Terminology

Here are some terms useful when discussing future extensibility.

• Round tripping involves the interchange of documents between different consumers/producers, as well as between different versions of the same consumer/producer. The pair of consumers/producers can be on the same or different platforms. Consider the case in which a document is created by the PML 2007. This document is then opened by PML 2003, edited, and saved. The edited document is now opened and used by PML 2007. In this case, the document originally created by PML 2007 has been round-tripped through PML 2003. It is also possible to round-trip a document created by PML 2003 through PML 2007.

• A Downrev (or down-level) version of a consumer/producer refers to one that understands an older version of a given schema. An Uprev (or up-level) version of a consumer/producer refers to one that understands a newer version of a given schema. The terms Downrev and Uprev are typically used in relative reference to one another. As an example, let's consider again, the two consumer/producer PML 2003 and PML 2007, where PML 2007 was released sometime after PML 2003, and, consequently, PML 2007 understands a newer revision of the DrawingML schema then does PML 2003. PML 2003 is referred to as the Downrev version while PML 2007 is referred to as the Uprev version. It is assumed that the Downrev version has less capability than the Uprev version.