Abstract
This specification standardizes a packaging format for a class of
software application known as a widget. Widgets are client-side
applications that are authored using Web standards, but whose content can
also be embedded into Web documents. The specification relies on PKWare's
Zip specification as the archive format, XML as a configuration document
format, and a series of steps that runtimes follow when processing and
verifying various aspects of a package. The packaging format acts as a
container for files used by a widget. The configuration document is an XML
vocabulary that declares metadata and configuration parameters for a
widget. The steps for processing a widget package describe the expected
behavior and means of error handling for runtimes while processing the
packaging format, configuration document, and other relevant files. This
document also defines expected behavior for conformance checkers, which
are tools that aid authors in verifying that Zip archives and
configuration documents conform to this specification.
This specification is part of the Widgets 1.0 family of
specifications, which together standardize widgets as a whole.
Status of this Document
This section describes the status of this document at the time of
its publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the W3C technical reports
index at http://www.w3.org/TR/.
This is the 1 July 2009 Candidate Recommendation of the
Widgets 1.0: Packaging and Configuration specification. W3C publishes a
Candidate Recommendation to indicate that the document is
believed to be stable and to encourage implementation by the developer
community. The Web Applications (WebApps) Working Group expects to
request that the Director advance this document to Proposed
Recommendation once the Working Group has developed a comprehensive
Widgets 1.0: Packaging and Configuration test suite, and demonstrated at
least two interoperable implementations. The WebApps Working Group
expects to show these implementations by September 2009. The Working
Group does not plan to request to advance to Proposed Recommendation
prior to 01 September 2009.
This document is produced by the Web Applications WG, part of
the Rich Web Clients
Activity in the W3C Interaction Domain. It is
expected that this document will progress along the W3C's Recommendation
track. Publication as a Candidate Recommendation does not imply
endorsement by the W3C Membership. This is a draft document and may be
updated, replaced or obsoleted by other documents at any time. It is
inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February
2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in
connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains Essential
Claim(s) must disclose the information in accordance with section
6 of the W3C Patent Policy.
You can find the latest Editor's Draft of this
document in the W3C's CVS repository,
which is updated on a very regular basis. The public is
encouraged to send comments to the Web Apps Working Group's public
mailing list public-Webapps@w3.org (archive).
See W3C mailing list and archive usage
guidelines. A detailed list of changes
from the previous version is also available from the W3C's CVS server.
Table of Contents
1
Introduction
Widgets are full-fledged client-side applications that are
authored using Web standards and packaged for distribution. They are
typically downloaded and installed on a client machine or device where
they run as stand-alone applications, but they can also be embedded into
Web pages and run in a Web browser. Examples range from simple clocks,
stock tickers, news casters, games and weather forecasters, to complex
applications that pull data from multiple sources to be "mashed-up" and
presented to a user in some interesting and useful way (see [Widgets-Landscape] for more information).
1.1
Design Goals and Requirements
1.2 How This Document is Organized
This section is non-normative.
The reader should be aware that this document is organized into two
halves, but not explicitly marked as such. The first half defines the
various aspects of what constitutes the packaging format, the configuration document, and reserved files, such as default icons
and locale folders,
as well as some of the expected behavior of conformance
checkers, which are implementations that check the conformance of a
Zip archive or a configuration document to this
specification. Where possible, the first half avoids describing aspects
related to processing, which are described in detail in the second half
of the document.
The second half, which starts with the section titled "Steps for Processing a
widget package", defines the steps required to process a widget
package as well as the expected behavior of a user agent as it processes
the packaging format, the configuration document, and attempts to find
localized content. The second half of this document also deals with error
handling in the event that a user agent encounters unsupported or missing files, or DOM nodes that are in error in the configuration document. Wherever
processing is relevant, sections in the first half of the document link
to sections in the second half of the document.
1.3
Typographic Conventions
This section is non-normative.
Defined terms appear as this sample
defined term. Such terms are referenced as sample defined term, providing a link
back to the term definition.
Words that denote a conformance clause or testable assertion use
keywords from [RFC2119]: MUST,
MUST NOT, Required, SHOULD, SHOULD NOT, RECOMMENDED, MAY and OPTIONAL.
Variables are formatted specially, e.g. variable. Code is
also specially formatted, such as code.
Words in italics denote a
formal definition given in an external specification.
This is an example. Examples are used to explain
concepts or demonstrate how to use a feature.
ISSUE: This is an issue. It implies something
that Working Group is trying to fix. Eventually, all these will disappear
from the spec.
Note: This is a note, it
usually contains useful supplementary information in a non-normative
form.
Authoring guideline:This is an
authoring guideline. Its purpose is to provide authors with best-practice
authoring techniques.
This is an editorial note. It denotes something
that the editor is working on or some rough notes. The reader should
ignore these! Eventually, all these will disappear from the spec.
This section is non-normative.
This specification is part of the Widgets 1.0 family of
specifications, which together standardize widgets as a whole.
The Widgets 1.0: APIs and Events [Widgets-APIs] specification defines APIs to store
preferences and capture events. The Widgets 1.0: Digital
Signature [Widgets-DigSig]
specification defines a means for widgets to be digitally signed using a
custom profile of the XML-Signature Syntax and Processing
Specification. The Widgets: 1.0: Automatic Updates [Widgets-Updates] specification defines a
version control model that allows widgets to be kept up-to-date over [HTTP]. The Widgets 1.0: Access Requests [Widgets-Access] specification allows authors
to request access to URI-identifiable resources (e.g. resources on the
Web).
