Universal Attributes

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Revision as of 22:56, 15 April 2009

Attributes are arcs linking a node to itself. In opposition to relations, they correspond to one-place predicates, i.e., functions that take a single argument. In UNL, attributes have been normally used to represent information conveyed by natural language grammatical categories (such as tense, mood, aspect, number, etc). The set of attributes, which is claimed to be universal, is defined in the UNL Specs and is not open to frequent additions.

Syntax

The syntax of attributes is defined as follows:

<attribute>	::=	"@"<attribute name>
<attribute name>	::=	<character>...
<character>	::=	{“a”,...,“z”,“_”}

where:
< > variable
" " terminal symbol
::=... is defined as ...
{ } disjunction ("or")
... to be repeated more than 0 times

Attribute names are always lower case words or expressions. Normally, English words ("past", "will") or mnemonic abbreviations ("def", "pl") are used for attribute labelling. No blank space is allowed inside an attribute name ('@double_quote').

Semantics

Attributes are annotations made to nodes or hypernodes of a UNL hypergraph. They denote the circumstances under which these nodes (or hypernodes) are used.

Attributes may convey three different kinds of information:

• The information on the role of the node in the UNL graph (as in the case for '@entry', that indicates the main (starting) node of a UNL directed graph);
• The information on the original co-text (i.e., the textual neighborhoods) from which the node was extracted (as in the case of '@parenthesis', that indicates that the node was originally represented between parentheses); and
• The information on the (external) context of the utterance (as in the case of '@past', that indicates that the node was used in a time before the speaker's one). In that sense, attributes include phenomena technically called “speech acts”, “propositional attitudes”, and many others associated to the idea of "deixis".