Data model
The central entity types of the datamodel are lexical units and senses. They connect the morpho-syntactic and semantical data in the data model. In essence the model is designed to be a multilingual model, however, currently it is used as a monolingual model that connects with multilingual data (which does not have the same level of granularity) via special entity types.
On the top level the model can be divided into clusters (color-coded in the model):
- lexical units (olive green)
- senses (blue)
- word forms (forest green)
- syntactic structures (brown)
- corpus examples (yellow)
- sense translations (red)
- sense frames (violet)
- resource connections (orange)
- generic features (grey)
- entity types that reference other entity types via meta-attributes (white)
The corpus data is not contained in the database itself, but is referenced and accessed via a concordancer. Some data (e.g., structure details) is defined in XML, which is used in existing processing pipelines. This data is stored in a separate generic SQL table, but can be remodeled if needed.
Contents
Overview
Purpose and state of this document
This document is intended for technical users who are working with the DDD model and/or backups. For
a higher-level, more theoretical and more linguistic description of the data model, see
here (which is currently very
brief, but will be expanded). For programmers who will also use the DDD Django repository, see the
README_code.md there (yet to be written, for now see README_datamodel_old.md).
The document was written for DDD model v1.15 and in line with DDD backup v3.3.
Database technology
The Digital Dictionary Database is a PostgreSQL database. It contains core tables (with prefix "jedro_"), metadata tables (with prefix "metadata_") and internal tables managed by Django and other integrated packages (with prefixes "django_", "auth_", etc.). The core tables contain the Slovene linguistic data, while the metadata tables refer to the core tables and contain data which are not considered part of the language description, but which are needed for central applications (e.g., longer names for dictionaries to display in the database editor).
We define and manage the database via the Django ORM. Partly for this reason, all tables have a single rather than composite primary key (docs). Also, we make use of Django's content types and generic relations (docs), which allow us to associate some simple extra data related to any table without adding lots of new columns or many-to-many tables. However, this means that special care needs to be taken with this data if using the database outside of Django.
Furthermore, for several reasons, some data is more naturally stored in other formats. However, they are still technically part of the SQL database, so that all the data is in one place and so that SQL transactions can encompass changes to this data. They are stored as whole strings in the "extension" table. Currently we have only two such extensions, both in XML format, and we intend to keep this to a minimum.
This readme focuses on the core data model, which is by far the most complex part of the database.
Core model diagram
MySQL WorkBench diagrams are used to develop and visualise the core of the data model. The project's main Django models.py file is (manually) kept in synch with diagram changes. The latest (v1.15) version of the data model is available here.
The diagram contains several color-coded clusters of tables. For a conceptual explanation of the domain, see here. This readme will provide a more technical explanation and interpretation of these tables and the key relationships between them. Note that the tables with a relatively dark colour shade in the diagram are just basic coding tables (with only id and name), so will not be covered here explicitly, unless they are of particular importance. Also note that every table in this model also has a last_modified timestamp column, but these are not included in the diagram to avoid repetitive clutter.
Model clusters
Lexical units
The main lexical unit table (LexicalUnit) is the central table in the database. Lexical units
consist of a type (LexicalUnitType), a syntactic structure (SyntacticStructure)
(ref), and one or more parts (LexicalUnit_Part). They are also
assigned categories (LexicalUnitCategory) and can be related to each other
(LexicalUnitRelation).
As (soon) explained
here, there are five
types of lexical unit, which fall under two broader categories: independent (single_lexeme_unit,
compound, phrase) and dependent (collocation, combination). For example, "miza" would be a
single_lexeme_unit, "okrogla miza" a compound, and "velika miza" a collocation. Independent
types are potential headwords with their own entries in dictionaries, while dependent units can be
included in the entries of headword units. At the level of the lexical unit tables, this difference
is usually irrelevant, but as we will see, the types do impact how associated data in some other
tables are interpreted (e.g., senses, resources).
Lexical unit parts correspond roughly to tokens in corpora. Usually these are words, but not always
(the 2nd part of "francosko-slovenski slovar" may correspond to the punctuation character -). In
the data model, LexicalUnit_Part connects the lexical unit of the part (LexicalUnit), the
component of that unit's syntactic structure the part corresponds to (StructureComponent), and the
form of the lexeme (FormEncoding) of that part. For instance, the first (of two) parts of "okrogla
miza" connect the lexical unit "okrogla miza" with the first component of the common adjective-noun
syntactic structure (ref) and the orthographic form of the appropriate form
(feminine singular nominative) of "okrogel" (ref).