1.5
Definitions
The following definitions are used throughout this specification.
Please note that other terms are given throughout this document and
defined where they are used.
An author is a person who created a widget package or an authoring tool that
generated a widget package.
A media type is defined in the [MIME] specification (see in particular RFC2046).
A language tag is a text
string that matches production of a Language-Tag defined in
the [BCP47] specifications. It is optional for user agents to validate language tags
against the IANA
Language Subtag Registry.
A widget is defined by the [Widgets-Landscape] as an end-user's
conceptualization of an interactive single purpose application for
displaying and/or updating local data or data on the Web, packaged in a
way to allow a single download and installation on a user's machine,
mobile phone, or Internet-enabled device
. Because widgets are
packaged, they can be shared by users without relying on [HTTP] (i.e., users can share widgets over non-HTTP
distribution channels, such as Bluetooth or a USB thumb drive).
Reserved means that a character, or text
string, or file-name, or folder-name has a specified purpose and
semantics in this specification or in some other specification or system.
The intended purpose for any reservation is given when the term is used.
Arbitrary means that a character, or text
string, or file-name, or folder-name is not reserved for the purpose of this specification.
Supported means that a user agent implements
a mentioned specification, or conformance clause, or is able to process
or otherwise render mentioned media type.
- Unsupported means the user agent does not
implement a mentioned specification, or feature,
or is unable to render or otherwise process a mentioned media type.
Initialization means a run through the
steps for processing a widget package after installation of a widget.
1.5.1
Character Definitions
The space
characters, for the purposes of this specification, are [Unicode] code points:
- U+0020 SPACE,
- U+0009 CHARACTER TABULATION (tab),
- U+000A LINE FEED (LF),
- U+000B LINE TABULATION,
- U+000C FORM FEED (FF),
- U+000D CARRIAGE RETURN (CR).
The Unicode white space
characters are are [Unicode] code points
marked in the [Unicode] specification (version
5.0.0) with the property "White_Space".
The control characters, for the
purpose of this specification, are [Unicode] code
points:
- U+0000 NUL–U+001F INFORMATION SEPARATOR 1,
- U+007F DELETE.
The following Unicode code points are referred to as the forbidden characters in this
specification:
- The control characters,
- U+003C LESS-THAN SIGN,
- U+003E GREATER-THAN SIGN,
- U+003A COLON,
- U+0022 QUOTATION MARK,
- U+002F SOLIDUS,
- U+005C REVERSE SOLIDUS,
- U+007C VERTICAL LINE,
- U+003F QUESTION MARK,
- U+002A ASTERISK,
- U+005E CIRCUMFLEX ACCENT,
- U+0060 GRAVE ACCENT,
- U+007B LEFT CURLY BRACKET,
- U+007D RIGHT CURLY BRACKET,
- U+0021 EXCLAMATION MARK.
As well as sections marked as non-normative, all authoring guidelines,
diagrams, examples, and notes in this specification are non-normative.
Everything else in this specification is normative.
The key words must, must not,
Required, should, should not, recommended, may and optional in this
specification are to be interpreted as described in [RFC2119].
This specification describes the conformance criteria for user agents
(relevant to implementers) and various resource types (relevant to
authors).
There are four classes of products that can claim conformance to this
specification:
- A user agent.
- A widget package.
- A configuration document.
- A conformance checker.
While a conforming user agent may support other
legacy/proprietary widget types in order to conform to this
specification, a user agent must treat widget
packages as according to this specification.
3 User Agents
A user agent is an implementation that supports this specification.
Note: The user agent
described in this specification does not necessarily denote a "widget user agent" at large: that is, a user
agent that implements all the specifications, and dependencies, defined
in the Widgets 1.0: Family of Specifications. The user agent described is
this specification is only concerned with how to processes Zip archives and configuration documents.
A user agent must behave as described by this
specification in order to claim conformance, even when faced with a
non-conforming widget package or a
non-conforming configuration documents.
Note: Implementers can
partially check their level of conformance to this specification by
successfully passing the test cases of the [Widgets-Test-Suite]. Note, however, that
passing all the tests in the test suite does not imply conformance to
this specification; It only implies that the implementation conforms to
aspects tested by the test suite.
ISSUE: test-suite is not done yet, it will be
completed when we go to Candidate Recommendation.
3.1 Dependencies on Other Specifications and File
Formats
3.2 Internationalization Tag Set Support
This feature is at risk.
To facilitate the localization of text nodes within XML elements in a
configuration document, a user
agent MAY support the Internationalization Tag Set's ([ITS]) its:span element and the
its:dir attribute. It is optional for a
user agent to support other
ITS elements and attributes.
Although this specification defines the elements of the configuration document in which
its:span element and the its:dir attribute can
be used (below), the specification does not define how they are to be
interpreted and processed by a user agent. If a user agent implements
its:span and its:dir, then the user agent must do so in conformance to the processing rules defined
by the [ITS] specification.
A conformance checker (CC) is a user agent that verifies whether a widget package and a configuration document conform to
this specification. A CC checks the conformance of either a widget package or a configuration document by
implementing the assertions made in sections labeled conformance
checker behavior throughout this document.
In those sections, this specification asks CCs to inform authors of conformance violations, which means
they display advisory messages to authors in a manner that assists them
in making their widgets valid and conforming. Wording of advisory
messages is left to the discretion of implementers. It is optional for a CC to display all messages at once.
5 Zip Archive
The packaging format for the files of a widget is the Zip archive format as defined in the [ZIP] file format specification.
