delphin.dmrs¶

Dependency Minimal Recursion Semantics ([DMRS])

DMRS: Copestake, Ann. Slacker Semantics: Why superficiality, dependency and avoidance of commitment can be the right way to go. In Proceedings of the 12th Conference of the European Chapter of the Association for Computational Linguistics, pages 1–9. Association for Computational Linguistics, 2009.

Serialization Formats¶

Module Constants¶

delphin.dmrs.FIRST_NODE_ID¶: The node identifier 10000 which is conventionally the first identifier used in a DMRS structure. This constant is mainly used for DMRS conversion or serialization.

delphin.dmrs.RESTRICTION_ROLE¶: The RSTR role used in links to select the restriction of a quantifier.

delphin.dmrs.EQ_POST¶: The EQ post-slash label on links that indicates the endpoints of a link share a scope.

delphin.dmrs.NEQ_POST¶: The NEQ post-slash label on links that indicates the endpoints of a link do not share a scope.

delphin.dmrs.HEQ_POST¶: The HEQ post-slash label on links that indicates the start node of a link immediately outscopes the end node.

delphin.dmrs.H_POST¶: The H post-slash label on links that indicates the start node of a link is qeq to the end node (i.e., start scopes over end, but not necessarily immediately).

delphin.dmrs.CVARSORT¶: The cvarsort dictionary key in Node.sortinfo that accesses the node’s type.

Classes¶

class delphin.dmrs.DMRS(top=None, index=None, nodes=None, links=None, lnk=None, surface=None, identifier=None)[source]¶

Bases: delphin.scope.ScopingSemanticStructure

Dependency Minimal Recursion Semantics (DMRS) class.

DMRS instances have a list of Node objects and a list of Link objects. The scopal top node may be set directly via a parameter or may be implicitly set via a /H Link from the special node id 0. If both are given, the link is ignored. The non-scopal top (index) node may only be set via the index parameter.

Parameters

top – the id of the scopal top node
index – the id of the non-scopal top node
nodes – an iterable of DMRS nodes
links – an iterable of DMRS links
lnk – surface alignment
surface – surface string
identifier – a discourse-utterance identifier

top¶: The scopal top node.

index¶: The non-scopal top node.

nodes¶: The list of Nodes (alias of predications).

links¶: The list of Links.

lnk¶: The surface alignment for the whole MRS.

surface¶: The surface string represented by the MRS.

identifier¶: A discourse-utterance identifier.

Example:

>>> rain = Node(10000, '_rain_v_1', type='e')
>>> heavy = Node(10001, '_heavy_a_1', type='e')
>>> arg1_link = Link(10000, 10001, role='ARG1', post='EQ')
>>> d = DMRS(top=10000, index=10000, [rain], [arg1_link])

arguments(types=None, expressed=None)[source]¶

Return a mapping of the argument structure.

When types is used, any DMRS Links with Link.attr set to H_POST or HEQ_POST are considered to have a type of ‘h’, so one can exclude scopal arguments by omitting ‘h’ on types. Otherwise an argument’s type is the Node.type of the link’s target.

Parameters

types – an iterable of predication types to include
expressed – if True, only include arguments to expressed predications; if False, only include those unexpressed; if None, include both

Returns

A mapping of predication ids to lists of (role, target) pairs for outgoing arguments for the predication.

is_quantifier(id)[source]¶: Return True if id is the id of a quantifier node.

properties(id)[source]¶: Return the morphosemantic properties for id.

quantification_pairs()[source]¶

Return a list of (Quantifiee, Quantifier) pairs.

Both the Quantifier and Quantifiee are Predication objects, unless they do not quantify or are not quantified by anything, in which case they are None. In well-formed and complete structures, the quantifiee will never be None.

Example

>>> [(p.predicate, q.predicate)
...  for p, q in m.quantification_pairs()]
[('_dog_n_1', '_the_q'), ('_bark_v_1', None)]

scopal_arguments(scopes=None)[source]¶

Return a mapping of the scopal argument structure.

The return value maps node ids to lists of scopal arguments as (role, scope_relation, target) triples. If scopes is given, the target is the scope label, otherwise it is the target node’s id. Only links with a Link.role value are considered, so MOD/EQ links are not included as scopal arguments.

Parameters: scopes – mapping of scope labels to lists of predications

Example

>>> d = DMRS(...)  # for "It doesn't rain.
>>> d.scopal_arguments()
{10000: [('ARG1', 'qeq', 10001)]}
>>> top, scopes = d.scopes()
>>> d.scopal_arguments(scopes=scopes)
{10000: [('ARG1', 'qeq', 'h2')]}

scopes()[source]¶

Return a tuple containing the top label and the scope map.

Note that the top label is different from top, which the top node’s id. If top does not select a top node, the None is returned for the top label.

The scope map is a dictionary mapping scope labels to the lists of predications sharing a scope.

class delphin.dmrs.Node(id, predicate, type=None, properties=None, carg=None, lnk=None, surface=None, base=None)[source]¶

Bases: delphin.sembase.Predication

A DMRS node.

Nodes are very simple predications for DMRSs. Nodes don’t have arguments or labels like delphin.mrs.EP objects, but they do have an attribute for CARGs and contain their vestigial variable type and properties in sortinfo.

Parameters

id – node identifier
predicate – semantic predicate
type – node type (corresponds to the intrinsic variable type in MRS)
properties – morphosemantic properties
carg – constant value (e.g., for named entities)
lnk – surface alignment
surface – surface string
base – base form

id¶: node identifier

predicate¶: semantic predicate

type¶: node type (corresponds to the intrinsic variable type in MRS)

properties¶: morphosemantic properties

sortinfo¶: properties with the node type at key “cvarsort”

carg¶: constant value (e.g., for named entities)

lnk¶: surface alignment

cfrom¶: surface alignment starting position

cto¶: surface alignment ending position

surface¶: surface string

base¶: base form

property sortinfo: Morphosemantic property mapping with cvarsort.

class delphin.dmrs.Link(start, end, role, post)[source]¶

Bases: object

DMRS-style dependency link.

Links are a way of representing arguments without variables. A Link encodes a start and end node, the role name, and the scopal relationship between the start and end (e.g. label equality, qeq, etc).

Parameters

start – node id of the start of the Link
end – node id of the end of the Link
role – role of the argument
post – “post-slash label” indicating the scopal relationship between the start and end of the Link; possible values are NEQ, EQ, HEQ, and H

start¶: node id of the start of the Link

end¶: node id of the end of the Link

role¶: role of the argument

post¶: “post-slash label” indicating the scopal relationship between the start and end of the Link

Module Functions¶

delphin.dmrs.from_mrs(m, representative_priority=None)[source]¶

Create a DMRS by converting from MRS m.

In order for MRS to DMRS conversion to work, the MRS must satisfy the intrinsic variable property (see delphin.mrs.has_intrinsic_variable_property()).

Parameters

m – the input MRS
representative_priority – a function for ranking candidate representative nodes; see scope.representatives()

Returns

DMRS

Raises

DMRSError when conversion fails. –

Exceptions¶

exception delphin.dmrs.DMRSSyntaxError(message=None, filename=None, lineno=None, offset=None, text=None)[source]¶

Bases: delphin.exceptions.PyDelphinSyntaxError

Raised when an invalid DMRS serialization is encountered.