All Sitevision nodes are referenceable which means that the properties required by the specification are:
More information about these properties can be found in the JSR 283 specification.
According to JSR 283 - null properties are forbidden. If a property is added and it has a null value, it will be ignored (i.e. it will never exist). If you try to get a property and it doesn't exist, an Exception will be thrown.
Always use the PropertyUtil interface in the SiteVision utility API to read properties.
Performance is potentially better (uses internal calls whenever possible to bypass generic JCR calls) and no exceptions will be thrown (null is returned instead) when using PropertyUtil.
Metadata and node properties
Any metadata defined for a Sitevision object will be available as a property for the corresponding node. The property can be accessed via the metadata identifier name (i.e. "aName" in the example below)