A file entry is the data held by a , file data, and (optional) data descriptor, as defined
in the [ZIP] specification, for each physical file
contained in a Zip archive.
A potential Zip archive is a data
object that has not been verified to be a valid Zip archive.
A valid Zip archive is a data object
that conforms to the production of a .ZIP file as defined by the Zip File Format
Specification [ZIP], with the exclusion or support for the features and
conditions defined in the Zip Support
section.
Note: Step 2 of the steps for processing a
widget package describes how user agents verify that a Zip archive
conforms to this specification.
The magic numbers for a Zip
archive is the byte sequence: 50 4B 03 04.
To conform to this specification, a Zip
archive must contain one or more file entries and must be a valid Zip
archive.
Note: A valid Zip archive
does not imply a conforming widget package.
All valid Zip archives need to be further checked, using Step 2, to see if they qualify as a widget package.
5.1
Compression Methods
5.3 Zip
Relative Paths
A Zip relative path is the
variable-length string derived from the file name field of the local file header of a file entry.
Note: A Zip relative path
is said to be relative as it stores the string that represents file and
folder names relative to where the Zip archive was created on a file
system (e.g. images/bg.png), as opposed to storing an
absolute path (e.g. c:\images\bg.png). The value of a Zip
relative path will generally resemble the string value of a name of the
file or folder(s) on the device on which the Zip archive was created, but
with the exception of the path delimiter being a U+002F SOLIDUS "/"
character. Note also that a Zip relative path is not a URI reference; Zip
relative paths need to be converted to URI references before they can be
used in context that make use of URIs.
The valid encodings for a Zip relative
path are either [CP437] or [UTF-8]. It is recommended that the
file name field be encoded
using [UTF-8].
For interoperability, manipulations of Zip relative paths must be performed on the string obtained by decoding the
file name field using the
appropriate encoding, and not on the bytes initially stored in the
archive. For the sake of comparison and matching, it is recommended that a user agent internally treats all
Zip-relative paths as [UTF-8].
A valid Zip relative path is
one that case-insensitively matches the production of Zip-rel-path in the following [ABNF]:
zip-rel-path = [ *folder-name ] file-name /
[ locale-folder ] 1*folder-name /
locale-folder [ *folder-name ] file-name
locale-folder = "locales" "/" folder-name
folder-name = file-name "/"
file-name = base-name [ file-extension ]
base-name = 1*allowed-char
file-extension = "." 1*allowed-char
allowed-char = safe-char / utf8-char
safe-char = ALPHA / DIGIT / SP / "$" / "%"
/ "'" / "-" / "_" / "@"
/ "~" / "(" / ")" / "&" / "+"
/ "," / "." / "=" / "[" / "]"
utf8-char = %x80-D7FF / %xF900-FDCF / %xFDF0-FFEF
/ %x10000-1FFFD / %x20000-2FFFD / %x30000-3FFFD
/ %x40000-4FFFD / %x50000-5FFFD / %x60000-6FFFD
/ %x70000-7FFFD / %x80000-8FFFD / %x90000-9FFFD
/ %xA0000-AFFFD / %xB0000-BFFFD / %xC0000-CFFFD
/ %xD0000-DFFFD / %xE1000-EFFFD
Note that ALPHA,
DIGIT, and SP are defined in the [ABNF] specification (but essentially represent
alphanumerical characters and the U+0020 SPACE code point respectively).
This specification does not put a restriction on the byte length of a
Zip relative path, so a user agent must be able to deal with path lengths longer than 250
bytes.
Authoring guideline:
Authors need to keep path lengths below 250 bytes. Unicode code points
may require more than one byte to encode a character, which can result
in a path whose length is less than 250 characters but whose size is
greater than 250 bytes.
In addition, in the case where the Zip relative path is encoded using
[UTF-8], the language encoding flag (EFS) needs
to be set.
Authors need to be aware that, at the time of writing, there are some
interoperability issues with regards to using characters outside the
safe-chars range for file or folder names in a Zip archive.
If an author chooses to use cp437-chars or the
utf8-chars, they should thoroughly test their widgets on
various platforms prior to distribution; otherwise it is suggested that
authors restrict file and folder names to the safe-chars
(characters in the US-ASCII range). In addition, having excessively long
path names (e.g. over 120 characters) can also result in
interoperability issues on some operating systems.
A CC must inform the author
about any file entry whose file name field does not match the
production of a zip-rel-path.
A CC must inform the author
of any Zip relative path whose length exceeds 120 characters.
5.4
Disallowed Characters
Forbidden characters must not appear anywhere in the file-name.
A user agent must ignore a file that
contain forbidden characters in the
Zip relative path.
Note: These characters are
reserved to maintain interoperability across various file systems and
with [URI]s.
Authoring Guideline: Avoid using the following words
as either a folder or a base-name in a Zip relative path as they are reserved by
some operating systems (case-insensitive): CON, PRN, AUX, NUL, COM1,
COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4,
LPT5, LPT6, LPT7, LPT8, LPT9, CLOCKS$. For example, the following names
are ok: "CON-tact.txt", "printer.lpt1", "DCOM1.pdf". However, "com3.txt"
"Lpt1", "CoM9.gif" would not be.
In addition, also avoid having a "." U+002E FULL STOP as the last
character of a file or folder name as some operating systems will remove
the character when the file is extracted from the Zip archive onto the
device. Furthermore, avoid having the space character (SP) at the start or end of a file name; and take caution
when using the "+" U+002B PLUS SIGN, as it might cause issues on some
operating systems.
A CC must inform the author of the
presence of any of the reserved characters in a file-name.
