Open File Formats Technology Working Group (OFF.TWG)

Name: Open File Formats Technology Working Group (OFF.TWG)
Identifier: OFF.TWG
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Chairs: Nagel, Nicholas H. (Grid Institute and Boston College), Walsh, Aaron E. (Grid Institute and Boston College)
Liaisons: Beaubois, Terry A. (Montana State University and liaison to the National Institute of Building Sciences buildingSMART Alliance)


The Open File Formats Technology Working Group (OFF.TWG) is responsible for defining, evolving and maintaining open, platform-neutral file formats that enable learning objects and experiences to be seamlessly deployed across Immersive Education technology platforms.



This TWG is open to all members of the Immersive Education Initiative having:

  1. experience designing or developing file formats for virtual worlds, simulators or video games, or
  2. experience translating or transforming file formats, or
  3. experience developing file format tools, or
  4. experience developing content authoring tools, or
  5. extensive experience developing virtual worlds, simulators or video games.

TO JOIN: Please complete this form to join this TWG.



"Create Once, Experience Everywhere"

In the context of Immersive Education the term platform refers to any virtual world, simulator or 3D game-based environment that may be used for teaching or training purposes. The Immersive Education platform has evolved considerably over the past decade and the 3rd generation ("next generation") is now under development. Whereas the previous two generations of Immersive Education were based on specific client-side platforms tied to proprietary server-side infrastructures, the future of Immersive Education revolves around multiple client-side platforms working in unison through the server-side Education Grid.

Based upon open source technologies and open standards, the Platform Ecosystem and Education Grid will provide educators with a comprehensive end-to-end infrastructure for a new generation of virtual world learning environments, interactive learning games, and simulations. To this end the Immersive Education Initiative has a mandate to design, develop and promote open and platform-neutral file formats that enable interoperable learning objects and experiences to be seamlessly deployed across a wide variety of virtual world and game platforms (e.g., Second Life, Croquet/Cobalt, Wonderland, and other 3D/VR platforms) as Figure 1 illustrates.

Education Grid. CLICK FOR FULL SIZE...

Figure 1 [click image for full size]: Open, platform-neutral file formats will make it possible for learning objects and experiences to be seamlessly deployed across a wide variety of virtual world and game platforms.

In this figure the Education Grid, depicted by the inner gray circle, is shown delivering learning content to Second Life, Wonderland, Croquet/Cobalt and other Immersive Education platforms (the purple sphere represents both individual learning objects and complete learning experiences). In other words, each Immersive Education platform will support the same open file format in the near future.

Second Life, Wonderland, and Croquet/Cobalt do not currently support the same 3D/VR file formats, however. Today's virtual world and game platforms are essentially walled gardens; users are not able to interact with the same objects or experiences from different platforms, nor are users of one platform able to interact with users residing in another platform. Although the Immersive Education Initiative does not plan to address the latter concern (user interoperability across platforms), through the Open File Formats Technology Working Group we are actively standardizing cross-platform content interchange by adopting and promoting open, platform neutral 3D/VR file formats that enable the promise of "create once, experience everywhere."

Native File Formats vs. Transcoding vs. Direct Support for Open File Formats

Today's Immersive Education technology platforms do not support the same 3D/VR file formats. Each platform currently supports its own native file format(s). Second Life, for example, supports a proprietary format developed by Linden Labs that is based on "prims". Wonderland, in contrast, currently supports the mesh-based Extensible 3D format (X3D, an international ISO/IEC standard) and as of version 0.5 will support COLLADA. Croquet/Cobalt, meanwhile, supports the mesh-based ASE (ASCII Scene Export) format and it previously supported the OBJ format (OBJ support is broken in the current version of Croquet/Colbalt).

Consequently, there is no way for these platforms to exchange 3D/VR content or to provide users with the same immersive learning experience. Because each platform supports different native file formats end users are limited in terms of the learning objects and learning experiences that are available to them from within a given platform. Content authors must either re-create content for each platform or (more commonly) create content for only platform and simply ignore the others as Figure 2 illustrates:

Native File Formats. CLICK FOR FULL SIZE...

Figure 2 [click image for full size]: Today's virtual world, simulator and game platforms do not support the same 3D/VR file formats. Each platform instead supports its own native file format(s). Because of the cost, time, and complexity involved with building content for multiple platforms the vast majority of content authors focus on only one platform and ignore all others. In the rare case where the same object or learning experience is created for multiple platforms the end result is typically redundant and imperfect owing to differences between file formats and platform rendering engines.

