Re: XML is text-only ... why?
To be clearer than I was: Stephen D. Williams wrote: > Fast Infoset is not what W3C Efficient XML Interchange (EXI) is based > on, although it is one of the candidates considered in detail, along > with my Efficiency Structured XML 1.0 (ESXML). > > Here is our first public working draft of the EXI format: > http://www.w3.org/TR/2007/WD-exi-20070716/ > > I feel it is an incomplete baseline in a number of ways, however it > includes most of the base structure and encoding method and is a > significant milestone. The key considered candidate turned out to be "Efficient XML" from AgileDelta which, along with contributions from at least one other format (which doesn't seem to be publicly noted at the moment), is the basis for the EXI format specification. I think of this format specification as a baseline that can be improved, but it may be that it is complete enough and further changes aren't worth the complexity or other costs. "AgileDelta's Efficient XML" (EFX) product, and therefore "W3C's Efficient XML Interchange" (EXI) specification, has a clever reformulation of the kinds of ideas used in both older bit-wise encoding formats (MPEG4's hand-optimized, but static, scene description encoding comes to mind, along others) and a number of dynamic encoding methods. This improved reformulation directly addresses the flexibility and architecture of XML while closely taking into account exactly what information is known while encoding and decoding. Additionally, some interesting scalar encoding methods are used when typed values are enabled. I think it can be improved, and should be improved for something that is likely to be used very widely. Already though it leads as a solution to a number of related general problems compared to anything else. Other candidates overlapped in some ways and investigated other aspects of the problem set to a greater degree, which may lead to additional useful capabilities. The first thing to get right is the structure and basic methods; this is what the current specification does. > I initiated the OpenEXI open source implementation and Santiago > Pericas-Geertsen and others quickly joined. OpenEXI is hosted as an > open source project by Sun, although I don't believe the project > codebase is public quite yet. OpenEXI is either a project independent of the W3C EXI working group or only loosely associated with it, depending on how you look at it. The chartered output of the EXI working group is the specification and supporting documents. OpenEXI is an independent open implementation of the specification and of experimental additions to it. There are a number of large and small participant companies and individuals in OpenEXI and much progress has been made. Suggesting it was inevitable by someone in the group and it is separate from the W3C XML Binary Characterization (XBC) and EXI working groups, except for the overlap of participants and the benefit to the work of the group in having an open implementation. We have as a group put in several years of hard work diligently formulating and answering the need for a nearly universal and flexibly efficient representation of mostly arbitrary data that is feature-compatible with XML and competitive with nearly all other solutions. The path is difficult and it is a sign of health that there are differences of opinion in areas we haven't reached complete consensus. It is important to avoid adding endless features which create complexity, code size, and interoperability issues, but at the same time it is just as important to avoid freezing a solution at the first sign of success when additional performance and coverage of additional use cases can be had for incremental work. Another big part of the benefit of the working groups has been a crystallization of related ideas, including use cases, requirements, measurement methodology, and ways of comparing and analyzing different methods and degrees of encoding data. While the documentation may be large enough to be hard to digest, some ideas should become widely used such as thinking of how much is "externalized" in a particular representation and how. sdw -- swilliams@h... http://www.hpti.com Per: sdw@l... http://sdw.st Stephen D. Williams 703-371-9362C 703-995-0407Fax 20147 AIM: sdw
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