A CC should inform the author of the
presence of a U+0020 SPACE character at the start or end of a file-name.
A CC should inform the author of the
presence of any U+002E FULL STOP at the end of a file-name.
A CC should inform the author of any
base-name that case-insensitively
matches any of the following strings: CON, PRN,
AUX, NUL, COM1, COM2,
COM3, COM4, COM5,
COM6, COM7, COM8,
COM9, LPT1, LPT2,
LPT3, LPT4, LPT5,
LPT6, LPT7, LPT8,
LPT9, CLOCKS$.
A CC may inform the author of the
presence of any U+002B PLUS SIGN in a file-name.
A widget package must
be a valid Zip archive that contains:
Note: See step 1 - Acquire a Potential Zip Archive for
instructions on how to process a widget package.
6.2
Files and Content Types
The root of the widget
package is the top-most path level of the Zip archive. The root of the widget package
contains files and folders, some of which are reserved (see reserved file names and reserved folder names).
A file is the decompressed physical representation
of a file entry (i.e., a file extracted into its
physical form as it was prior to being added to the Zip archive).
Note: Unlike [HTTP] resources, file entries within a Zip archive
are not available in multiple representations, nor are files dynamically
generated from URI query parameters when the use agent retrieves them from
within a Zip archive.
A folder is a file
entry whose file name field
matches the production of folder-name in a valid Zip relative path (the last
character of the file name field
is a U+002F SOLIDUS) and whose version needed to extract is
2.0.
A folder may contain zero or
more file entries or zero or
more folders.
File-extension to
media-type mapping is the process whereby a user agent maps the
file-extension of a file to a media type.
Content-type sniffing is the
process of determining the media type of a file
by examining the initial bytes of a file for
standardized sequence of bytes known as magic
numbers (e.g. the byte sequence 47 49 46 38 37 61,
which is the signature for a GIF89a image file format). The patterns used
by this specification have all been standardized with the Internet Assigned Numbers Authority
(IANA), as part of a media type registration.
As there is no notion of a media type within
Zip, a user agent must perform file-extension to media-type
mapping, followed by content-type
sniffing, in order to determine the media
type of a file.
For sniffing the content type of images formats, a user agent must use the rule for Identifying the
media type of an image. For other file formats, a user agent must use the rule for Identifying the
media type of a file.
A processable file is a file that:
6.3 Reserved File and Folder Names
The reserved file names table,
below, contains a list of file names that are reserved for some purpose by this specification. The
file names of the first column of the reserved file names table must be treated as case-sensitive.
The [Widgets-DigSig] specification also
defines the naming
conventions for a distributor signature and the naming
convention for an author signature. The names of those files are also
reserved for the purpose of this specification.
The reserved folder names table,
below, contains a list of folder-names that are reserved for some purpose by this specification. All
reserved folder names must be treated as
case-sensitive.
6.4
Digital Signatures
A widget package contains a digital signature, and hence is digitally signed, if the widget package
contains one or more files that conform
to the [Widgets-DigSig] specification. The
file naming convention for digital signatures files is defined in the [Widgets-DigSig] specification.
A user agent must prevent a browsing context of a
widget from accessing (e.g., via scripts, CSS, HTML, etc.) the contents of
a digital signature document unless an access control mechanism explicitly
enables such access, e.g. via a an access control policy. The definition
of such a policy mechanism is beyond the scope this specification, but may be defined to allow access to all or parts of the
signature documents, or deny any such access. An exception is if a user
agent that implements this specification also implements the optional [Widgets-DigSig]
specification, in which case the user agent must make
signature documents available to the implementation of the [Widgets-DigSig] specification.
6.5 Start
Files
The start file of a widget package is a file
that is used by the user agent when the widget is instantiated. This
specification defines two kinds of start file: custom start file and default start file.
6.5.1
Custom start file
A custom start file is a start file identified via a content element's src attribute. The custom start file must be a processable file
inside the widget package, determined by
applying the rule for
identifying the media type of a file. When a start file is not explicitly declared via the content element,
then start file will be one of the default start
files.
6.5.2
Default Start File
A default start file is a reserved start file whose
file name case-sensitively and exactly matches a file name given in the
file name column of the default start
files table, and whose media type matches
the media type given in the media type column
of the table.
A default start file must appear at either the root of the widget package or at
the root of a locale folder.
If a user agent encounters a file matching a file
name given in the file name column of the default start files table in an arbitrary folder, the user
agent must treat that file as an arbitrary file. For example,
"foo/bar/index.html" would be treated as an arbitrary file.
Default Start Files
Table
| file name |
media type |
| index.htm |
text/html |
| index.html |
text/html |
| index.svg |
image/svg+xml |
| index.xhtml |
application/xhtml+xml |
| index.xht |
application/xhtml+xml |
It is optional for user agents to support the media types listed in the default start files table.
Note: See Step 8 for instructions on finding a default start file.
Authoring guideline: Always include
at least one start file in a widget package.
A CC must verify that the widget package contains at least one start file by:
- Checking within the configuration document for a correct
content element to point to a processable file within the widget package.
- Checking for the presence of a default
start file at the root of the
widget package and in all locale folders.
If the widget package does not contain a start
file, or the start file is not one that is supported by a particular user agent, then the CC
must inform the author.
6.6 Icons
An icon is an optional file that is used to represent the widget in various
application contexts (e.g. the icon that the user actives to instantiate a
widget, or an icon in a dock or task bar or some other visual context).
The icon is intended to help users of visual browsers to recognize the
widget at a glance. There are two kinds of icons defined by this
specification, custom icons and default icons.