A lexical unit is uniquely determined by its type, structure and sequence of parts. Therefore, we
cannot have multiple units which have the same combination of these properties, but we can have
multiple lexical units which only partially match. For example, we may have two units "švicarski
nož" (a compound and a phrase), or two noun single_lexeme_units for two forms of the same
lexeme ("oblast" and "oblasti").
Lexical units are further described by a lexicographic category (LexicalUnitCategory). These are
somewhat akin to the categories of lexemes (Category) ([ref][#bkmrk-word-forms]), and may
duplicate the same information for single_unit_lexemes. However, they are needed at this level for
lexical units with multiple parts to describe a multiword unit's category as a whole. For instance,
"okrogla miza" could be assigned a category of "noun phrase". Also, they can be useful to assign
lexical units which technically have multiple parts but conceptually have one to a simple category
(e.g., "covid-19" as a noun).
LexicalUnitRelations relate two lexical units with a particular relation type. The interpretation
is that for a given combination (from_lexical_unit, to_lexical_unit, type), to_lexical_unit
is a type for from_lexical_unit. If the relation is symmetric, it is stored twice, once in each
direction. (These conventions also apply for the other relation tables.)
Senses
While lexical units may be the most central unit in the data model, senses (Sense) are probably
the level to which the most data is attached. Lexical units have 1 or more senses, and each sense
belongs to a particular lexical unit. Senses can have definitions (Definition), they contain parts
(Sense_Part) and they can be related in various ways (SenseRelation). Certain relations can be
grouped into predefined clusters (SemanticClusterType). We can also store measures of sense
occurrences in corpora (Sense_Measure). And if we don't know which of several senses is
appropriate for some data, we can group alternatives (SenseCandidate).
Definitions are string descriptions of a sense. They are only used for independent lexical units,
for which they are the main aid in identifying senses for lexicographers and users. Definitions can
be of different types, among which indicator is the most common and important.
Each lexical unit has 1 or more senses with a particular (possibly null) position. However, their
interpretation depends on whether the lexical unit is dependent or independent
(ref). For independent lexical units, Senses with a non-null position are "real"
senses, normally equipped with further lexicographic data such as definitions or labels. The
positions determine the order of a lexical unit's senses, normally via lexicographers' explicit
decisions. But every independent lexical unit is also given a so-called "dummy" sense, which has
null position and is used when we want to associate sense-level data with a lexical unit, but we
don't yet know under which sense (which is a common situation because of the challenging nature of
automatic semantic categorisation etc.). In addition, if we know that some data corresponds to one
of a particular proper subset of a lexical unit's senses, we can also have a sense with null
position and candidate pairings (SenseCandidate), which relate particular senses (as
candidate_sense) to that sense (potential_sense). However, this sense candidate support has not
yet been put to use.
In (lexicographic) theory, dependent lexical units do not have senses, as indeed the main reason
they are "dependent" is that their meanings derive somehow from the meanings of their parts (compare
"okrogla miza" and "velika miza"). But from a technical point of view, since many kinds of data that
are attached to senses (e.g., translations, examples, labels) are relevant for both independent and
dependent units, dependent lexical units do have senses as well. For dependent lexical units, all
senses have null positions (their ordering in particular contexts is determined by calculable
criteria), and we do not anticipate to need sense candidates. However, a dependent lexical unit can
still have multiple senses, such as the literal and figurative meanings of the collocation "svinjski
jezik" (which will will have different translations, for example). Different senses of the same
dependent lexical unit are distinguished by their parts (SensePart) and dependency relations
(SenseRelation) (see below).
Sense parts (SensePart) serve two functions, identified by two different types. within_other
parts indicate which lexical unit parts of a dependent unit correspond to the sense of a particular
independent unit. For instance, the compound "okrogla miza" ("miza") is found in the 2nd and 3rd
parts of the collocation "organizirati okroglo mizo". (The reason that sense parts refer to senses
of independent units rather than the lexical units themselves is to make it easier to handle example
tokens (ref).) within_self parts, on the other hand, allow us to indicate the
role of the part in the sense (which is null for within_other parts). The roles are defined,
managed and assigned by lexicographers. In within_self parts, we are always connecting lexical
unit parts of a lexical unit with that lexical unit's own sense, which is redundant, but it does
simplify our data model as it prevents the need for creation of two similar tables.