Transcoding tools, as Figure 3 illustrates, can eliminate much of the effort associated with making the same object or experience available to multiple platforms. Transcoding is a suboptimal stop-gap measure, however, that frequently requires manual "touch-up" work and re-coding of scripts. In contrast, platforms can directly support open file formats and skip the transcoding process altogether (see Figure 4).

Transcoding Process. CLICK FOR FULL SIZE...

Figure 3 [click image for full size]: Transcoding tools can automate the process required to make 3D/VR content available to multiple platforms. In this figure an object or experience (depicted by the purple file) is transcoded into multiple native formats, one for each platform. Although transcoding can automate much of the work associated with making content available to multiple platforms, the process isn't perfect. Because of file format differences some manual refinement is usually necessary. Scripts, in particular, may need to be manually re-coded for each platform.

Direct support (transcoding step is no longer necessary). CLICK FOR FULL SIZE...

Figure 4 [click image for full size]: Platforms that directly support open file formats can skip the transcoding process entirely. Direct support is preferable to transcoding for three major reasons: 1) transcoding is an imperfect process that often produces suboptimal results that require subsequent "hand tuning" by an experienced content author, 2) scripts are difficult to transcode and may need to be manually re-coded from scratch for each platform by an experienced programmer, and 3) transcoding is an inconvenient extra step that takes time and effort.

Transcoding vs. Direct Support

Transcoding is a stop-gap measure that is only necessary when a platform doesn't directly support the target file format. Direct support is preferable to transcoding for three major reasons. First, and foremost, is the fact that transcoding is rarely a perfect process that often produces suboptimal results that require subsequent "hand tuning" by an experienced content author. In addition, because scripts can't easily be transcoded they may need to be re-coded for each platform by an experienced programmer. Finally, transcoding is an inconvenient extra step that can be skipped by platforms that directly support the target format.

Although direct support is preferred, transcoding is a reasonable approach when a platform already has a complete, well-defined exchange format that fully represents every feature of the platform. In such cases a transcoder tool can be written to convert from that format to another format. A disadvantage of this approach is that a custom transcoder tool needs to be written for each platform in order for that platform's file format(s) to be converted into the format(s) supported by other platforms. For example, transcoding services to support the current Immersive Education virtual worlds platforms will require the development of six custom transcoder tools (assuming a total of three platforms, namely Second Life, Wonderland and Croquet/Cobalt). As more formats and platforms are introduced the number of transcoder tools required increases exponentially, which in turn makes maintenance and support difficult if not entirely unfeasible [if N is the number of platforms, N*(N-1) transcoders are required assuming one-way transcoders].

Transcoding to and from an intermediate format reduces this concern; for each platform only two transcoder tools are required (one each to convert to and from the intermediate format). This approach is much more manageable and cost effective. The intermediate format used must be complete or extensible enough to represent all of the features required by each platform, however, so that no data will be lost during the transcoding process.

Another option is to add a plug-in or other code to a platform to directly import and export to an intermediate format. This is the best approach in terms of the platform's users, since a user can export the file once and then import it directly into other programs without being required to run a transcoder every time. In most cases, writing this kind of direct import/export plug-in is easier than developing a stand-alone transcoder. If a platform doesn't already have its own interchange format using one can avoid the need to design a new format and the tools that use it. This is also a good solution in cases where a platform vendor wishes to keep their native file formats confidential.

Compatibility and Conformance Testing

Conformance suites are necessary to provide developers with adequate testing materials during the implementation of transcoding tools or when enhancing a platform to directly support a target file format. Conformance test suites are intended to be used as a tool to aid developers during the implementation of transcoding tools and direct support for a specific open file format described in this document. For example, a COLLADA conformance test suite is necessary for developers to build COLLADA transcoding tools or to implement direct support for the COLLADA file format for a given platform.

  • Conformance test suites will be developed as collections of open and freely available materials that any individual or organization can utilize.

  • Conformance test suites will include content (avatars, objects, models and environments) and test programs (code) that measure the quality and validity of the import/ export capabilities of a transcoding tool or platform. Exported files, for example, will be passed through a XML validation process that will test the exported content for conformance with the target file format specification.

  • Test suites will be comprised of avatars, objects, models and environments taken from a variety of existing content repositories and will also include newly constructed materials that are created from ongoing Immersive Education content development efforts.

  • · Platform and tool certification is outside the scope of this project; conformance test suites will be provided as informational resources only.



