(registered 2013-10-30, last updated 2013-10-30)
Name : Leonard Daly & Don Brutzman
Email : x3d-chair&web3d.org
MIME media type name : Model
MIME subtype name : Standards Tree - x3d+xml
Required parameters : None
Optional parameters :
None
Encoding considerations : binary
Security considerations :
A number of relevant references pertain to X3D model security, particularly
RFC 4288, Media Type Specifications and Registration Procedures (Security
Requirements) [http://tools.ietf.org/html/rfc4288#section-4.6].
* Complex media types: There are no X3D directives that access local resources
except those related to the graphical display of content and the necessary
system resources to make that happen. The X3D specification does allow for
scripts to execute a variety of actions including changing the URL and accessing
local resources. Any implementations that execute scripts MUST give
consideration to their application's threat models and those of the individual
features they implement; in particular, they MUST ensure that untrusted content
is not executed in an unprotected environment.
* Active content: We are interpreting active content to mean any and all content
that is not static and unchanging while the designated URL is displayed. The
intent of X3D is to provide active content to the user. This requires system
resources in the form of memory, CPU processing, and graphics processing. Users
of X3D desire active and are aware of the system demands.
* Release of information: The X3D specification does not require any information
be sent from the user's computer. A particular implementation may request
information and distribute it. It is up to the implementer and user to negotiate
the terms of service for that particular application.
* Decompression issues: Several activities can occur when loading an X3D scene
that have security implications.
- X3D files can embed url links for loading other resources such as images,
scripts, movies, audio files and other X3D scenes
- Embedded or linked scripts can be in Javascript, Java or (optionally) other
languages
- Compressed binary scenes can contain two types of decompression:
information-based (.gzip, Fast Infoset) and geometric-based (produces polygonal
structures) which can be computationally expensive
- Recursive techniques are not typically allowed in 3D scene constructs
- Regular user-agent precautions used by Web browsers for HTML content should
also apply
* External security considerations: There is nothing in the X3D specification
that requires or prevents security assurances. A particular implementation may
request information and distribute it. It is up to the implementer and user to
negotiate the terms of service for that particular application.
Scripting is defined as being available for the specification. Two scripting
languages are defined: ECMAScript and Java. Each scripting language is
controlled by its local security model. As the content may run in many different
situations, the X3D specification does not impose specific security policies.
For example, some standalone applications will want to directly interact with
the local file system, network or database, while others that run in a web
browser would use the web-browser's security model.
X3D Graphics scenes can utilize the World Wide Web Consortium (W3C) Security
Recommendations [http://www.w3.org/Security/] for XML Signature
[http://www.w3.org/TR/xmldsig-core/] and XML Encryption
[http://www.w3.org/TR/xmlenc-core/], in either the .x3d (plain text) and .x3db
(compressed binary) encodings.
* Basic examples demonstrating use of the current W3C Recommendations for XML
Signature and XML Encryption are maintained online at
- http://www.web3d.org/x3d/content/examples/Basic/Security
- http://www.web3d.org/x3d/content/examples/Basic/Security/X3dSecurityReadMe.html
X3D security considerations are a close match to HTML. JavaScript or Java
scripts may be linked internal to an X3D scene, or external to an X3D scene by
an encapsulating HTML browser. Relevant informational review references follow.
* HTML Mime Type Security Considerations [http://tools.ietf.org/html/rfc2854#section-7]
- Excerpt: In addition, the introduction of scripting languages and interactive
capabilities in HTML 4.0 introduced a number of security risks associated with
the automatic execution of programs written by the sender but interpreted by the
recipient. User agents executing such scripts or programs must be extremely
careful to insure that untrusted software is executed in a protected environment.
* HTML4 Recommendation, B.10 Notes on security [http://www.w3.org/TR/html401/appendix/notes.html#h-B.10]
- Excerpt: Anchors, embedded images, and all other elements that contain URIs as
parameters may cause the URI to be dereferenced in response to user input. In
this case, the security issues of [RFC1738 - http://tools.ietf.org/html/rfc1738],
section 6, should be considered. The widely deployed methods for submitting form
requests -- HTTP and SMTP -- provide little assurance of confidentiality.
Information providers who request sensitive information via forms -- especially
with the INPUT element, type="password" -- should be aware and make their users
aware of the lack of confidentiality.
* HTML5 security references [http://www.w3.org/Security/wiki/HTML5]
- Details regarding specific HTML5 elements seem to be not applicable to X3D mime types
Interoperability considerations :
Published specification :
All revisions of the X3D specification is maintained online at
http://www.web3d.org/realtime-3d/specification/all The most recent specification
is available from the ISO website (for a fee) or from Web3D Consortium (without
charge)
ISO/IEC 19776-1.2:2009 - XML Encoding
http://www.web3d.org/files/specifications/19776-1/V3.3/index.html [per ISO
requirements, this is a frames definition page]
Applications which use this media :
The applications that use (or would use) the media type (model/x3d+xml) are
those that display, create, edit, import, or export 3D model content using the
X3D standard. A short list of the applications include:
* Blender (Open source, runs on Windows, Macintosh, Linux)
* BS Contact (from Bitmanagement, runs on Windows, Macintosh, Linux)
* Flux (from Media Machines, runs on Windows)
* FreeWRL (Open source, runs on Windows, Macintosh, Linux)
* Instant Reality (Fraunhofer, runs on Windows, Macintosh, Linux)
* Octaga VS Player (from Octaga VS, runs on Windows)
* Rawkee (Open source Maya exporter, runs in Maya)
* Vivaty (from Vivaty, runs on Windows, Flash based)
* X3D-Edit and X3D Validator (from Naval Postgraduate School, Java based)
* X3DOM (Open source, runs on Windows, Macintosh, Linux, iPad)
* Xj3D (Open source from Web3D Consortium, Java based)
* See X3D Resources (http://www.web3d.org/x3d/content/examples/X3dResources.html)
for a comprehensive list of supporting applications
Additional information :
1. Magic number(s) : None
2. File extension(s) : x3d
3. Macintosh file type code : Text
4. Object Identifiers: None
The X3D standard is a continuation of the VRML standard that is defined in
RFC2077. As part of this work, several large modifications were made to the file
format and specification. The basic premise for the specification continues the
VRML design rational. The MIME types and file extensions were changed to
indicate this modified standard.