Sense relations (SenseRelation) relate pairs of senses with a certain relation type. Senses of two
independent lexical units can be related with classic semantic relations (e.g. synonym, relating a
particular sense of "mali" with a particular sense of "majhen"). These relations always go in pairs;
for example, if "avto" is a hyponym for "vozilo", then "vozilo" is a hypernym for "avto". In
addition, a subsense relation, which indicates that one sense (to_sense) can be understood to be
a subsense of another (from_sense). Basic statistical data (e.g., degree of synonymity) can also
be stored (SenseRelation_Measure).
There is also a special relation type (dependency) which relates a dependent unit's sense
(to_sense) with an independent unit's sense (from_sense). For example, the literal sense of
"svinjski jezik" can be related to the physical senses of "svinjski" and "jezik", while its
metaphorical sense can be related to more abstract senses of "svinjski" and "jezik". We can also
have a sense of "svinjski jezik" which is not related to any independent unit senses, which would be
the "dummy" sense for the dependent lexical unit. Therefore, sense relations between senses of
independent lexical units give additional information about senses, while dependency sense relations
help define a dependent sense.
Dependent unit senses can also be organised in clusters under the independent senses which they are
related to. A set of cluster types (SemanticClusterType) is pre-defined for each lexical unit
category (LexicalUnitCategory). Each dependency sense relation can be assigned
(SenseRelationClusterType) to one of the cluster types of the independent unit's category. For
example, if the "noun" category has a "what material?" cluster type, then the "lesena miza"-"miza"
relation would be assigned to this category for the appropriate sense of the lexical unit "miza".
Sense measures (Sense_Measure) record basic statistical measure values for a sense in a particular
corpus. For instance, we would use this table to record that the physical sense of "svinjski jezik"
occurs in a particular corpus 157 times. If we are dealing with a corpus which has not been
semantically disambiguated, we can use the lexical unit's dummy sense (i.e., the position-less sense
of an independent unit or the relation-less sense of a dependent unit).
Word forms
Slovene is a highly inflectional language, where words have many forms with different sets of
features, so the data model includes a hierarchy of tables for morphological data. From top to
bottom, there are word grammatical categories (Category), form-independent lexemes of particular
categories (Lexeme), the set of morphosyntactic descriptions (MSDs) for each lexeme (WordForm),
concrete forms for such combinations (FormRepresentation) and actual string representations of
those concrete forms (FormEncoding). Word forms have a hierarchy of form representations of
different types, encoded as relations (FormRepresentationRelation). We can also store basic form
representation corpus statistics (FormRepresentation_Measure), and classify form representations
by their paradigm patterns (FormRepresentation_Pattern). Finally, lexemes also have canonical form
representations for each type (Lemma_FormRepresentation).
Lexemes (Lexeme) represent a word (or punctuation) consisting of a lemma (the basic or dictionary
form of the word) (e.g., "miza"), a category (e.g, "noun", "preposition", "punctuation") and a set
of category-dependent lexeme-level MSD (see below) features (e.g., noun gender)
(ref). This combination almost uniquely determines a lexeme, so we can
have two different lexemes with the same lemma (e.g., "dolg"), or even with the same lemma and
category (e.g., "klop"), but normally not with the same lemma, category and lexeme-level MSD
features. The exception is if we have differences in non-orthographic form representations (e.g.,
lesen (accentuation="lesén") and lesen(accentuation="lésen"). When these are encountered during
matching and we have to make a choice automatically, we can exclude the lexemes marked with the
feature "lexeme_homonym_secondary".
For a given lexeme, word forms (WordForm) are in effect abstract nodes for grouping together forms
under particular MSDs. MSDs (Msd) are linguistic codes which encode a particular combination of
morphosyntactic features morphosyntactic
description. For instance, Slovene nouns
typically have 18 word forms (6 cases x 3 numbers), so there are 18 Slovene MSDs for nouns. Each Msd
contains such a code, along with the features that are specific to particular forms (e.g., adjective
gender), but the word category and lexeme-level features are not stored at this level, as word forms
inherit them from their lexemes.
For each abstract word form, there is a hierarchy of form representations (FormRepresentation). We
currently have three different types of form representations: orthography (e.g., "dekan"),
accentuation (e.g., "dekàn") and pronunciation (e.g., "dɛˈkan"). Accentuation representations
fall under particular orthography representations, and pronunciation representations fall under
particular accentuation representations (e.g., "dɛˈkan" falls under "dekàn", not "dekán", although
they are all form representations corresponding to the MSD "Ncmsn"). These inter-type relationships
are encoded as relations (FormRepresentationRelation). In case there are multiple representations
of the same type for a given form, norm_status can be used to indicate the representation's
relative status (e.g., "non-standard", "variant").
