[oslc-core] Oslc-Core Digest, Vol 11, Issue 23
Martin Nally
nally at us.ibm.com
Thu Dec 16 09:55:49 EST 2010
I don't think we should remove it, since it's already there, but I think
that in the future we should require a higher level of proof of both the
need and the value of a proposed solution before including things in the
spec. Adding more options to specs reduces the value of the spec and
increases the cost of adoption - the barrier for entry of new features
should be very high. To be honest, I think the core spec has too much.
Best regards, Martin
Martin Nally, IBM Fellow
CTO and VP, IBM Rational
tel: +1 (714)472-2690
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|12/15/2010 04:00 PM |
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|Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23 |
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Martin,
I used iPhone as an extreme case. I've seen many performance problems
caused by services returning too much data to browser and desktop clients.
When you examine these problems, they are usually caused by users using a
product in ways that the dev team did not expect or test. Some general
mechanism that allows clients to limit the amount of data returned seems to
be very well motivated by actual experience.
Paging is a standard solution to avoid sending all the data at once. Either
we allow the client to advertise its limits, or we require the server to
infer the limits based on other information such as the User-Agent. Are you
proposing an alternative to the current design, or just that it be dropped?
Regards,
___________________________________________________________________________
Arthur Ryman, PhD, DE (Embedded image moved to
file: pic29430.gif)
Chief Architect, Project and Portfolio Management
IBM Software, Rational
Markham, ON, Canada | Office: 905-413-3077, Cell:
416-939-5063
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|oslc-core at open-services.net, oslc-core-bounces at open-services.net |
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|12/14/2010 07:27 PM |
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|Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23 |
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I think the time to consider this would be when we had real experience from
iPhone implementers suffering a problem, and a prototype showing that this
is the simplest effective solution. It might seem like a good idea to
anticipate solutions to "obvious" potential problems, but my experience is
that this does not lead to good outcomes. Our ability to anticipate what
the problems will really be and imagine likely solutions is much less than
we think, and this sort of thinking leads to bloat and wasted effort on
problems that turn out not to matter, or solutions that don't work. This
sort of anticipation is what lean, Kanban and other popular methods tell
you not to do.
Best regards, Martin
Martin Nally, IBM Fellow
CTO and VP, IBM Rational
tel: +1 (714)472-2690
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|Arthur Ryman/Toronto/IBM at IBMCA |
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|Martin Nally/Raleigh/IBM at IBMUS |
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|oslc-core at open-services.net, oslc-core-bounces at open-services.net |
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|12/14/2010 06:35 PM |
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|Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23 |
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Martin,
"?oslc:pagesize=n" is useful for clients that have limited bandwidth or
processing ability. In practice, the size requested by a client is much
smaller than what the server could generate. For example, an iPhone might
request just 10 items per page whereas headless clients, such as ETLs or
crawlers, might request 1000 items per page.
Regards,
___________________________________________________________________________
Arthur Ryman, PhD, DE (Embedded image moved to
file: pic38423.gif)
Chief Architect, Project and Portfolio Management
IBM Software, Rational
Markham, ON, Canada | Office: 905-413-3077, Cell:
416-939-5063
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|Martin Nally/Raleigh/IBM at IBMUS |
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|Arthur Ryman <ryman at ca.ibm.com> |
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|oslc-core at open-services.net, oslc-core-bounces at open-services.net |
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|12/10/2010 11:36 AM |
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|Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23 |
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Yes, makes sense. See a separate note where I asked why we have
"?oslc:pagesize=n". That is the only place I know where there is any
suggestion that pages might be equal-sized. I'd be happy to get rid of
that.
Best regards, Martin
Martin Nally, IBM Fellow
CTO and VP, IBM Rational
tel: +1 (714)472-2690
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|Arthur Ryman <ryman at ca.ibm.com> |
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|Martin Nally/Raleigh/IBM at IBMUS |
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|oslc-core at open-services.net, oslc-core-bounces at open-services.net |
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|12/10/2010 10:20 AM |
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|Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23 |
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Martin,
The point that was bothering me was that it might be a burden on
implementations to require that the number of pages and the RDF triples in
each page are the same for all representations.
For example, suppose an implementation imposes a limit of 1 MB per page.
Suppose in Turtle you can pack 10,000 triples per MB, but in HTML you can
only pack 1,000 triples per MB. Suppose a resource has 2,000 triples. The
server could return then all in 1 page of Turtle, but would require 2
pages of HTML. I am suggesting we allow that. Does that fit with your
view?
Regards,
___________________________________________________________________________
Arthur Ryman, PhD, DE
Chief Architect, Project and Portfolio Management
IBM Software, Rational
Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063
From:
Martin Nally <nally at us.ibm.com>
To:
oslc-core at open-services.net
Cc:
oslc-core at open-services.net, oslc-core-bounces at open-services.net
Date:
12/09/2010 03:30 PM
Subject:
Re: [oslc-core] Oslc-Core Digest, Vol 11, Issue 23
Sent by:
oslc-core-bounces at open-services.net
I agree with what you wrote, but it doesn't seem to contradict what I
said.
There is something slightly comic about this conversation. I think you
provided a very clever insight that both simplifies and generalizes the
concept of paging, and now you seem to be arguing against your own clever
idea. I was worried that it was conceptually difficult to define what it
means to return the first half (or third, or quarter) of an HTML
representation. Your insight is that you do not have to worry about that -
you can define pagination in terms of the underlying RDF resource. There
are some minor complexities in "paginating" an RDF resource that has blank
nodes - all triples that reference the same blank node need to appear on
the same "page" - but otherwise paginating an RDF resource is conceptually
trivial. Representing those pages is now well defined - all you need is a
valid HTML, JSON, RDF/XML, Turtle or other representation of the page,
which is itsefl a well-defined RDF resource. No special specification or
documentation is required. It's a very simple, elegant model - go to the
top of the class. A server that is paginating a resource for HTML
representation is free to define the pages in a way that is convenient for
HTML display, as you point out below.
Best regards, Martin
Martin Nally, IBM Fellow
CTO and VP, IBM Rational
tel: +1 (714)472-2690
>
> Martin,
>
> Although any resource may have multiple representations, some resources
> may only have one representation. In the case of paging, I think it
makes
> sense to allow the page contents and breaks to depend on the
> representation initially selected. Different representations will differ
> in their compactness, e.g. one page of Turtle might take 10 pages of
HTML.
>
> Regards,
>
___________________________________________________________________________
>
> Arthur Ryman, PhD, DE
>
> Chief Architect, Project and Portfolio Management
> IBM Software, Rational
> Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063
>
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