W3C home > Mailing lists > Public > public-geolocation@w3.org > August 2009

Re: Comment on Geolocation API Specification: maximumAge and timeout

From: <noah_mendelsohn@us.ibm.com>
Date: Mon, 24 Aug 2009 11:03:42 -0400
To: Doug Turner <doug.turner@gmail.com>
Cc: Becky_Gibson@notesdev.ibm.com, jferrai@us.ibm.com, "Thomson, Martin" <Martin.Thomson@andrew.com>, Patrick_Mueller@us.ibm.com, public-geolocation@w3.org
Message-ID: <OFFE736DA3.574505AE-ON8525761C.0051BC05-8525761C.00526932@lotus.com>
Doug Turner:

> I think that the argument that I recall and agreed with was that some 
> of these features could be implemented in a higher-level JS library.

Indeed.  The questions I was raising are:

* Will performance be acceptable.  Note that the API provides no bound at 
all on the frequency of upcalls.  An implementation that called 1000x per 
second would be conforming.  I think you need to at least give 
implementors some guarantee on what the rates will be, or else you can't 
tell if you're building an application that will behave acceptably.  To 
even find a path into a browser, activate a Javascript method, and have 
that (user provided) method return of the interval is too short has an 
overhead on constrained devices.  What will happen if several applications 
are tracking location simultanously>

* In terms of making the API useful, you're asking users who care to 
re-implement that timing logic in each application.  It's not hard, but 
it's duplicate work, and needs to be debugged (timing dependent code can 
be tricky to test).  So, I think there's some incremental value in having 
the API do it.  Whether there's enough value to justify the additional 
specification complexity, implementation in user agents, disruption to 
existing deployments, I can't say for sure.

Bottom line:  I think the spec should at least say something useful about 
the rate of updates, with the goal of letting users understand what rates 
of call they need to plan for (keeping in mind that users will worry both 
about updates that don't happen often enough, and those that might happen 
too often).  My intuition is that the spec would be better if the user 
could at least give some guidance on desired update rates through the 
APIs, but I can't prove conclusively that it's worth the trouble to do 
that.

Thanks in any case for considering my comments.

Noah

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------








Doug Turner <doug.turner@gmail.com>
08/23/2009 10:18 PM
 
        To:     "Thomson, Martin" <Martin.Thomson@andrew.com>
        cc:     <noah_mendelsohn@us.ibm.com>, <public-geolocation@w3.org>, 
<Becky_Gibson@notesdev.ibm.com>, <jferrai@us.ibm.com>, 
<Patrick_Mueller@us.ibm.com>
        Subject:        Re: Comment on Geolocation API Specification: 
maximumAge and timeout



On Aug 23, 2009, at 5:15 PM, Thomson, Martin wrote:

> Noah's comments are quite significant in addressing some basic 
> usability and interoperability considerations.  Control over the 
> rate of notifications is important.


Control over the rate of notification and/or notification based on 
moving x distance can easily be built in web content javascript via an 
interval.  I believed we discussed this at some, but there isn't a 
tracker item for it.  Nor do I find anything on the mailing list 
search.  Could it have been at the f2f?  (unfortunately, i only recall 
the geopriv debate).

I think that the argument that I recall and agreed with was that some 
of these features could be implemented in a higher-level JS library.


Doug Turner
Received on Monday, 24 August 2009 15:02:13 UTC

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