The actual string representations of form representations are stored as form encodings
(FormEncoding). This is a separate level, because there can be multiple encodings for the same
representation using different encoding scripts. For instance, pronunciations can be encoded using
SAMPA or IPA, and in some languages even orthographic forms are commonly written with different
scripts (e.g., Cyrillic and Latin for Serbian).
As for senses, we can store basic corpus statistics at the level of form representations
(FormRepresentation_Measure). For instance, this table can record that the single genitive variant
"Shakespeareja" of the masculine lexeme "Shakespeare" occurs 123 times in Gigafida 2.0.
Also, form representations tend to follow certain paradigms (as typically described in grammar
books). These are managed by lexicographers and represented with pattern codes
(FormPattern). Individual form representations can then be assigned to particular patterns
(FormRepresentation_Pattern).
Finally, a lexeme's lemma can be explicitly associated with a subset of its form representations
(Lemma_FormRepresentation). This normally consists of all the form representations which fall
under a particular abstract word form, which is usually determined by the lexeme's category. For
example, for noun lexemes, this would be the representations falling under the singular nominative
word form. The lexeme's lemma should match one of the lexeme's orthography lemma representations.
Syntactic structures
Syntactic structures describe the structure of the canonical forms of lexical units. Each syntactic
structure (SyntacticStructure) defines a sequence of components (StructureComponent), their
properties, and dependencies between them. Structures can also be related to each other
(StructureRelation). Each lexical unit falls under a particular syntactic structure. However, most
of the details of syntactic structures are not stored in the SQL database, but rather in a related
XML extension file (static/extensions/structures.xml). There are several reasons for this (see
wiki). The format and contents of this
XML extension will not be covered here.
Structures (SyntacticStructure) have only an id, which serves primarily to connect the SQL core
and XML extension. New lexical units are normally assigned to particular syntactic structures with a
dedicated pipeline. The pipeline uses a standard parser (CLASSLA) together with scripts which match
the lexical unit's sequence of parts to a syntactic structure, and creates a new XML structure if
necessary. Such new structures are then added to the SQL database separately.
While most of the details of syntactic structures are kept in the XML, we do also register the
components in SQL (StructureComponent). The main reason for this is so we can efficiently access
the position (index) of the component within the structure, which is relevant when working with
LexicalUnitParts (ref).
We can associate structures with each other as relations (StructureRelation). For instance,
lexicographers may want to explicitly relate two structures which are similar except that the verb
is reflexive in one structure but not in the other (e.g., consider lexical units "umivati roke" in
"umivati si roke").
Corpus examples
Senses of lexical units can be associated with corpus text to demonstrate real usage. Corpora
(Corpus) are registered in the database. Examples (Example) always come from a particular corpus
and are comprised of sentences (ExampleSentence). A single example can apply to
different lexical units in particular senses (Sense_Example), and we track the tokens of those
lexical units within the examples (SenseExampleToken). Examples can be related to each other
(ExampleRelation).
Corpora (Corpus) are external resources of parsed text or speech and identified with a name and
version (e.g., Gigafida 2.0).
Examples (Example) are a sequence of sentences from a corpus that have been chosen to exemplify
one or more lexical units. In most cases, they have only one sentence, but sometimes consist of
more, when more context is needed.
The sentences of an example (ExampleSentence) have an id internal to the corpus, and a position
within the example. With the use of an external API, the id can be used to fetch the structured
sentence from the corpus in TEI format. Basic statistical data (e.g., quality of example) can also
be stored (ExampleSentence_Measure).
Senses of lexical units can be associated with a particular example (Sense_Example). The same
example can be used for different lexical units (e.g., "Organiziral je okroglo mizo." could be an
example for senses of "organizirati", "okrogla miza", "organizirati okroglo mizo", etc.).
We also track which tokens of an example represent the lexical unit (SenseExampleToken), which is
useful when visualising examples, such as marking the lexical unit in bold. For instance, if
"Organiziral je okroglo mizo." is used as an example for "okrogla miza", then in this table we would
note positions 3 and 4. However, for dependent lexical units (ref), we may also
want to differentiate between one of its independent lexical units and the rest. For instance, if
"Organiziral je okroglo mizo." is used as an example of "organizirati okroglo mizo" and we are
considering it as a collocation for "okrogla miza", then we might want to put, say, "okroglo mizo"
in bold and "organizirati" in italic. For this reason, the table also includes a SensePart
(ref): if the SensePart is of type within_other, then we can use it to make this
distinction.