6.6.1
Custom Icons
A custom icon is an icon
explicitly declared to be used as an icon by an author via an icon element of the configuration document. The media type of a custom icon is derived by the rule for identifying the
media type of an image.
A custom icon can be located either at the root of the widget package, or at
the root of a locale folder, or in an
arbitrary folder.
6.6.2
Default Icons
A default icon is a reserved icon whose file name
case-sensitively and exactly matches a file name given in the file name
column of the default icons table.
A default icon must be
located either at the root of the
widget package or at the root of a locale
folder.
Default Icons Table
| file name |
media type |
| icon.svg |
image/svg+xml |
| icon.ico |
image/vnd.microsoft.icon |
| icon.png |
image/png |
| icon.gif |
image/gif |
| icon.jpg |
image/jpeg |
A user agent must derive the media type of a default
icon from the media type column of the default icons table.
A user agent must search for a default icon's
file-name based on the order they
appear in the default icons table (from
top to bottom).
Implementations that support
the use of [SVG] as an icon format
may display declarative animation. However, for
security reasons, a user agent must not execute
scripts or interactivity defined within an [SVG] icon
file. Animation and interactivity is defined as the set of features
intended for use of SVG as a dynamic image, corresponding to the [SVGTiny] profile, and to specific feature strings:
- [SVG]
http://www.w3.org/TR/SVG11/feature#SVG-static- [SVGTiny12]
http://www.w3.org/Graphics/SVG/feature/1.2/#SVG-animated
Authoring guideline: If using [SVG] as an icon format, and the intention is for it to be
animated, then use declarative animation. Also, avoid creating icons that
depend on scripts for animation and interactivity.
If no default icon has been included, and
the CC determines that no custom icons have been declared in the configuration document, a CC MUST inform the author that it is desirable,
but optional, to include a default icon.
If a CC encounters an icon in the [SVG] format, the
CC may inform the author if the
icon includes script or interactive functionality.
If a CC encounters an icon in a format other than [PNG] or [GIF89] or [GIF87], then the CC should inform the
author that these formats might not be supported
on all user agents.
If a CC encounters an icon in the [SVG] format, then
the CC must inform the author if
the icon does not conform to the [SVGTiny]
specification.
The widget media type is
application/widget [MIME].
Authoring guideline: If the
protocol over which the widget package is
transferred supports the
[MIME] specification, then Make sure that the widget is labeled with an
application/widget media type. Failure to correctly label a
widget package will result in it being
treated as an invalid Zip archive.
ISSUE: The
application/widget media type has not yet been registered
with IANA. This will happen when the
specification reaches Candidate Recommendation status.
6.8 File
Extension
A widget file extension is the
text string that case-insensitively matches the string ".wgt"
any case form (e.g. .wgt, .WGt,
.WgT, etc. are all valid).
The widget file extension is Required for widget packages on systems where it
is customary for file names to include an extension that symbolizes the
media type.
Authoring guideline: If it is
anticipated that the widget will be distributed by non-HTTP means, then
include the widget file extension. The widget file extension is not
necessary if the widget package is labeled as a
application/widget when served over HTTP.
7 Configuration
Document
A configuration document is an
[XML] document that has a widget element at its root that is
in the widget namespace. A widget package
must have exactly one configuration document, which
must be located at the root of the widget package.
A valid configuration
document file name is the string config.xml, to be
treated as case-sensitive.
Within a widget package, a configuration document must have a valid configuration
document file name.
User agents must treat files in an arbitrary folder or locale folders that use
the file name config.xml as an arbitrary file.
Authoring guideline: Be sure to
always include a configuration document at the root of the widget package and that
the config.xml file name is in lowercase form.
The following is an an example of a configuration document:
<?xml version="1.0" encoding="UTF-8"?>
<widget xmlns = "http://www.w3.org/ns/widgets"
id = "http://example.org/exampleWidget"
version = "2.0 Beta"
height = "200"
width = "200"
viewmodes = "application fullscreen">
<name short="Example 2.0">
The example Widget!
</name>
<feature name="http://example.com/camera">
<param name="autofocus" value="true"/>
</feature>
<preference name ="apikey"
value ="ea31ad3a23fd2f"
readonly ="true" />
<description>
A sample widget to demonstrate some of the possibilities.
</description>
<author href="http://foo-bar.example.org/"
email="foo-bar@example.org">Foo Bar Corp</author>
<icon src="icons/example.png"/>
<icon src="icons/boo.png"/>
<content src="myWidget.html"/>
<license>
Example license (based on MIT License)
Copyright (c) 2008 The Foo Bar Corp.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
INSULT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
</license>
</widget>
Note: Implementers are
encouraged to expose relevant information provided by the configuration
document to the user. Having "visual metadata" encourages authors to make
full use of the configuration document format. See Step
6 for instructions on how to process a configuration document.
7.1 Namespace
The widget namespace URI for a configuration document is
http://www.w3.org/ns/widgets [XMLNS].
Authoring requirements: Be sure to
declare the widget namespace as part of the widget element. If the namespace
is absent, then Zip archive will be treated as an invalid Zip archive.
7.2
Proprietary Extensions
Implementers intending to extend the configuration document format with
their own [XML] elements and attributes (or those
defined in other specifications) must do so by using a
separate [XMLNS] namespace. This specification does
not define a model for processing [XML] elements
outside the widget namespace.
