1. XML Design for Streamability Roger L. Costello November 24, 2013 1

2. Design XML for Streaming? Philosophically I'm somewhat opposed to designing XML for streaming or for any particular process or processing paradigm. This is sometimes necessary, but more often I think it would be optimizing in the wrong place. Would you be comfortable if someone said you can't have cross-references in your user manual because they prevent you from streaming in your production process? I'd rather have the cross-references, and then if I need to stream, I can figure out how to do that. Wendell Piez xsl-list, 11/22/2013 2

3. Design XML for Streaming? Wendell makes a really good point. However, sometimes with a small tweak here and there, an XML design can be changed from one that is not streamable to one that is streamable. See next slide. 3

4. An XML Design That Is Not Suited For Streaming Below is an XML document that contains data about a military mission. It describes the type-of-mission (training, actual, simulation) and the weapons used. simulation CBU-89 20 Enemy terrorists 2013-05-11T08:00:00 Suppose that processing this requires knowing the type-of-mission. Since the type is in a preceding node (and XSLT streaming prohibits access to preceding nodes), the XSLT program cannot process WeaponRelease. 4

5. Revised XML Design So That It Is Suited For Streaming CBU-89 20 Enemy terrorists 2013-05-11T08:00:00 The data about the type-of-mission is now in an ancestor’s attribute, so the XSLT can process WeaponRelease. 5

6. Lesson Learned A simple change in XML design can make the difference between a streamable XML versus a non-streamable XML. 6