Sense translations
The data model supports storage of translations from Slovene to other languages (Language) for
senses (Sense) and examples (Sense_Example) and may be in the form of an ordinary translation
(Translation) and/or explanation (Explanation). If the translations come from external sources
(ExternalSource), such as monolingual dictionaries of other languages, they can be associated with
translations (Translation_ExternalSource) along with an external id.
Since translations are used for both senses and examples, a more abstract table is also used
(Translation). A translation may be empty, in which case it should have at least one associated
explanation.
Explanations (Explanation) are alteratives to translations, and are normally a longer
description. They do not need to be in the same language as the Translation (this may depend, for
example, on the target users).
Translations are stored for senses (Sense_Translation) and examples
(SenseExample_Translation). Note that translations are not symmetric. For senses, the translation
will be analogous to the string of a lexical unit in the other language (and not a particular sense
of that unit). For examples, the text of the translation is stored directly in the database and the
lexical unit is not marked (ref).
Sense frames
Frames provide a formal description of a verb's semantic arguments. Frames (Frame) have components
(FrameComponent). The same abstract frame can be used by senses of different verbs
(Sense_Frame), for which components may have specific subroles (SenseFrame_Component). As this
part of the data model has not yet been used, it may well undergo further development.
In the model, frames (Frame) themselves are abstract elements with only ids. In addition to
providing foreign keys for related tables, these ids will also be used in a new xml extension for
semantic frames (analogous to ref).
Each frame has a set of frame components (FrameComponent). The components are of different types
corresponding to semantic roles (e.g., agent, experiencer, goal).
Senses of independent lexical units can be assigned to particular frames (Sense_Frame). For
example, a sense of dati might be associated with a frame which has an agent component for the
giver, a patient component for the object given and a recipient component for the recipient.
For particular verbs, frame components take on more specific roles than prescribed by their
component type (SenseFrame_Component). For instance, while agent components may generally include
any kind of animate objects, a verb like "plavati" is restricted to humans and animals.
Resource connections
In addition to storing lexical units and their diverse associated data, the data model also supports
the means to group (roughly speaking) subsets of this data for particular purposes (e.g., a
Slovene-Hungarian dictionary portal) and assign them statuses in that context. There are registry
tables for resources (Resource) and statuses (Status), and we can assign headword lexical units
to resources (LexicalUnit_Status) for valid combinations (Resource_Status), as well as
specifying relevant translation languages (Resource_Language). We can also specify if certain data
under headwords should be included in a resource and with what status (ResourceRelevance).
The resource table (Resource) just registers resources with a short name or acronym (e.g., "vsms"
for the Slovene-Hungarian dictionary). Each resource is typically associated with a relatively large
project or particular perspective on the database (model and/or data), and lexicographers may want
various imports or exports specific to that resource. There will often also be a particular portal
for a particular resource (VSMS), for which a
simplified resource-specific database is normally generated from the central database. If a resource
is a bilingual or multilingual dictionary, then it is assumed that the source language is Slovene,
and the target translation languages are explicitly stored (Resource_Language) (e.g., Hungarian
and Serbian for a dictionary resource with translations of Slovene units in Hungarian and
Serbian). There is also a special "ddd" resource, which represents a kind of meta-resource, as it
includes all the data (rather than just subsets as determined by lexicographers). For example,
whenever a new collocation is created, it is automatically included in this resource (see
ResourceRelevance explanation below).
The status table (Status) registers the global set of string statuses that are potentially
available to use for resource headwords (e.g., "manually-checked"). The actual statuses available
for a particular resource are then a subset of that (Resource_Status).
Independent lexical units can be "included" in a resource by assigning them a status of that
resource (LexicalUnit_Status). Doing so effectively makes them headwords for the resource. For
instance, if "miza" is assigned a particular status (e.g., "automatic") associated with the Sloleks
resource, then lexicographers will expect that "miza" will be a headword in the (generated) Sloleks
portal, perhaps marked in a particular way to signal that particular status. Note that dependent
lexical units cannot be assigned to a resource in this way, because by definition they cannot be
headwords but rather fall under them.
In order to specify if and how data subordinate to headwords should be included for particular
resources, a special Django feature is used (generic
relations, which
allows us to have one table (ResourceRelevance), rather than a separate one for each type of
subordinate data, to specify resource relevance. The content type (content_type_id) identifies the
appropriate table and the object's id (object_id) specifies its id within that table. Since some
types of objects (e.g., dependent lexical units) could fall under different headwords, headword_id
is used to explicitly specify the headword (e.g., we may want to include the collocation "velika
miza" under "miza" but not under "velik" for a particular resource). The inclusion_id and
status_id columns specify whether the data should be included and with with what status,
respectively.