Example of extending the configuration document format:
<widget xmlns="http://www.w3.org/ns/widgets"
xmlns:ex="http://example.org/">
<icon src="idle.png" ex:role="inactive"/>
<icon src="big.png" ex:role="big"/>
<ex:datasource>{a:"b",c:"d"}</ex:datasource>
<content src="widget.html"/>
</widget>
7.3
Attribute Types
This section defines the different attribute
types used in the configuration document and what constitutes valid
values for those attribute types. Some general rule for how attributes are
to be processed by a user agent or conformance checker are also given in
this section.
User agents should impose their own
implementation-specific limits on the values of otherwise unconstrained
attribute types, e.g. to prevent denial of service attacks, to guard
against running out of memory, or to work around platform-specific
limitations.
An attribute is invalid if its value does not
conform to its said attribute type; that is, if the value of the attribute is in error given the processing rules for that type of
attribute.
- Boolean attribute
-
A boolean attribute is a keyword
attribute that can only be used with a valid boolean value. A valid boolean value is a string that
case-sensitively matches true or false. Unless
specified otherwise, the default behavior, which is used when the
attribute is omitted or has a value other than the two allowed values,
is false. The way a user agent interprets a boolean
attribute is defined as part of an attribute's definition (see, for
example, the feature element's required attribute). The value of this kind
of attribute is retrieved using the rule for getting a
single attribute value.
- Keyword attribute
-
A keyword is a string that is reserved for the purpose of this specification. The
value of a keyword attribute is a keyword that is
one of a finite set specified in the attribute's definition (e.g. the
its:dir attribute defines ltr,
rtl, lro, or rlo as its only
possible values). Authors must use keywords in the case given in this
specification. Implementations must only perform
literal comparisons on the resulting value, and must
not use case-insensitive comparisons. How the value of this
attribute is retrieved depends on the context in which is it used, so
the rule for how to retrieve the value is given when this attribute type
is used.
- Keyword list attribute
-
An attribute defined as taking one or more keywords as a value, which are separated by space characters. The value of this kind
of attribute is retrieved using the rule for getting a
list of keywords from an attribute.
- Media type attribute
-
An attribute whose value is defined as containing a valid media type.
A valid media type is string that
matches the production for valid-MIME-type in the following
[ABNF]:
valid-MIME-type = type "/" subtype *(";" parameter)
The type, subtype, and parameter
tokens are defined in the [MIME] specification. The
value of this kind of attribute is retrieved using the rule for getting a
single attribute value.
- Numeric attribute
-
The value of a numeric attribute is a string containing a valid
non-negative integer. A valid
non-negative integer is a string that consists of one or more code
points in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). For
example, the characters "002", "323", "23214", and so on. The value of
this kind of attribute is retrieved using the rule for getting a
single attribute value.
- Path attribute
-
An attribute defined as containing a valid path. A valid path is one that matches the production of a
zip-rel-path or a zip-abs-path. A Zip absolute path is one that
case-insensitively matches the production of zip-abs-path in the following [ABNF]:
zip-abs-path = "/" zip-rel-path
Note: A zip-abs-path is invalid in the file
name field of a file entry.
The value of this kind of attribute is retrieved using the rule for getting a
single attribute value.
- URI attribute
-
An attribute defined as containing a valid URI. A valid URI is one that matches the URI token of the [URI]
specification or the IRI token of the [RFC3987] specification. The value of this kind of
attribute is retrieved using the rule for getting a
single attribute value.
- Version attribute
-
The value of a version attribute is an arbitrary string (possibly
empty). This specification does not mandate any specific format,
semantics, or special processing rule for the format of this attribute
type. In other words, all strings are valid for this attribute type
within the constraints of [XML] attributes. The value
of this kind of attribute is retrieved using the rule for getting a
single attribute value.
-
Author Guidelines: For the purpose of this
specification, the structure of version tags has no semantics; they are
just treated as arbitrary strings (e.g. '1.0' is not greater than '2.0',
but is simply different). However, for the sake of consistency, one can
choose to use the following [ABNF]:
rec-version-tag = 1*DIGIT ["." 1*DIGIT [ "." 1*DIGIT]
[ ALPHA / SP / DIGIT] ]
- Example valid version tags:
Version 1.0 Beta, 1.0 RC1,
1.0-Build/1580, Joey the dog [5.1.2100].- Example of recommended version tags:
1.0, 1.10.1 beta1, 1.02.12
rc1.
7.4 Other
Attributes
This section describes the behavior and expected usage of other
attributes that are supported either by default as part of the [XML] specification (as is the case with xml:lang) or if the user agent implements the
optional [ITS] specification.
xml:lang attribute-
A keyword attribute defined as
containing a language tag. The [XML] specification defines the xml:lang attribute and its influence on the
contents and attribute values of child elements. The value of this kind
of attribute is retrieved in accordance with the XML.
-
Authoring guideline: Avoid subtags from the IANA
Language Subtag Registry marked as deprecated, grandfathered, or
redundant. The intended purpose of the xml:lang attribute is to declare the primary
language of an element, its attributes, and its descendent nodes.
its:dir attribute-
A keyword attribute defined as
containing a valid its:dir
value (i.e., ltr, rtl, lro,
or rlo). To use the its:dir attribute, the
its namespace (see [ITS]) must be declared on the
element where it is used or somewhere in the element's ancestor chain.
It is optional for authors to use this attribute.
The widget
element serves as a container for the other elements.
- Context in which this element must be used:
- This is the root element of a configuration document.
- Occurrences:
- Exactly one, and must be the root element of the
[XML] document.
