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Phonetics Laboratory
Faculty of Linguistics, Philology, and Phonetics

Data structure

The main data structure of IPOX is the metrical tree, or, more generally, a binary-branching, headed tree.


Type definition

Tree :: Node --> Tree

| ( Tree / Tree )
| ( Tree \ Tree )
| Terminal

In this definition, the slash is used to indicate which of two sister nodes is the (prosodic) head.


Graphic representations

  • conventional metrical tree: only weak-strong or strong-weak is indicated; unary nodes are ignored
  • headed constituent tree: constituent labels are shown, as well as headedness



two representations of the prosodic structure of the word photographical:

metrical tree headed tree

Internal representation

W --> 
(F --> (S --> "pho" \ S --> "to")
/ F --> ((S --> "gra" \ S --> "phi") \ S --> "cal"))

A node in a metrical representation is a complex feature structure (Shieber 1986).


Type definition

Node   ::  Category:Features

Features :: [FV*]

FV :: Node
| Feature=Value
| +Feature (Feature=true)
| -Feature (Feature=false)



complex feature structure for the unstressed vowel schwa

vow:[-stressed, voc:[+back, -rnd, height=mid]]

Our data structure is not limited to the representation of prosodic headedness.


Other uses

  • syntactic headedness:
    VP --> (V \ NP)
  • morphological structure:
    word --> ((prefix / root) \ suffix)



Our data structure is too general because prosodic structure is "flat", that is, non-recursive (Nespor and Vogel 1986).



  • self-embedding is OK if across the board , as in (a) below
  • self-embedding is compiled away in (b), obtaining (c)
  • a prosodic category may not dominate a category of a higher type


(a) (b) (c)

stress patterns of two Dutch words: (a) universiteit 'university'; (b=>c) makaroni 'macaroni'

Arthur Dirksen / adirksen@prl.philips.nl / January 13, 1995