So, to my understanding, the categories of German verbs are:
Weak: no irregularities in the formation of präteritum, past participles etc.
Strong: all verbs fall in one of the seven strong verb ablaut classes listed in Wiktionary (and also in this Stack Exchange thread) and differ in the formation of other tenses or declension.
Mixed (which I find very limited, is there an exhaustive list out there?): verbs that follow the general formation rules (e.g. ge+verb_stem+t for past participle) but have also some changes in the new verb stems they use, like denken, kennen, nennen etc.
Irregular, like sein and the modal verbs, which follow their own unique rules.
The predictability of the strong-verb ablaut classes makes them very appealing for my approach in the language, which is based more on the understanding of why things happen rather than pure memorization, but I’ve run into some problems.
The first is, that I am not certain that the lists of strong/irregular verbs out there are really exhaustive (also I think there is some confusion on the terminology as well, because ultimately not all irregular verbs are strong, yet many lists use the terms rather interchangeably). It would be really handy to have a list where all the irregulars verbs would be enumerated in the above manner, so one could see not only if a verb is strong, mixed, weak or irregular, but also to which of the seven ablaut classes it belongs.
The Wikipedia page is really difficult to handle because:
- It does not show all the verbs per class on one page.
- It contains loads of unnecessary prefixed versions of the same base verb which really elongates the total number of entries.
This of course applies only if, indeed, the aforementioned taxonomy of the four big classes of verbs is correct.
And secondly, there are some verbs I’ve encountered by chance, which add some more confusion to the whole matter. For example spalten isn’t registered as irregular in Wikipedia, yet its past participle is gespalten, not gespaltet. Are there many verbs in this kind of grey zone? Do they really fall in the completely irregular and unpredictable zone of the irregular verbs or are they linked to strong verbs?