- Expected children (in any order):
name: zero or
more (one element is
allowed per language).description: zero or more (one element is allowed per
language).author:
zero or one.license:
zero or more (one element
is allowed per language).icon: zero or
more (elements are grouped by
language).content:
zero or one.feature:
zero or more.preference: zero or more.- Localizable:
- No.
7.5.1
Attributes
id
- A valid URI that denotes an identifier for
the widget. It is optional for authors to use this
attribute.
version- A version attribute that specifies
the version of the widget. It is optional for authors
to use this attribute.
height- A numeric attribute greater than
0 that indicates
the preferred viewport height of the custom start file in CSS
pixels [CSS21]. This value is only applicable to
particular view modes (e.g.,
floating and application mode), meaning that
for certain view modes this
value is ignored. The view
modes that honor the value of this attribute are defined in the [Widgets-Views] specification. It is optional for authors to use this attribute.
width- A numeric attribute greater than
0 that indicates
the preferred viewport width of the instantiated
custom start file in CSS
pixels [CSS21]. This value is only applicable to
particular view modes (e.g.,
floating and application mode), meaning that
for certain view modes this value is ignored. The view modes that honor the
value of this attribute are defined in the [Widgets-Views] specification. It is optional for authors to use this attribute.
xml:langxml:lang attribute. It is optional for authors to use this attribute.viewmodes- A keyword list attribute that
denotes the view modes supported the widget. The value SHOULD be one or more of the following valid view modes as defined
in the [Widgets-Views] specification:
application, floating, fullscreen,
or mini. In addition, the all keyword can be
used to denote that all the valid view mode are supported by the widget.
The default value, which is used when the attribute is omitted or has a
value other than one of the valid view
modes, is floating. The first item represents the
author's preferred view mode, followed by the next most preferred view
mode and so forth. It is optional for authors to use
this attribute.
-
Viewport and view mode are defined in the [Widgets-Views] specification.
7.5.2
Usage Example
The following example shows how the widget element can be used.
<widget xmlns="http://www.w3.org/ns/widgets"
id="http://example.org/exampleWidget"
version="2.0 Beta"
height="200"
width="200"
viewmodes="floating application">
<description>
An example of the possibilities.
</description>
</widget>
7.6 The
name Element
The name element
represents the full human-readable name for a widget
that can be used, for example, in an application menu or in other
contexts.
- Context in which this element may be used:
- In a
widget
element.
- Content model:
- Any.
- Occurrences:
- Zero or more (one
element is allowed per language).
- Localizable via
xml:lang:
- Yes, but the value of the
xml:lang
attribute must be unique for any subsequent element
of this type.
7.6.1
Attributes
xml:langxml:lang attribute. It is optional for authors to use this attribute.its:dir- A valid
its:dir value.
It is optional for authors to use this attribute.
- short
- A string that represents the short name for a widget. Ideally, the
value should be shorter in length than the contents
of the
name
element. Otherwise, the short attribute should not be used. It is optional
for authors to use this attribute.
7.6.2
Usage Example
The following example shows the usage of the name element.
<widget xmlns="http://www.w3.org/ns/widgets">
<name short="Weather">
The Ultimate Weather Widget
</name>
<name short="Boletim" xml:lang="pt">
Boletim Metereológico
</name>
</widget>
7.7
The description Element
The description element represents a
human-readable description of the widget.
- Context in which this element may be used:
- In a
widget
element.
- Content model:
- Any.
- Occurrences:
- Zero or more (one
element is allowed per language).
- Localizable via
xml:lang:
- Yes, but the value of the
xml:lang
attribute must be unique for any subsequent element
of this type.
-
7.7.1
Attributes
xml:langxml:lang attribute. It is optional for authors to use this attribute.its:dir- A valid
its:dir value.
It is optional for authors to use this attribute.
7.7.2
Usage Example
An example usage of the description element.
<widget xmlns="http://www.w3.org/ns/widgets">
<name>Tornado Chaser</name>
<description>
Combining the latest weather info with your GPS position,
this widget alerts you of any significant storm activity in your
area. When a big one hits, the widget plots the best route on a map based
on the storm's trajectory so you can chase it! With support for
built-in cameras, you can quickly upload all the meteorological action to
your blog or to the insane storm chaser web site! Awesome!
</description>
</widget>
7.8 The
author Element
An author element represents people
or an organization attributed with the creation of the widget.
- Context in which this element may be used:
- As a child of the
widget element.
- Content model:
- Any.
- Occurrences:
- Zero or one.
- Localizable via
xml:lang:
- No. Only the first instance of this element in document order
will be used, regardless of the value of
xml:lang (if any).
7.8.1
Attributes
href- A URI attribute that represents a link
that is associated with the author (e.g. the homepage of the author). It
is optional for authors to use this attribute.
email- A string that represents an email address associated with the author.
It is optional for authors to use this attribute.
-
xml:langxml:lang attribute. It is optional for authors to use this attribute.its:dir- A valid
its:dir value.
It is optional for authors to use this attribute.
7.8.2
Usage Example
The following example shows the expected usage of the author element.
<widget xmlns="http://www.w3.org/ns/widgets">
<name>Cup-a-Joe's Cafe Finder Widget</name>
<author href = "http://dahut.example.org"
email = "joe@example.org">
Joey and Princesa Bacalhau
</author>
</widget>
7.9
The license Element
The license
element represents a software license,
which includes, for example, a usage agreement, redistribution statement,
and/or a copyright license terms under which the content of the widget
package is provided.
- Context in which this element may be used:
- As a child of the
widget element.
- Content model:
- Any.
- Occurrences:
- Zero or more (one
element is allowed per language).
