the previous way to have models didn't work for most engines:
some have many keys one for each item.
bind a new DataModel into QML that will be associated to a specific DataSource and a key pattern

an exact one like "items" of rss
or a partial regexp one like "KnowledgeBase-[\d]*" like the ocs engine

in this way is not necessary to change how those dataengine works and is possible to use them in QML without headaches