Each XML document must have a unique root element (an element encompassing the entire document).
1	Each	each	DET	TOT-SG	_	3	det	_	_
2	XML	XML	PROPN	SG-NOM	Number=Sing	3	compound	_	_
3	document	document	NOUN	SG-NOM	Number=Sing	5	nsubj	_	_
4	must	must	AUX	PRES-AUX	VerbForm=Fin	5	aux	_	_
5	have	have	VERB	INF	VerbForm=Inf	0	root	_	_
6	a	a	DET	IND-SG	Definite=Ind|PronType=Art	9	det	_	_
7	unique	unique	ADJ	POS	Degree=Pos	8	amod	_	_
8	root	root	NOUN	SG-NOM	Number=Sing	9	compound	_	_
9	element	element	NOUN	SG-NOM	Number=Sing	5	obj	_	_
10	(	(	PUNCT	LeftParenthesis	_	12	punct	_	SpaceAfter=No
11	an	an	DET	IND-SG	Definite=Ind|PronType=Art	12	det	_	_
12	element	element	NOUN	SG-NOM	Number=Sing	9	appos	_	_
13	encompassing	encompass	VERB	ING	Tense=Pres|VerbForm=Part	12	acl	_	_
14	the	the	DET	DEF	Definite=Def|PronType=Art	16	det	_	_
15	entire	entire	ADJ	POS	Degree=Pos	16	amod	_	_
16	document	document	NOUN	SG-NOM	Number=Sing	13	obj	_	SpaceAfter=No
17	)	)	PUNCT	RightParenthesis	_	12	punct	_	SpaceAfter=No
18	.	.	PUNCT	Period	_	5	punct	_	_
