Consider the following data, which illustrate an important fact about relative clauses headed by personal pronouns in German.

(1)		Ich, der ich sechzig bin,...	lit.:	'I, who I sixty am,...'
	*	Ich, der sechzig bin,...		'I, who sixty am,...'
	*	Ich, der sechzig ist,...		'I, who sixty is,...'
(2)		Du, der du sechzig bist,...		('you, sg.')
	*	Du, der sechzig bist,...
	*	Du, der sechzig ist,...
(3)	*	Er, der er sechzig ist,...		('he')
		Er, der sechzig ist,...
(4)	*	Sie, die sie sechzig ist,...		('she')
		Sie, die sechzig ist,...
(5)		Ihr, die ihr sechzig seid,...		('you, pl.')
	*	Ihr, die sechzig seid,...
	*	Ihr, die sechzig sind,...
(6)	*	Sie, die sie sechzig sind,...		('they')
		Sie, die sechzig sind,...

The facts above show the following: First and second person pronominal heads demand corresponding agreement morphology on the verb, i.e., default third person agreement is not permitted. At the same time, first and second person agreement morphology on the verb demands the presence, within the same clause, of a corresponding subject to agree with. This problem is resolved by repeating the pronoun that serves as the head of the relative as an internal subject precisely in such cases, i.e., precisely when needed to support non-third person singular agreement on the verb.

The task is to develop an optimality-theoretic analysis of these facts and generalizations by formulating the relevant constraints and ranking them in the correct way. In order to illustrate the analysis, tableaux should be provided for two or three suitable examples. No OT analysis is complete without a discussion of the factorial typology of its underlying constraint set, so it would also be important to briefly consider how corresponding agreement problems are resolved in other languages.

Finally, the attentive reader might have noticed that the facts for the first person plural have so far not been supplied. In this case, both forms are acceptable (even though the one with the additional wir sounds somewhat better).

(7)	Wir, die wir sechzig sind,...	('we')
	Wir, die sechzig sind,...

This additional evidence can, but need not, be taken into account in the solution. An analysis of the basic pattern should be in place before embarking on the treatment of such cases of optionality. Interesting further evidence along similar lines comes from paradigms with 1sg/3sg syncretism, where the two morphological categories share the same phonological form. Cases in point are verbs like wissen 'to know' or können 'to be able to':

(8)	Ich weiß	'I know'
	Ich kann	'I can'
	Er/sie/es weiß	'He/she/it knows'
	Er/sie/es kann	'He/she/it can'
	Du weißt	'You (sg.) know'
	Du kannst	'You (sg.) can'

Here both constructions are possible for the first person (but not for the second person):

(9)	Ich, der ich alles weiß,...
	Ich, der alles weiß,...
(10)	Ich, der ich alles kann,...
	Ich, der alles kann,...