuion?

Thanks,

Brad

On 7/6/12 6:54 PM, "Juergen Quittek" <[email-masked]> wrote:

>>>>One clarification I think is needed in the term Power Interface.  In
>>>>the
>>>>draft you have:
>>>>
>>>>"""
>>>>Power Interface	
>>>>

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Mon, 9 Jul 2012 08:29:44 +0200

> transformer, DC power distribuion?

draft-ietf-eman-requirements-07 (July 3, 2012):

   Powered Entity

      A Powered Entity is either a device or one of a device's
      components that is subject to energy monitoring or control or
      both.

   Power Interface

      provice power, or both.

Are you looking at an old document?

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>

---

From: Brad Schoening <[email-masked]>
Date: Mon, 9 Jul 2012 07:59:48 -0500

Juergen,

Great. Thanks for the updated reference, I was looking at the EMAN
Definitions document.  That adds some clarity, but I have the same basic
questions.

	1. Is a "power interface" a logical or physical entity?

	2. As an interconnection or interface, what knowledge, if any, does it
have of it's
	endpoint connections?  For example, if I unplug a PC and connect it to a
	different plug, is the power interface changed?

	4. If it's a physical entity, what components compose it; the plug, wire,
	transformer, DC power distribution?

Regards,

Brad