Content Sub-types
Each content type may have an additional Content-Encoding to indicate whether
the content has been compressed using GZIP in addition to the basic textual
encoding. This is also indicated by modifying each file extension with the
character "z". For example, the plain text VRML-encoded file format would use
the extension ".x3dv", and if compressed using GZIP uses the extension ".x3dvz"
Person to contact for further information :
1. Name : X3D Working Group Chairs (Leonard Daly & Don Brutzman)
2. Email : x3d-chair&web3d.org
Intended usage : Common
Author/Change controller : Web3D Consortium Presently we were in a very dark road, and at a point where it dropped suddenly between steep sides we halted in black shadow. A gleam of pale sand, a whisper of deep flowing waters, and a farther glimmer of more sands beyond them challenged our advance. We had come to a "grapevine ferry." The scow was on the other side, the water too shoal for the horses to swim, and the bottom, most likely, quicksand. Out of the blackness of the opposite shore came a soft, high-pitched, quavering, long-drawn, smothered moan of woe, the call of that snivelling little sinner the screech-owl. Ferry murmured to me to answer it and I sent the same faint horror-stricken tremolo back. Again it came to us, from not farther than one might toss his cap, and I followed Ferry down to the water's edge. The grapevine guy swayed at our side, we heard the scow slide from the sands, and in a few moments, moved by two videttes, it touched our shore. Soon we were across, the two videttes riding with us, and beyond a sharp rise, in an old opening made by the swoop of a hurricane, we entered the silent unlighted bivouac of Ferry's scouts. Ferry got down and sat on the earth talking with Quinn, while the sergeants quietly roused the sleepers to horse. Plotinus is driven by this perplexity to reconsider the whole theory of Matter.477 He takes Aristotle¡¯s doctrine as the groundwork of his investigation. According to this, all existence is divided into Matter and Form. What we know of things¡ªin other words, the sum of their differential characteristics¡ªis their Form. Take away this, and the unknowable residuum is their Matter. Again, Matter is the vague indeterminate something out of which particular Forms are developed. The two are related as Possibility to Actuality, as the more generic to the more specific substance through every grade of classification and composition. Thus there are two Matters, the one sensible and the other intelligible. The former constitutes the common substratum of bodies, the other the common element of ideas.478 The general distinction between Matter and Form was originally suggested to Aristotle by Plato¡¯s remarks on the same subject; but he differs325 from his master in two important particulars. Plato, in his Timaeus, seems to identify Matter with space.479 So far, it is a much more positive conception than the ?λη of the Metaphysics. On the other hand, he constantly opposes it to reality as something non-existent; and he at least implies that it is opposed to absolute good as a principle of absolute evil.480 Thus while the Aristotelian world is formed by the development of Power into Actuality, the Platonic world is composed by the union of Being and not-Being, of the Same and the Different, of the One and the Many, of the Limit and the Unlimited, of Good and Evil, in varying proportions with each other. The Lawton woman had heard of an officer's family at Grant, which was in need of a cook, and had gone there. [See larger version] On the 8th of July an extraordinary Privy Council was summoned. All the members, of whatever party, were desired to attend, and many were the speculations as to the object of their meeting. The general notion was that it involved the continuing or the ending of the war. It turned out to be for the announcement of the king's intended marriage. The lady selected was Charlotte, the second sister of the Duke of Mecklenburg-Strelitz. Apart from the narrowness of her education, the young princess had a considerable amount of amiability, good sense, and domestic taste. These she shared with her intended husband, and whilst they made the royal couple always retiring, at the same time they caused them to give, during their lives, a moral air to their court. On the 8th of September Charlotte arrived at St. James's, and that afternoon the marriage took place, the ceremony being performed by the Archbishop of Canterbury. On the 22nd the coronation took place with the greatest splendour. Mother and girls were inconsolable, for each had something that they were sure "Si would like," and would "do him good," but they knew Josiah Klegg, Sr., well enough to understand what was the condition when he had once made up his mind. CHAPTER V. THE YOUNG RECRUITS Si proceeded to deftly construct a litter out of the two guns, with some sticks that he cut with a knife, and bound with pawpaw strips. His voice had sunk very low, almost to sweetness. A soft flurry of pink went over her face, and her eyelids drooped. Then suddenly she braced herself, pulled herself taut, grew combative again, though her voice shook. HoME²Ô¾®Ïè̫ʲôÐÇ×ù
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