The objectives of the Open File Formats Technology Group are:

  1. To define, evolve and maintain open, platform-neutral file format standards for representing educational content in Immersive Education platforms and environments, and
  2. To facilitate the use of those standards by participating in the development of specifications, conformance suites, technologies and reference applications based on these standards.



  1. The adoption of an existing open file format standard, or set of standards, that will enable Immersive Education platforms to support comprehensive interactive learning environments that can be readily deployed over the Internet, or
  2. The design and development of new file format standards that meet the above requirements, and
  3. The adaptation and/or development of Immersive Education platforms to support the open file formats and content conformance suites produced by this Technology Working Group, and
  4. Zero-loss interchange of core features of conformant learning environments between Immersive Education platforms.



This Technology Working Group is closely related to:

  • Accessibility Technology Working Group (ACC.TWG)
  • Assessment, Evaluation and Grading Technology Working Group (AEG.TWG)
  • Education Grid Technology Working Group (EDG.TWG)
  • Metadata and Taxonomy Technology Working Group (MTX.TWG)
  • Metrics Technology Working Group (MET.TWG)
  • Open Worlds Technology Working Group (OPW.TWG)
  • Tagging, Rating and Review Technology Working Group (TRR.TWG)



Open File Format Use Case: Deploy Content to Multiple Platforms

Develop educational content that can be used across multiple Immersive Education environments.


  1. A team of researchers and content developers at the "Center for the Study of Population and Urban Development" creates a simulation of a city and surrounding farmland which allows end-users to manipulate parameters and observe the effects on issues related to logistics and supply lines infrastructure. Participating in the simulation engenders better understanding of micro and macro economics, logistics, demographics and population trends. The creators want to make their content available as part of a creative commons and enable widespread distribution of the simulation.

  2. For their senior project, a group of middle school students develop a model of the Greek Acropolis designed to scale. In developing the model, the students arrive at enhanced understanding of basic principles of geometry, architecture, measurement and materials. The students want to add their model to a virtual world which currently has a "stub" (i.e., designated spot lacking a detailed version) in place of the model edifice.

Use Case Diagram

Use Case Diagram: Developing educational content that can be used across multiple Immersive Education environments.


From this use case we can identify a number of roles and actions that must be supported by open file formats defining content for Immersive Education.

  1. Content developers (creators) create content which can be applied toward training and education.
  2. Content developers add content to repository and make available for distribution.
  3. Educators obtain content and deploy to platform of choice. Given a common file format, Educators can deploy content to any of a number of platforms that support that format. No single individual or organization can develop and maintain educational content to meet all curricular needs. However, given a common file format, educators, researchers, and content developers can collaborate to develop content that can be used across all participating platforms.
  4. Learners access content and interact with it accordingly.

Note: A real world individual might take on any or all of these roles at one time or another. As such, the roles suggested here are considered to be defined against the system rather than as embodying real world job titles or responsibilities. Anyone with the prerequisite knowledge and skills can develop content in any given domain. The critical point is that content can become accessible across all participating platforms.

Open File Format Use Case: "Walk Between Worlds"

Traverse multiple Immersive Education environments, using multiple Immersive Education platforms, with a singular avatar. In other words, "walk between worlds".


  1. An educator identifies two or more simulations she'd like to use in her class. However, the simulations happen to be deployed to distinct servers using distinct Immersive Education platforms. The educator's class requires that learners can traverse the distinct environments with a singular avatar (i.e., one virtual representation of the learner composed of one model, an associated set of scripted behaviors, assets, metadata, etc.).

Use Case Diagram

Use Case Diagram: Traversing worlds with a singular Avatar.

Open File Format Use Case: Tagging Content with Metadata

Tagging content with metadata tags (keyword descriptors) to facilitate text-based search and retrieval.


  1. The team of developers for a economic simulator wish to “tag” the content files they have created with appropriate keywords and descriptions to facilitate text-based retrieval of their content from Education Grid repositories and from the Web using search engines (such as Google, Yahoo, etc.). The developers therefore embed the tag "economics simulation" directly inside of the content file(s) that comprise their learning simulation.

    In contrast, an educator using the economic simulation decides to apply the tags "logistics" and "supply-line management" to the content. Because the educator is not an author of the content the metadata she provides is associated with, but not imbedded inside of, the content files that make up this learning experience.

    Students using the economic simulator further tag it with metadata they provide, resulting in three different levels of metadata associated with this content: 1) author tags, 2) educator tags, and 3) student tags.

