Archive of UserLand's first discussion group, started October 5, 1998.

XML-RPC encoding issues

Author:Simeon Simeonov
Posted:1/17/1999; 9:18:10 AM
Topic:WDDX Annotated DTD
Msg #:2175 (In response to 2164)
Prev/Next:2174 / 2176


Dave, how can I quote the message I'm responding to?

[Dave] The first thing I'd like to consider is recordsets. I believe they can be mapped onto s, but I'll address that in a separate message.

[Sim] If you use structs you'll loose the type information. That's why WDDX has recordsets as a native datatype. Does Frontier have a native recordset datatype?

[Dave] About special characters, we use entity encoding. Like < and &. There must be a list of all the mappings. I'll go look for them, if anyone finds them, please chime in.

[Sim] This is not sufficient. XML defines "built-in" entity references for ampersand, greater-than, and less-than only. In UTF-8 you have to use character references for non 7-bit safe characters. This still does not address the issue of control characters that cannot be part of the content, regardless of whether they are represented by character references. That's why WDDX needs the char element. Finally, you have the issue of end-of-line handling and the fact that XML processors are required to translate carriage returns into newlines. Depending on what you need to do, your serializer needs to perform OS and language specific processing.

Robust data exchange using XML is not as easy as the press will have us think it is. :)

We've spend conderable amount of time researching and addressing these issues in WDDX. We've also thought about issues related to distributed data processing, e.g., timezone handling, type extensibility (via a new type= attribute coming in Beta2 of the WDDX SDK), etc. That, and the fact that WDDX has a clean superset of the types XML-RPC has, led to my proposal that we simply take the information XML-RPC needs and encode it in WDDX. It's the information that matters, not the encoding. This will save you the effort of doing all this work to improve the native XML-RPC encoding.

Whatever you decide to do, I'll be happy to be involved and help out as I can.


Sim, Allaire

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