XDS.b Implementation

This page is a placeholder for future XDS.b Implementation Notes
Rruggeri 15:49, 26 July 2007 (CDT)
If the Profile Implementation Template is useful feel free to use it. If not, feel free to improve it. :-))
kevino 12:26, 27 July 2007 (PDT)

Generating Proxies using SOAP Tools

There are some general guidelines to follow when generating proxies, especially for complex WSDL/schemas such as the ones included in XDS.b, that will make your life much, much easier.

The first one is use generic, non-strongly typed WSDL for development purposes, that is for the purpose of generating the proxy.
Strongly typed WSDL will force the infrastructure to go through all the xml type definitions and generate classes for them. The mapping between XSD and object oriented constructs is not always straightforward and you might run into some problems even with valid instances.
This approach works well for your average weather web service, but not for more complex scenarios like the ones we have to deal with.

Furthermore, generating classes through proxies will force turning the XML in the SOAP message to objects where most likely you will have to deal with the XML anyways. This step can also be somewhat resource intensive as it forces a validation of the whole message which is usually avoided in production environments with high transaction volume.

Generic WSDL for development replace the types of the input/output SOAP messages with generic xs:any types. By generating the proxy from that modified WSDL you get a method signature that basically only deals with raw XML documents for input and output. Yes, you lose "automatic" XSD validation, but you can always put that step back in if you want and make it optional when you go to production.

Transition from MTOM to MTOM/XOP

The XDS.b supplement, as published, documents the use of the MTOM [standard]. Now that the testing season has started, we have found that this choice of standards is not appropriate. This section documents the reason for the change and the necessary updates to the XDS.b supplement. This material will be formatted as a formal Change Proposal to the XDS.b profile later this season. These change will be in effect for January 2008 North American Connectathon.

Choice of Standards

In many ways XDS.b is a technology update to the original XDS (now called XDS.a). The move from SOAP with Attachments to MTOM is part of this update. In selecting MTOM as the replacement we thought we were tracking the industry correctly. The real situation is slightly more complicated. There are two relevant standards here, [MTOM] and [XOP] ([XOP FAQ]). As originally published, XDS.b references MTOM without XOP. This update changes that to be MTOM with XOP. This change is being made for the following reasons:

• In common/casual usage, from my own informal survey, the term MTOM is used to mean MTOM with XOP

• It is pretty hard to find discussion of MTOM without XOP.

• The following packages are known to support MTOM/XOP: Apache Axis2, .NET. My informal survey of web-available material indicates the same for JBOSS and Oracle.

• Several sites document performance issues when using MTOM without XOP when used with large attachments. From and XDS point of view this means large documents. I believe this comes from using XML parsers that are not optimized for dealing with such large text nodes within the XML. More on this below where I discuss technology issues.

• .NET ([documentation]) uses a strategy of using MTOM for small documents and MTOM/XOP for large documents.

Discussion of Standards

To understand this change one needs to understand parts of three standards:

• [MTOM]
• [XOP]

Change Proposal

See Also

Cross Enterprise Document Sharing

Cross-Enterprise Document Sharing Implementation