Open File Format Use Case: Automated Assessment of Student Performance

Automated and computer-based assessment of students using Immersive Education environments.


  1. On Friday a K-12 teacher assigns a quest-based virtual world as homework for her middle school students. Over the weekend students are required to explore virtual Egypt and gather ancient artifacts hidden throughout the tombs and pyramids. To obtain all of the artifacts students must explore the virtual environment and use the skills and historical knowledge that they acquire in order to advance in their quest.

    Over the weekend the teacher users her Web browser to view a text report that tracks student progress. The text-based report is generated automatically by the learning environment, and indicates how long each student has engaged in the quest, the items they have found, how long (and to what extent) they interact with and examine the objects they’ve found, and so forth. All of this data is provided in text format, along with a summary letter grade that is assigned to each student based on their overall progress.

    On Monday the teacher meets her students in virtual Egypt and sees, visually, the progress of her students. Students that have successfully completed the quest are fully clothed in royal Egyptian garments and are wearing ornate jewelry and special items from that period (such as scarab necklaces, gold head bands, etc.). Students that have begun but not yet completed the quest have less impressive Egyptian outfits, and lack the fancy jewelry worn by the higher-scoring students. Students who have not completed any part of the quest are wearing plain modern-day street clothing, such as jeans and t-shirts.

    All clothing and jewelry is automatically attached to the students during their quest in direct relation to the work they’ve done, which in turn provides an immediate visual indication of their progress in addition to a reasonable degree of virtual peer pressure: students can see how they compare to their fellow classmates merely by the appearance of their own avatar.



Note: Not all materials listed under this section are open and freely available. Some are proprietary technologies that either build upon or utilize open standards or technologies or have proprietary features and/or capabilities that are useful for comparison with open alternatives.

  • COLLADA community:

  • COLLADA standard:

  • Developing Web Applications with COLLADA and X3D (white paper):

  • ECMA-363 (aka U3D; Universal 3D):

  • ECMA International:

  • Extensible 3D (X3D):

  • FBX:

  • jMonkey Engine (jME):

  • Khronos Group:

  • MPEG-4:

  • Object-Oriented Graphics Rendering Engine (OGRE):

  • OpenSceneGraph:

  • Virtual Reality Modeling Language (VRML):

  • Web3D Consortium:



  1. Open File Formats Project Overview [Working Draft Planning Document; PDF rendition]. Immersive Education Initiative et al. May 13, 2008.

  2. OFF.TWG 3D and Virtual Reality (3D/VR) File Format Requirements [Public Working Draft; HTML rendition]. Immersive Education Initiative et al.

  3. High resolution avatars, objects, and environments. Immersive Education Initiative. May 9, 2008.

  4. Immersive Education content review, ranking, tagging, vetting. Immersive Education Initiative. March 21, 2008.

  5. Avatar tracking and analysis meeting, demonstrations, discussion. Immersive Education Initiative. March 14, 2008.

  6. Platform Ecosystem and Education Grid status and review. Immersive Education Initiative. April 18, 2008.

  7. The Education Grid:

  8. Education Grid Requirements Specification [Working Draft]. Immersive Education Initiative.

  9. Immersive Education Initiative Launches The Education Grid. Immersive Education Initiative. June 20, 2008.

  10. Immersive Education Initiative announces Education Grid and Platform Ecosystem at Boston Summit. Immersive Education Initiative. January 22, 2008.



Technology Working Group telephone conferences and/or virtual world meetings are held once a month, with additional telephone conferences and virtual world meetings arranged at the discretion of the group.

Face-to-face (f2f) meetings are one- to three-day sessions held approximately twice a year, with additional f2f meetings arranged at the discretion of the group. To maximize working relationships between the Technology Working Group and relevant standards bodies and vendor organizations f2f meetings may be held in conjunction with industry events, standards meetings, or on location at member or collaborator organizations. All f2f meetings are announced through the group's email list and Web page.

Refer to the Immersive Education Initiative Process Document for details



The proceedings of this Technology Working Group are confidential and restricted to members of this group. As an open standards organization, and in recognition of the need for ongoing accountability to the general public, will periodically publish a public summary of all technical decisions (together with the rationales for these decisions) made by this group since the last public summary. Deliverables produced by this group, such as specifications and software implementations, will be provided to invited experts and collaborators for review prior to being furnished to the general public.

Refer to the Media Grid Intellectual Property Policy for details


Document revised 2008-10-21