This is the public web page for the Efficient Extensible Interchange (EXI) Working Group of the Efficient XML Interchange (EXI) Format (Second Edition). Feb 11, The Efficient XML Interchange Working Group has published a W3C Recommendation of Efficient XML Interchange (EXI) Format (Second. , Efficient XML Interchange (EXI) Format (Second Edition) Recommendation. , Proposed Edited Recommendation. .
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There are certain content items whose value representation involve the use of string tables while other content items are represented using the encoding rule described in 7.
A summary list of changes made to this document since the last publication is available. This is optional, but can be used to test that uploading the schema files, and any new property values are accepted by the server. No two productions with the same non-terminal symbol on the left-hand-side are permitted to have the same event code. The life cycle of a string table spans the processing of a single EXI interchage. Status of this Document This section describes the status of this document at the effocient of its publication.
Can be used together with the strict option. The i -th part of an event code is encoded as an n -bit unsigned integer 7. Values in an EXI stream are packed into bytes most significant bit first. In complex type grammars, all productions of the form LeftHandSide: To reach the broadest set of small, mobile and embedded applications, simple, elegant approaches are preferred to large, analytical or complex ones.
Basic Concepts EXI achieves broad generality, flexibility, and performance, by unifying concepts from formal language theory and information theory into a single, relatively simple algorithm. In this case, we can not only take advantage of generic XML knowledge but also of knowledge that is specific to the type of documents being encoded.
The figure above shows in highlighted form uri and local-name items used throughout the entire example document. If the URL could not be resolved, the following response is returned:.
For more information about this, see the inforamtion about known problems. Downloading a schema has the advantage, that size of schema does not matter.
Efficient XML Interchange (EXI) Format (Second Edition) Publication History – W3C
Every event in the stream is encoded using the same set of encoding rules, which are summarized as follows:. His breadth of knowledge, depth of insight, ingenuity and courage to speak up constantly shed a light onto us whenever the group seemed to stray into a futile path of disagreements during the course.
Event codes are similar to Huffman codes [Huffman Coding]but are much simpler to compute and maintain. World Wide Web Consortium. The set-of-chars for a charClass that constitutes an atom is the set of characters specified by the charClass expression XS2.
After encoding the string value, it is added to both the associated “local” value string table partition and the global value string table partition.
Efficient XML Interchange (EXI) Format (Second Edition)
The former and latter aforementioned roles of EXI processors are called [Definition: Then combine the sequence of grammars using the grammar concatenation operator defined in section 8. Downloading a new XML schema file on server. Effkcient, prefix content items are assigned to Prefix partitions.
It follows that a schema-informed EXI encoding defines a way of representing an instance of an XML infoset relative to a template. Appendix B Infoset Mapping describes the mapping system in detail.
Efficient XML Interchange (EXI) Format 1.0 (Second Edition) is a W3C Recommendation
The second compressed stream contains all value channels that contain at most values. This additional requirement will enable better grouping and, consequently, better compactness. A note in section 8. In particular, this suggests that SE subject is expected to occur before SE bodyand that both of these SE events are expected to interxhange after any AT efticient.
The value of each xsi: The EXI header conveys format version information and may also include the set of options that were used during encoding.
Values typed formta integer with bounded range of or smaller are now represented as n interchwnge Unsigned Integers see section 7. Each time a production is removed from a grammar, the event codes of the other productions with the same non-terminal symbol on the left-hand-side MUST be adjusted to keep them contiguous if its removal has left the remaining productions with non-contiguous event codes. When the value of compression option is false and the value bit-packed is used for alignment optionsvalues typed as Boolean are represented using n -bit unsigned integer 7.
The EXI grammars describe which events may occur at each point in formaat EXI stream and associate an even code with intrechange one. Note also that if you want the option to enter a session in the middle of the flow to listen to the communication, you need to clear tables and buffers between each stanza, or you will not be able to decode the binary stream appropriately.
As indicated in the table above, intercjange are some event types that carry content with their event instances while other event types function as markers without content. The default blockSize is intentionally large but can be reduced for processing large documents on devices with limited memory. To understand how a given event code approximates the likelihood a given production will matched, it is useful to visualize the event codes for a set of production rules that have the same non-terminal symbol on the left-hand-side as a tree.
The default blockSize is intentionally large but can be reduced for processing large documents on devices with limited memory. Create a proto-grammar that describes the content model according to available schema information see section 8.
The document is comprised of two major parts. XBC was chartered to investigate the costs and benefits of an alternative form of XML, and formulate a way to objectively evaluate the potential of a substitute format for XML.
EXI processors may report an error if the application attempts to encode events that have been pruned from the grammar or may simply ignore these events. When a string value is not found in the global or “local” value partition, its string literal is encoded as a String see 7. All productions in the built-in Element grammars of the form LeftHandSide: The behavior of an EXI processor on an EXI stream with its first bit set to 0 followed by a version not corresponding to a version implemented by the processor is not constrained by this specification.
The target namespace for canonical schemas urn: The above production translates to the following rule for acquiring the charset of a posCharGroup. For example, the grammar productions below describe the events that can occur in a schema-informed EXI stream after the Start-Document SD event provided there are four global elements defined in the schema and assign an event code for each one.
The primary use case of pre-compression is to avoid a duplicate compression step when compression capability is built into the transport protocol. Also, patched versions such as described in Known problems should be placed in the same snapshot repository.