delphin.tdl¶

Classes and functions for parsing and inspecting TDL.

Type Description Language (TDL) is a declarative language for describing type systems, mainly for the creation of DELPH-IN HPSG grammars. TDL was originally described in Krieger and Schäfer, 1994 [KS1994], but it describes many features not in use by the DELPH-IN variant, such as disjunction. Copestake, 2002 [COP2002] better describes the subset in use by DELPH-IN, but this publication has become outdated to the current usage of TDL in DELPH-IN grammars and its TDL syntax description is inaccurate in places. It is, however, still a great resource for understanding the interpretation of TDL grammar descriptions. The TdlRfc page of the DELPH-IN Wiki contains the most up-to-date description of the TDL syntax used by DELPH-IN grammars, including features such as documentation strings and regular expressions.

Below is an example of a basic type from the English Resource Grammar (ERG):

basic_word := word_or_infl_rule & word_or_punct_rule &
  [ SYNSEM [ PHON.ONSET.--TL #tl,
             LKEYS.KEYREL [ CFROM #from,
                            CTO #to ] ],
    ORTH [ CLASS #class, FROM #from, TO #to, FORM #form ],
    TOKENS [ +LIST #tl & < [ +CLASS #class, +FROM #from, +FORM #form ], ... >,
             +LAST.+TO #to ] ].

The delphin.tdl module makes it easy to inspect what is written on definitions in Type Description Language (TDL), but it doesn’t interpret type hierarchies (such as by performing unification, subsumption calculations, or creating GLB types). That is, while it wouldn’t be useful for creating a parser, it is useful if you want to statically inspect the types in a grammar and the constraints they apply.

KS1994: Hans-Ulrich Krieger and Ulrich Schäfer. TDL: a type description language for constraint-based grammars. In Proceedings of the 15th conference on Computational linguistics, volume 2, pages 893–899. Association for Computational Linguistics, 1994.
COP2002: Ann Copestake. Implementing typed feature structure grammars, volume 110. CSLI publications Stanford, 2002.

Module Parameters ¶

Some aspects of TDL parsing can be customized per grammar, and the following module variables may be reassigned to accommodate those differences. For instance, in the ERG, the type used for list feature structures is *list*, while for Matrix-based grammars it is list. PyDelphin defaults to the values used by the ERG.

delphin.tdl.LIST_TYPE = '*list*'¶: type of lists in TDL

delphin.tdl.EMPTY_LIST_TYPE = '*null*'¶: type of list terminators

delphin.tdl.LIST_HEAD = 'FIRST'¶: feature for list items

delphin.tdl.LIST_TAIL = 'REST'¶: feature for list tails

delphin.tdl.DIFF_LIST_LIST = 'LIST'¶: feature for diff-list lists

delphin.tdl.DIFF_LIST_LAST = 'LAST'¶: feature for the last path in a diff-list

Functions ¶

delphin.tdl.iterparse(path, encoding='utf-8')[source]¶

Parse the TDL file at path and iteratively yield parse events.

Parse events are (event, object, lineno) tuples, where event is a string (“TypeDefinition”, “TypeAddendum”, “LexicalRuleDefinition”, “LetterSet”, “WildCard”, “BeginEnvironment”, “EndEnvironment”, “FileInclude”, “LineComment”, or “BlockComment”), object is the interpreted TDL object, and lineno is the line number where the entity began in path.

Parameters

path – path to a TDL file
encoding (str) – the encoding of the file (default: “utf-8”)

Yields

(event, object, lineno) tuples

Example

>>> lex = {}
>>> for event, obj, lineno in tdl.iterparse('erg/lexicon.tdl'):
...     if event == 'TypeDefinition':
...         lex[obj.identifier] = obj
...
>>> lex['eucalyptus_n1']['SYNSEM.LKEYS.KEYREL.PRED']
<String object (_eucalyptus_n_1_rel) at 140625748595960>

delphin.tdl.format(obj, indent=0)[source]¶

Serialize TDL objects to strings.