However, in order to avoid the need for exhaustively adding and updating a ResourceRelevance row
for every single piece of subordinate data under every single headword in every single resource, a
set of agreed upon rules and defaults is applied. First, only specific preestablished kinds of data
can be selectively included in resources - at present these are headword senses, dependent unit
senses (which in practice means collocations and combinations), and sense examples. Second, the
default is that headword senses are included (ResourceRelevanceInclusion:include), while
dependent unit senses and sense examples are excluded
(ResourceRelevanceInclusion:exclude). Third, it is assumed that a default status is defined for
each resource (note that these statuses are different than the headword-levels ones in
Resource_Status). Under these assumptions, resource relevances only need to be defined for data if
it is of one of the specified types, and its inclusion and/or status are not the defaults. If the
columns contain null or the default for both columns, then it is the same (in the business logic) as
if the row is not included.
Generic features
In order to enable associating objects with particular features without promoting them to columns in
their tables (which may or may not be relevant for all objects in the table), the data model also
provides some tables for more generic purposes. Features (Feature) can be defined which take on a
set of values (FeatureValue) and are grouped into categories (FeatureCategory). Values can be
associated with objects (Object_Feature) and enter into relations (FeatureValueRelation). Also,
objects can be ordered for the sense under which they belong (SenseObjectOrder). Finally, playing
technically separate but conceptually similar function to features, the Measure table registers
statistical measures for data.
Every feature (Feature) has a name and belongs to a category (FeatureCategory), the combination
of which must be unique. Feature categories serve to group related features. In practice, we've used
categories with names that match the table that they are used with (e.g., sense_translation for
features which are only used with Sense_Translations), or the generic category general if a
feature is used with objects from multiple tables.
Feature values (FeatureValue) list all the allowed values (as strings) of a feature. The model
does not distinguish between theoretically close-ended features (e.g., "gender") and open-ended
features (e.g., "latin_name"); for the latter, extra feature values are just created as needed.
While features with their values are ultimately more or less equivalent to basic name-value pairs,
they can also be related to each other if needed. A particular case of this is with labels, where
there are two hierarchies of features: label_type and label_value. For instance, the
label_type feature has a value "domain", which is related to a subset of the label_value feature
(e.g., "zgodovina", "kemija", "organska kemija"), and these values have hierarchical relations
(e.g., "kemija" -> "organska kemija").
Using the same Django generic relation mechanism as ResourceRelevance
(ref), objects of any table in the core data model can then be
associated with one or more values of one or more features (Object_Feature). This is enabled with
a combination of two columns: content_type_id and object_id. content_type_id refers to
django's django_content_type table, where ids (id) are associated with table names (model),
while the object_id column specifies the id in that table. For example, if an Object_Feature has
content_type_id=18 and object_id=71, and the django_content_type table has model="sense" for
id=18, then the Object_Feature applies for the Sense with id=71. Note that an object can also
have multiple feature values, even (though rare) for the same feature.
In a similar fashion, the lexicographically relevant order of objects subordinate to the same sense
can be specified using a similar table which also uses the generic relation mechanism
(SenseObjectOrder). The orders are interpreted in the context of a particular table. For example,
we can specify the relative order of a sense's individual features, including its labels, semantic
types and other features, but these are all in one ordering list, since they are in the same table
(Object_Feature). Objects with no explicit order are interpreted as being in random order after
the ordered ones.
Finally, there is a separate registry table of measures (Measure), which can be used to record
basic statistical information for different kinds of data in particular corpora. The model supports
this for senses (Sense_Measure), form representations (FormRepresentation_Measure), example
sentences (ExampleSentence_Measure) and sense relations (SenseRelation_Measure).
Other formats
A special table (Extension) is used for data in other formats. The columns specify a unique
name, format (currently only XML is used), string with the string representation of the data,
and hash for that string representation. For example, one row in our current database contains the
details of the definitions of all syntactic structures, with @id attributes in synch with
SyntacticStructure ids. The hashes are derived using SHA512, which allows for more efficient
checks if data has changed.
These extensions allow for more flexibility in data representation and prevent a proliferation of special-purpose tables and columns, but we try to keep them to a minimum so that the vast majority of the database can be queried and manipulated via standard Django and SQL operations.
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