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The necessity of the Availability API

From: Rees, Kevron <kevron.m.rees@intel.com>
Date: Thu, 31 Jul 2014 09:46:50 -0700
Message-ID: <CAFW5wYYpwAAnmL61akz1oZBFNsp3-e-ckWixUjFfSS9NBLaLVw@mail.gmail.com>
To: "public-autowebplatform@w3.org" <public-autowebplatform@w3.org>
I'm continuing this previously private conversation on the public list.

The argument has been made that if there is to be an availability API,
that it should be at the attribute level.  Further, it has been argued
that it can only be at the attribute level.  It is not useful at the
interface level.

I agree with the argument.  However, I question the premise: that the
availability API is necessary at all.

To sum up my rationale, I'll make a couple arguments:

1 - The pattern is new to the W3C and overrides existing patterns
2 - availability adds unnecessary complexity to the API and developers
might not use it

1 - The availability API is an alien pattern to the w3c.  Attributes
on interfaces are typically marked with "?" (nullable mark) to imply
availability.  Take the geolocation API as an example[1]:

interface Coordinates {
readonly attribute double? altitude;

"The altitude attribute denotes the height of the position, specified
in meters above the [WGS84] ellipsoid. *If the implementation cannot
provide altitude information, the value of this attribute must be
null*." (emphasis mine)

2 - Given that we already make liberal usage of the nullable marker
(?), with the availability API we have effectively multiple ways of
discovering whether or not an attribute is provided.  Developers who
are accustomed to w3c patterns will likely use the former method and
ignore the availability API.  None of the applications we have in
Tizen at the moment will use the availability API.  It's hard to say
if application developers will use it or find it useful given the
already established pattern.

Possible objections:

"The Availability has advantages over the w3c pattern: it helps
developers understand why an attribute is unavailable."

I don't think we have a well-established use-case that justifies this
pattern.  Developers might only care if it's available or not and may
not care why.  We need to establish a better use-case if we want to

"It also notifies developers if that availability changes."

It is true a system *could* change the availability of an attribute
for numerous perceivable reasons.  This is true.  However, unless we
have a concrete example of a system that does this today or will in
the future, we are coding in assumptions that may never be realized.

I propose eliminating the availability API altogether and using "?" to
connotate availability as established by other w3c specifications.

Comments welcome,

[1] - http://dev.w3.org/geo/api/spec-source.html
Received on Thursday, 31 July 2014 16:47:22 UTC

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