Parameters

obj – instance of Term, Conjunction, or TypeDefinition classes or subclasses
indent (int) – number of spaces to indent the formatted object

Returns

str – serialized form of obj

Example

>>> conj = tdl.Conjunction([
...     tdl.TypeIdentifier('lex-item'),
...     tdl.AVM([('SYNSEM.LOCAL.CAT.HEAD.MOD',
...               tdl.ConsList(end=tdl.EMPTY_LIST_TYPE))])
... ])
>>> t = tdl.TypeDefinition('non-mod-lex-item', conj)
>>> print(format(t))
non-mod-lex-item := lex-item &
  [ SYNSEM.LOCAL.CAT.HEAD.MOD < > ].

Classes ¶

The TDL entity classes are the objects returned by iterparse(), but they may also be used directly to build TDL structures, e.g., for serialization.

Terms ¶

class delphin.tdl.Term(docstring=None)[source]¶

Base class for the terms of a TDL conjunction.

All terms are defined to handle the binary ‘&’ operator, which puts both into a Conjunction:

>>> TypeIdentifier('a') & TypeIdentifier('b')
<Conjunction object at 140008950372168>

Parameters: docstring (str) – documentation string

docstring¶

documentation string

Type: str

class delphin.tdl.TypeTerm(string, docstring=None)[source]¶

Bases: delphin.tdl.Term, str

Base class for type terms (identifiers, strings and regexes).

This subclass of Term also inherits from str and forms the superclass of the string-based terms TypeIdentifier, String, and Regex. Its purpose is to handle the correct instantiation of both the Term and str supertypes and to define equality comparisons such that different kinds of type terms with the same string value are not considered equal:

>>> String('a') == String('a')
True
>>> String('a') == TypeIdentifier('a')
False

class delphin.tdl.TypeIdentifier(string, docstring=None)[source]¶

Bases: delphin.tdl.TypeTerm

Type identifiers, or type names.

Unlike other TypeTerms, TypeIdentifiers use case-insensitive comparisons:

>>> TypeIdentifier('MY-TYPE') == TypeIdentifier('my-type')
True

Parameters

string (str) – type name
docstring (str) – documentation string

docstring¶

documentation string

Type: str

class delphin.tdl.String(string, docstring=None)[source]¶

Bases: delphin.tdl.TypeTerm

Double-quoted strings.

Parameters

string (str) – type name
docstring (str) – documentation string

docstring¶

documentation string

Type: str

class delphin.tdl.Regex(string, docstring=None)[source]¶

Bases: delphin.tdl.TypeTerm

Regular expression patterns.

Parameters

string (str) – type name
docstring (str) – documentation string

docstring¶

documentation string

Type: str

class delphin.tdl.AVM(featvals=None, docstring=None)[source]¶

Bases: delphin.tfs.FeatureStructure, delphin.tdl.Term

A feature structure as used in TDL.

Parameters

featvals (list, dict) – a sequence of (attribute, value) pairs or an attribute to value mapping
docstring (str) – documentation string

docstring¶

documentation string

Type: str

features(expand=False)[source]¶

Return the list of tuples of feature paths and feature values.

Parameters: expand (bool) – if True, expand all feature paths

Example

>>> avm = AVM([('A.B', TypeIdentifier('1')),
...            ('A.C', TypeIdentifier('2')])
>>> avm.features()
[('A', <AVM object at ...>)]
>>> avm.features(expand=True)
[('A.B', <TypeIdentifier object (1) at ...>),
 ('A.C', <TypeIdentifier object (2) at ...>)]

normalize()[source]¶

Reduce trivial AVM conjunctions to just the AVM.

For example, in [ ATTR1 [ ATTR2 val ] ] the value of ATTR1 could be a conjunction with the sub-AVM [ ATTR2 val ]. This method removes the conjunction so the sub-AVM nests directly (equivalent to [ ATTR1.ATTR2 val ] in TDL).

class delphin.tdl.ConsList(values=None, end='*list*', docstring=None)[source]¶

Bases: delphin.tdl.AVM

AVM subclass for cons-lists (< ... >)

This provides a more intuitive interface for creating and accessing the values of list structures in TDL. Some combinations of the values and end parameters correspond to various TDL forms as described in the table below:

TDL form	values	end	state
`< >`	`None`	`EMPTY_LIST_TYPE`	closed
`< … >`	`None`	`LIST_TYPE`	open
`< a >`	`[a]`	`EMPTY_LIST_TYPE`	closed
`< a, b >`	`[a, b]`	`EMPTY_LIST_TYPE`	closed
`< a, … >`	`[a]`	`LIST_TYPE`	open
`< a . b >`	`[a]`	`b`	closed

Parameters

values (list) – a sequence of Conjunction or Term objects to be placed in the AVM of the list.
end (str, Conjunction, Term) – last item in the list (default: LIST_TYPE) which determines if the list is open or closed
docstring (str) – documentation string

terminated¶

if False, the list can be further extended by following the LIST_TAIL features.

Type: bool

docstring¶

documentation string

Type: str

append(value)[source]¶

Append an item to the end of an open ConsList.

Parameters: value (Conjunction, Term) – item to add
Raises: TDLError – when appending to a closed list

terminate(end)[source]¶

Set the value of the tail of the list.

Adding values via append() places them on the FIRST feature of some level of the feature structure (e.g., REST.FIRST), while terminate() places them on the final REST feature (e.g., REST.REST). If end is a Conjunction or Term, it is typically a Coreference, otherwise end is set to tdl.EMPTY_LIST_TYPE or tdl.LIST_TYPE. This method does not necessarily close the list; if end is tdl.LIST_TYPE, the list is left open, otherwise it is closed.

Parameters

end (str, Conjunction, Term) – value to
as the end of the list. (use) –

values()[source]¶: Return the list of values in the ConsList feature structure.

class delphin.tdl.DiffList(values=None, docstring=None)[source]¶

Bases: delphin.tdl.AVM

AVM subclass for diff-lists (<! ... !>)

As with ConsList, this provides a more intuitive interface for creating and accessing the values of list structures in TDL. Unlike ConsList, DiffLists are always closed lists with the last item coreferenced with the LAST feature, which allows for the joining of two diff-lists.

Parameters

values (list) – a sequence of Conjunction or Term objects to be placed in the AVM of the list
docstring (str) – documentation string

last¶

the feature path to the list position coreferenced by the value of the DIFF_LIST_LAST feature.

Type: str

docstring¶

documentation string

Type: str

values()[source]¶: Return the list of values in the DiffList feature structure.

class delphin.tdl.Coreference(identifier, docstring=None)[source]¶

Bases: delphin.tdl.Term

TDL coreferences, which represent re-entrancies in AVMs.

Parameters

identifier (str) – identifier or tag associated with the coreference; for internal use (e.g., in DiffList objects), the identifier may be None
docstring (str) – documentation string

identifier¶

corefernce identifier or tag

Type: str

docstring¶

documentation string

Type: str

Conjunctions ¶

class delphin.tdl.Conjunction(terms=None)[source]¶

Conjunction of TDL terms.

Parameters: terms (list) – sequence of Term objects

add(term)[source]¶

Add a term to the conjunction.

Parameters: term (Term, Conjunction) – term to add; if a Conjunction, all of its terms are added to the current conjunction.
Raises: TypeError – when term is an invalid type

features(expand=False)[source]¶: Return the list of feature-value pairs in the conjunction.

get(key, default=None)[source]¶

Get the value of attribute key in any AVM in the conjunction.

Parameters

key – attribute path to search
default – value to return if key is not defined on any AVM

normalize()[source]¶

Rearrange the conjunction to a conventional form.

This puts any coreference(s) first, followed by type terms, then followed by AVM(s) (including lists). AVMs are normalized via AVM.normalize().

string()[source]¶: Return the first string term in the conjunction, or None.

property terms¶: The list of terms in the conjunction.

types()[source]¶: Return the list of type terms in the conjunction.

Type and Instance Definitions ¶

class delphin.tdl.TypeDefinition(identifier, conjunction, docstring=None)[source]¶

A top-level Conjunction with an identifier.

Parameters

identifier (str) – type name
conjunction (Conjunction, Term) – type constraints
docstring (str) – documentation string

identifier¶

type identifier

Type: str

conjunction¶

type constraints

Type: Conjunction

docstring¶

documentation string

Type: str

documentation(level='first')[source]¶

Return the documentation of the type.

