Jesse, I don't agree with your analysis.
My view is as follows: 1) POM5 should have strategically located xs:any and xs:anyAttribute elements that give tools fair warning of future extensions. I wish POM4 had them, but such is life. As things are, the community seems in general to be comfortable with a small risk of breaking some fragile tools by making small changes to POM4. 2) Adding explicit elements next to xs:any is a far more user-friendly extensibility mechanism than creating a hodgepodge of namespaces and prefixes. 3) I understand the theoretical advantage in correctness of changing the schema URI for each new version, but I question the practical utility. I can't think of a use case in which it actually helps anything. --benson On Tue, Aug 2, 2011 at 8:00 AM, Jesse Glick <[email protected]> wrote: > On 07/31/2011 05:12 PM, Benson Margulies wrote: >> >> >> https://cwiki.apache.org/confluence/display/MAVEN/Moving+forward+with+the+POM+data+model > > "It would [...] be a bad idea to try to use namespaces as a versioning > technique." - if you want to allow Schema validation of the entire POM, I > think you have to do this. Otherwise you cannot add new (optional) elements > - lest older versions of Maven or plugins be confused by them - or remove > obsolete elements - lest older POMs suddenly fail to validate. Code building > a model from a range of versioned namespaces could choose to have a single > model for all of them, if the differences are minor and easily dealt with in > small if-then blocks, or could define new models for major revisions; this > is awkward but probably no worse than handling "undeclared" changes to an > existing schema. > > Anyway having to type <modelVersion>4.0.0</modelVersion> is no better than > xmlns="http://maven.apache.org/POM/4.0.0";, I think. At least the latter > means that a Schema-aware XML editor/IDE can assist you. > > What _is_ bad in Maven currently (at least as of 3.0.3) is that whereas > modelVersion is required, you are permitted to write the POM with no > namespace declaration at all. This means that any code inspecting or > modifying a POM has to have a (rarely used) code branch to deal with > no-namespace elements, which is cumbersome. > > Worse, Maven seems to have a different idea of what valid content is than > the schema says. For example, the schema says <xs:element > name="modelVersion" minOccurs="0" ...> but Maven will report "'modelVersion' > is missing." as a fatal error. Certainly there will be some semantic > constraints that XML Schema cannot capture - e.g. <groupId> can be omitted > from <project> if <parent> specifies it - but these ought to be minimized. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
