C-command


In generative grammar and related frameworks, a node in a parse tree c-commands its sister node and all of its sister's descendants. In these frameworks, c-command plays a central role in defining and constraining operations such as syntactic movement, binding, and scope. Tanya Reinhart introduced c-command in 1976 as a key component of her theory of anaphora. The term is short for "constituent command".

Definition and examples

Standard Definition

Common terms to represent the relationships between nodes are below :
  • M is a parent or mother to A and B.
  • A and B are children or daughters of M.
  • A and B are sisters or siblings.
  • M is a grandparent or grandmother to C and D.
The standard definition of c-command is based partly on the relationship of dominance: Node N1 dominates node N2 if N1 is above N2 in the tree and one can trace a path from N1 to N2 moving only downwards in the tree ; that is, if N1 is a parent, grandparent, etc. of N2. For a node to c-command another node the parent of N1 must establish dominance over N2.
Based upon this definition of dominance, node N1 c-commands node N2 if and only if:
  • Node N1 does not dominate N2,
  • N2 does not dominate N1, and
  • The first branching node that dominates N1 also dominates N2.
For example, according to the standard definition, in the tree at the right,
  • M does not c-command any node because it dominates all other nodes.
  • A c-commands B, C, D, E, F, and G.
  • B c-commands A.
  • C c-commands D, F, and G.
  • D c-commands C and E.
  • E does not c-command any node because it does not have a sister node or any daughter nodes.
  • F c-commands G.
  • G c-commands F.
If node A c-commands node B, and B also c-commands A, it can be said that A symmetrically c-commands B. If A c-commands B but B does not c-command A, then A asymmetrically c-commands B. The notion of asymmetric c-command plays a major role in Richard S. Kayne's theory of Antisymmetry.

Where c-command is used

Standard Definition

A simplification of the standard definition on c-command is as follows:
A node A c-commands a node B iff
  • Neither A nor B dominates the other, and
  • Every branching node dominating A also dominates B
As such, we get sentences like:
Where John c-commands . This means that also c-commands and , which means that John c-commands both and .

Syntax Tree

In a parse tree, nodes A and B are replaced with a DP constituent, where the DP John c-commands DP he. In a more complex sentence, such as, the pronoun could interact with its antecedent and be interpreted in two ways.
In this example, two interpretations could be made:
In the first interpretation, John c-commands he and also co-references he. Co-reference is noted by the same subscript present under both of the DP nodes. The second interpretation shows that John c-commands he but does not co-reference the DP he. Since co-reference is not possible, there are different subscripts under the DP John and the DP he .

Definite Anaphora

Example sentences like these shows the basic relationship of pronouns with its antecedent expression. However, looking at definite anaphora where pronouns takes a definite descriptions as its antecedent, we see that pronouns with name cannot co-refer with its antecedent within its domain.
Where c-commands but i cannot co-refer to i*, and we can only interpret that someone else thinks that John is smart.
In response of the limits of c-command, Reinhart proposes a constraint on definite anaphora:

Binding Theory">Binding (linguistics)">Binding Theory

The notion of c-command can be found in frameworks such as Binding Theory, which shows the syntactic relationship between pronouns and its antecedent. The binding theory framework was first introduced by Chomsky in 1973 in relation to the treatment of various anaphoric phenomena, and has since been revised throughout the years. Chomsky's analysis places a constraint on the relationship between a pronoun and a variable antecedent. As such, a variable cannot be the antecedent of a pronoun to its left.
The first major revision to binding theory is found in Chomsky with their standard definitions:

Quantificational Binding

Compared to definite anaphora, quantificational expressions works differently and is more restrictive. As proposed by Reinhart in 1973, a quantificational expression must c-command any pronoun that it binds.
In this example, the quantifier c-commands the other pronoun and a bound variable reading is possible as the pronoun 'he' is bound by the universal quantifier 'every man'. The sentence in show two possible readings as a result of the bounding of pronouns with the universal quantifier. The reading in states that for all man, they each think that they are intelligent. Meanwhile, sentence state that for all men, they all think that someone is intelligent.
In general, for a pronoun to be bound by the quantifier and bound variable reading made possible, the quantifier must c-command the pronoun and both the quantifier and pronoun have to occur in the same sentence.

History

Relative to the history of the concept of c-command, one can identify two stages: analyses focused on applying c-command to solve specific problems relating to coreference and non-coreference; analyses which focused on c-command as a structural on a wide range of natural language phenomena that include but are not limited to tracking coreference and non-coreference.