- Localizable via
xml:lang:
- Yes, but the value of the
xml:lang
attribute must be unique for any subsequent element
of this type.
Authoring Guideline: Localized
license shouldn't be used to present different versions of a license, just
translations of the same license.
7.9.1
Attributes
href- A valid URI or a valid
path that points to a representation of a software and/or content
license. When the
href attribute is used, the user agent should provide users the ability to view or otherwise
link to the referenced license.
- If the href attribute contains a valid path
to a file within the widget package, then the user agent should use the rule for identifying
the media type of a file to identify the media
type of the file being referenced. It is optional
for authors to use this attribute.
xml:langxml:lang attribute. It is optional for authors to use this attribute.its:dir- A valid
its:dir value.
It is optional for authors to use this attribute.
7.9.2
Usage Example
This example shows the expected usage of the license element's
href attribute.
<widget xmlns="http://www.w3.org/ns/widgets">
<license href="http://creativecommons.org/licenses/by/3.0/">
Creative Commons Attribution License
</license>
</widget>
This example shows the expected usage of the license element when the
href attribute is omitted.
<widget xmlns="http://www.w3.org/ns/widgets">
<license>
Copyright (c) 2008 The Foo-Bar Corporation
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN THE SOFTWARE.
</license>
</widget>
7.10 The
icon Element
The icon element
represents a custom icon for the widget. A user
agent should expose a custom
icon in a way that it is visible to the end user.
- Context in which this element may be used:
- As a child of the
widget element.
- Content model:
- Empty.
- Occurrences:
- Zero or more (elements are
grouped by language).
- Localizable via
xml:lang:
- No. Relies on folder-based
localization.
7.10.1
Attributes
src- Required. A path attribute that points to a file inside the widget package. It is required for authors to use this attribute.
width- A numeric attribute greater than
0 that
represents the width of the icon in CSS
pixels [CSS21]. This attribute is only
applicable to graphic formats that have no intrinsic width or height
(e.g., SVG). If the file pointed to by the src attribute is a supported raster graphic, then
the user agent will ignore this value. If the file pointed to by the src attribute is of a vector graphic format, then
this value must be used. It is optional for authors to use this attribute.
height- A numeric attribute greater than
0 that represents the height of the icon in CSS
pixels [CSS21].This attribute is only applicable
to graphic formats that have no intrinsic width or height (e.g., SVG). If
the file pointed to by the src attribute is a supported raster graphic, then
the user agent will ignore this value. If the file
pointed to by the src
attribute is a vector graphic format, then this value must be used. It is optional for
authors to use this attribute.
Authoring guideline: Refrain from
using the width and height attributes for raster
graphic formats, as the widget user agent
will ignore these values.
7.10.2
Usage Example
This example shows the expected usage of the icon element. The example declares
three icon elements, two of which are raster and one of which is an [SVGTiny] file. The raster graphics would be used for
display contexts smaller than 256x256 pixels. Document order of
the elements is irrelevant.
<widget xmlns="http://www.w3.org/ns/widgets">
<icon src="icons/medium.png"/>
<icon src="icons/big.svg" width="256" height="256"/>
<icon src="icons/tiny.png"/>
</widget>
7.11
The content Element
The content
element is used by an author to declare which custom start file the user agent will use
when it instantiates the widget.
- Context in which this element may be used:
- As a child of the
widget element.
- Content model:
- Empty.
- Occurrences:
- Zero or one.
- Localizable via
xml:lang:
- No. Relies on folder-based
localization.
7.11.1
Attributes
src- A path attribute that allows an author
to point to a file within the widget package. It is required for authors to use this attribute.
type- A media type attribute that
indicates the media type of the file
referenced by the
src attribute. When
the value is absent, the user agent will assume the value
text/html. It is optional for authors to
use this attribute.
encoding- A keyword attribute that denotes the character encoding of the file
identified by the
src attribute. The
allowed value is the "name" or "alias" of any
"Character Set" listed in [IANA-Charsets]. A user agent MUST support [UTF-8], which has the
"UTF-8" name in [IANA-Charsets]; all other character encodings
are optional.
- It is optional for authors to use this attribute.
-
When the value of encoding is absent
or in error, the user agent will assume the default encoding which is the value UTF-8.
Authoring Guideline: Where aliases
are given by the [IANA-Charsets], authors are
encouraged to use those aliases marked as "preferred MIME name".
-
-
7.11.2
Usage Example
This example shows the expected usage of the content element:
<widget xmlns="http://www.w3.org/ns/widgets">
<content src="myWidget.html"/>
</widget>
This example shows the content element being used with a
encoding attribute to override the default value of this
attribute (UTF-8) with the GB2312
character set, which the author has used to encode simplified Chinese
characters:
<widget xmlns="http://www.w3.org/ns/widgets">
<name xml:lang="zh-cn">古老瓷地图</name>
<name>Ancient Chinese Maps</name>
<content src="china-maps.html" encoding="GB2312"/>
</widget>
This example shows the content element being used with a type attribute to
instantiate a widget created with a proprietary media type:
<widget xmlns="http://www.w3.org/ns/widgets">
<name>Location-Based Games Finder</name>
<content src="lbg-maps.swf" type="application/x-shockwave-flash"/>
<feature name="http://example.org/api.geolocation"
required="false"/>
</widget>
7.12
The feature Element
A feature is a runtime component (e.g. an
Application Programming Interface or video decoder) that is not part of
the specified set provided by the Widgets 1.0 family of
specifications. The feature element serves as a standardized means
to request the binding of an (URI) identifiable runtime component to a
widget for use at runtim