X-bar theory

The syntactic framework of the UNLarium derives from the X-bar theory , whose general structure is depicted below:

    XP
   / \
spec  XB
     / \
    XB  adjunct
   / \
  X   comp
  |
head

In the above:

• X is the head, the nucleus or the source of the whole syntactic structure, which is actually derived (or projected) out of it.
• comp (i.e., complement) is an internal argument, i.e., a word, phrase or clause which is necessary to the head to complete its meaning (e.g., objects of transitive verbs)
• adjunct is a word, phrase or clause which modifies the head but which is not syntactically required by it (adjuncts are expected to be extranuclear, i.e., removing an adjunct would leave a grammatically well-formed sentence)
• spec (i.e., specifier) is an external argument, i.e., a word, phrase or clause which qualifies (determines) the head
• XB (X-bar) is the general name for any of the intermediate projections derived from X
• XP (X-bar-bar, X-double-bar, X-phrase) is the maximal projection of X.

A key assumption of X-bar theory is that branching is always binary, if it occurs. This means that there can be as many XBs as necessary. Specifiers, complements and adjuncts are optional and are themselves syntactically complex, i.e., they correspond to XPs.

The X-bar theory is claimed to describe a universal principle of natural languages, which is subject to language specific parametrization concerning the order of the constituents (left specification x right specification, left adjunction x right adjunction, left complementation x right complementation), but not the role of constituents (specifier, adjunct, complement, head) or the possible heads.

In the UNLarium approach to the X-bar theory, the heads, which should replace the letter X, and which define the nature of the phrase, may be occupied by the following categories

• N = nominals (head of a #Noun Phrase or NP)
• V = verbs (head of a #Verbal Phrase or VP)
• J = adjectives (head of an #Adjective Phrase or JP)
• A = adverbs (head of an #Adverbial Phrase or AP)
• P = prepositions (head of a #Prepositional Phrase or PP)
• D = determiners (head of a #Determiner Phrase or DP)
• I = auxiliaries (head of an #Inflectional Phrase or IP)
• C = conjunctions (head of a #Complementizer Phrase or CP)

Noun phrase

According to the S-rule syntax, the basic x-bar structure can be represented as follows:

XP(XB(XB(head;complement);adjunct);spec)

For simplification reasons, the same structure can be represented by four head-driven relations, as follows:

XS(head;specifier), which describes the relation between the head of the structure and its specifier
XA(head;adjunct), which describes the relation between the head of the structure and its adjuncts
XC(head;complement), which describes the relation between the head of the structure and its complements
XP(head), which describes the head of the structure, without any reference to its internal structure

This is to say that:

XP(XB(XB(head;complement);adjunct);spec) = XS(head;specifier)XA(head;adjunct)XC(head;complement)

There can then nine syntactic roles in each phrase:

Tag	Syntactic Role	Description
XP	X phrase	maximal projection (used to make reference to the whole phrase without reference to its internal structure)
XS	relation between the head and the specifier	maximal projection (used to make reference to the presence of a specifier in the maximal projection)
XA	relation between the head and the adjunct	intermediate projection (used to make reference to the presence of an adjunct in the maximal projection)
XC	relation between the head and the complement	intermediate projection (used to make reference to the presence of a complement in the maximal projection)
SPEC	specifier	external argument (subject)
COMP	complement	internal argument (direct object, indirect object, etc.)
ADJT	adjunct	adjunct (adverbial and nominal adjuncts)
HEAD	head	noun head, adjective head, etc.

Lexical Categories

In the UNLarium framework, the set of lexical categories (X) which project phrasal categories (XP) are considered to be the following (in alphabetical order of head):

Tag	Category	Relations	Projections
J	Adjective	JC, JA, JS	JB, JP
A	Adverb	AC, AA, AS	AB, AP
C	Conjunction	CC, CA, CS	CB, CP
D	Determiner	DC, DA, DS	DB, DP
I	Inflection	IC, IA, IS	IB, IP
N	Noun	NC, NA, NS	NB, NP
P	Preposition	PC, PA, PS	PB, PP
V	Verb	VC, VA, VS	VB, VP

Syntactic hierarchy

The topmost level of the syntactic structure is sentence (SP), which is considered to be a maximal projection of the conjunction phrase (CP), which is the maximal projection of the inflectional phrase (IP), which is the maximal projection of a verbal phrase (VP). The other phrasal categories (NP, JP, AP, PP and DP) do not differentiate hierarchically.

 SP
 |
 CP   
 |
 IP
 |
 VP