Stage 1: Coreference

The development of ‘c-command’ is introduced by the notion of coreference. This is denoted by the first stage of the concept of c-command. In the initial emergence of coreference, Jackendoff. officially states...
If for any NP1 and NP2 in a sentence, there is no entry in the table NP2 + coref NP2, enter in the table NP1 - coref NP2
In other words, this rule states that any noun phrases that have not been associated with a coreference rule, are assumed to be noncoreferential. The tree to the right specifies this through the cyclical leftward movement of the pronoun and/or noun.
This is, then, edited by Lasnik in which...
NP1 cannot be interpreted as coreferential with NP2 iff NP1 precedes and commands NP2 and NP2 is not a pronoun. If NP1 precedes and commands NP2, and NP2 is not a pronoun, then NP1 and NP1 are noncoreferential.According to this rule, it is essential that NP2 be a pronoun for the sentence to be grammatical, despite NP1 being a pronoun or not. This can be shown through the examples below.
a) Lucy greets the customers she serves.
b) *She greets the customers Lucy serves.
c) *Lucy greets the customers Lucy serves.
d) She greets the customers she serves.
In this edition of coreference, Lasnik sets some restrictions on the permissible locations of NP1 and NP2, which hint at potential dominance.

Stage Two: Dominance

This leads to Stage 2 of the concept of c-command in which particular dominance is thoroughly explored. The term c-command was introduced by Tanya Reinhart in her 1976 dissertation and is a shortened form of constituent command. Reinhart thanks Nick Clements for suggesting both the term and its abbreviation. Reinhart states that...
A commands node B iff the branching node ⍺1 most immediately dominating A either dominates B or is immediately dominated by a node ⍺2 which dominates B, and ⍺2 is of the same category type as ⍺1
In other words, “⍺ c-commands β iff every branching node dominating ⍺ dominates β”
Chomsky adds a second layer to the previous edition of the c-command rule by introducing the requirement of maximal projections. He states...
⍺ c-commands β iff every maximal projection dominating ⍺ dominates β
This became known as "m-command."
The tree to the right compares the two definitions in this stage. Reinhart's "c-command" focuses on the branching nodes whereas Chomsky's "m-command" focuses on the maximal projections.
The current and widely used definition of c-command that Reinhart had developed was not new to syntax. Similar configurational notions had been circulating for more than a decade. In 1964, Klima defined a configurational relationship between nodes he labeled "in construction with". In addition, Langacker proposed a similar notion of "command" in 1969. Reinhart's definition has also shown close relations to Chomsky's 'superiority relation.'

Criticism and Alternatives

Over the years, the validity and importance of c-command for the theory of syntax have been widely debated. Linguists such as Benjamin Bruening have provided empirical data to prove that c-command is flawed and fails to predict whether or not pronouns are being used properly.

Bruening's take on c-command

In most cases, c-command correlates with precedence ; that is, if node A c-commands node B, it is usually the case that node A also precedes node B. Furthermore, basic SO word order in English correlates positively with a hierarchy of syntactic functions, subjects precede objects. Moreover, subjects typically precede objects in declarative sentences in English and related languages. Going back to Bruening, an argument is presented which suggests that theories of the syntax that build on c-command have misconstrued the importance of precedence and/or the hierarchy of grammatical functions. The grammatical rules of pronouns and the variable binding of pronouns that co-occur with quantified noun phrases and wh-phrases were originally grouped together and interpreted as being the same, but Bruening brings to light that there is a notable difference between the two and provides his own theory on this matter. Bruening suggests that the current function of c-command is inaccurate and concludes that what c-command is intended to address is more accurately analyzed in terms of precedence and grammatical functions. Furthermore, the c-command concept was developed primarily on the basis of syntactic phenomena of English, a language with relatively strict word order. When confronted with the much freer word order of many other languages, the insights provided by c-command are less compelling since linear order becomes less important.
As previously suggested, the phenomena that c-command is intended to address may be more plausibly examined in terms of linear order and a hierarchy of syntactic functions. Concerning the latter, some theories of syntax take a hierarchy of syntactic functions to be primitive. This is true of Head-Driven Phrase Structure Grammar, Lexical Functional Grammar, and dependency grammars. The hierarchy of syntactic functions that these frameworks posit is usually something like the following: SUBJECT > FIRST OBJECT > SECOND OBJECT > OBLIQUE OBJECT. Numerous mechanisms of syntax are then addressed in terms of this hierarchy