By default, this is the first docstring on a top-level term. By setting level to “top”, the list of all docstrings on top-level terms is returned, including the type’s docstring value, if not None, as the last item. The docstring for the type itself is available via TypeDefinition.docstring.

Parameters: level (str) – “first” or “top”
Returns: a single docstring or a list of docstrings

features(expand=False)[source]¶: Return the list of feature-value pairs in the conjunction.

property supertypes¶: The list of supertypes for the type.

class delphin.tdl.TypeAddendum(identifier, conjunction=None, docstring=None)[source]¶

Bases: delphin.tdl.TypeDefinition

An addendum to an existing type definition.

Type addenda, unlike type definitions, do not require supertypes, or even any feature constraints. An addendum, however, must have at least one supertype, AVM, or docstring.

Parameters

identifier (str) – type name
conjunction (Conjunction, Term) – type constraints
docstring (str) – documentation string

identifier¶

type identifier

Type: str

conjunction¶

type constraints

Type: Conjunction

docstring¶

documentation string

Type: str

class delphin.tdl.LexicalRuleDefinition(identifier, affix_type, patterns, conjunction, **kwargs)[source]¶

Bases: delphin.tdl.TypeDefinition

An inflecting lexical rule definition.

Parameters

identifier (str) – type name
affix_type (str) – “prefix” or “suffix”
patterns (list) – sequence of (match, replacement) pairs
conjunction (Conjunction, Term) – conjunction of constraints applied by the rule
docstring (str) – documentation string

identifier¶

type identifier

Type: str

affix_type¶

“prefix” or “suffix”

Type: str

patterns¶

sequence of (match, replacement) pairs

Type: list

conjunction¶

type constraints

Type: Conjunction

docstring¶

documentation string

Type: str

Morphological Patterns ¶

class delphin.tdl.LetterSet(var, characters)[source]¶

A capturing character class for inflectional lexical rules.

LetterSets define a pattern (e.g., “!a”) that may match any one of its associated characters. Unlike WildCard patterns, LetterSet variables also appear in the replacement pattern of an affixing rule, where they insert the character matched by the corresponding letter set.

Parameters

var (str) – variable used in affixing rules (e.g., “!a”)
characters (str) – string or collection of characters that may match an input character

var¶

letter-set variable

Type: str

characters¶

characters included in the letter-set

Type: str

class delphin.tdl.WildCard(var, characters)[source]¶

A non-capturing character class for inflectional lexical rules.

WildCards define a pattern (e.g., “?a”) that may match any one of its associated characters. Unlike LetterSet patterns, WildCard variables may not appear in the replacement pattern of an affixing rule.

Parameters

var (str) – variable used in affixing rules (e.g., “!a”)
characters (str) – string or collection of characters that may match an input character

var¶

wild-card variable

Type: str

characters¶

characters included in the wild-card

Type: str

Environments and File Inclusion ¶

class delphin.tdl.TypeEnvironment(entries=None)[source]¶

TDL type environment.

Parameters: entries (list) – TDL entries

class delphin.tdl.InstanceEnvironment(status, entries=None)[source]¶

TDL instance environment.

Parameters

status (str) – status (e.g., “lex-rule”)
entries (list) – TDL entries

class delphin.tdl.FileInclude(value='', basedir='')[source]¶

Include other TDL files in the current environment.

Parameters

value – quoted value of the TDL include statement
basedir – directory containing the file with the include statement

value¶: The quoted value of TDL include statement.

path¶: The path to the TDL file to include.

Exceptions and Warnings ¶

exception delphin.tdl.TDLError(*args, **kwargs)[source]¶

Bases: delphin.exceptions.PyDelphinException

Raised when there is an error in processing TDL.

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

Bases: delphin.exceptions.PyDelphinSyntaxError

Raised when parsing TDL text fails.

exception delphin.tdl.TDLWarning(*args, **kwargs)[source]¶

Bases: delphin.exceptions.PyDelphinWarning

Raised when parsing unsupported TDL features.