18 Feature Structures
內容
- 18.1 Organization of this Chapter
- 18.2 Elementary Feature Structures and the Binary Feature Value
- 18.3 Other Atomic Feature Values
- 18.4 Feature Libraries and Feature-Value Libraries
- 18.5 Feature Structures as Complex Feature Values
- 18.6 Re-entrant Feature Structures
- 18.7 Collections as Complex Feature Values
- 18.8 Feature Value Expressions
- 18.9 Default Values
- 18.10 Linking Text and Analysis
- 18.11 Feature System Declaration
- 18.12 Formal Definition and Implementation
A feature structure is a general purpose data structure which identifies and groups together individual features, each of which associates a name with one or more values. Because of the generality of feature structures, they can be used to represent many different kinds of information, but they are of particular usefulness in the representation of linguistic analyses, especially where such analyses are partial, or underspecified. Feature structures represent the interrelations among various pieces of information, and their instantiation in markup provides a metalanguage for the generic representation of analyses and interpretations. Moreover, this instantiation allows feature values to be of specific types, and for restrictions to be placed on the values for particular features, by means of feature system declarations.78
TEI: Organization of this Chapter¶18.1 Organization of this Chapter
This chapter is organized as follows. Following this introduction, section 18.2 Elementary Feature Structures and the Binary Feature Value introduces the elements fs and f, used to represent feature structures and features respectively, together with the elementary binary feature value. Section 18.3 Other Atomic Feature Values introduces elements for representing other kinds of atomic feature values such as symbolic, numeric, and string values. Section 18.4 Feature Libraries and Feature-Value Libraries introduces the notion of predefined libraries or groups of features or feature values along with methods for referencing their components. Section 18.5 Feature Structures as Complex Feature Values introduces complex values, in particular feature-structures as values, thus enabling feature structures to be recursively defined. Section 18.7 Collections as Complex Feature Values discusses other complex values, in particular values which are collections, organized as sets, bags, and lists. Section 18.8 Feature Value Expressions discusses how the operations of alternation, negation, and collection of feature values may be represented. Section 18.9 Default Values discusses ways of representing underspecified, default, or uncertain values. Section 18.10 Linking Text and Analysis discusses how analyses may be linked to other parts of an encoded text. Section 18.11 Feature System Declaration describes the feature system declaration, a construct which provides for the validation of typed feature structures. Formal definitions for all the elements introduced in this chapter are provided in section 18.12 Formal Definition and Implementation.
TEI: Elementary Feature Structures and the Binary Feature Value¶18.2 Elementary Feature Structures and the Binary Feature Value
The fundamental elements used to represent a feature structure analysis are f (for feature), which represents a feature-value pair, and fs (for feature structure), which represents a structure made up of such feature-value pairs. The fs element has an optional type attribute which may be used to represent typed feature structures, and may contain any number of f elements. An f element has a required name attribute and an associated value. The value may be simple: that is, a single binary, numeric, symbolic (i.e. taken from a restricted set of legal values), or string value, or a collection of such values, organized in various ways, for example, as a list; or it may be complex, that is, it may itself be a feature structure, thus providing a degree of recursion. Values may be under-specified or defaulted in various ways. These possibilities are all described in more detail in this and the following sections.
Feature and feature-value representations (including feature structure representations) may be embedded directly at any point in an XML document, or they may be collected together in special-purpose feature or feature-value libraries. The components of such libraries may then be referenced from other feature or feature-value representations, using the feats or fVal attribute as appropriate.
We begin by considering the simple case of a feature structure which contains binary-valued features only. The following three XML elements are needed to represent such a feature structure:
- fs (功能結構) 表示一個功能結構,即組織為一個結構單元的功能-值配對集合。
type 功能結構的類型。 feats (features) 參照組成該功能結構的功能值細節。 - f (功能) 表示一個功能值細節,即一項名稱與任一種不同類型值之間的關連。
name 功能名稱 fVal (feature value) 參照任何可用來代表功能值的元素。 - binary (二元值) 表示功能值細節的值部分資訊,可包含確切兩種可能值中的其中一種。
The attributes feats and the fVal are not discussed in this section: they provide an alternative way of indicating the content of an element, as further discussed in section 18.4 Feature Libraries and Feature-Value Libraries.
An fs element containing f elements with binary values can be straightforwardly used to encode the matrices of feature-value specifications for phonetic segments, such as the following for the English segment [s].
+--- ---+ | consonantal + | | vocalic - | | voiced - | | anterior + | | coronal + | | continuant + | | strident + | +--- ---+
<f name="consonantal">
<binary value="true"/>
</f>
<f name="vocalic">
<binary value="false"/>
</f>
<f name="voiced">
<binary value="false"/>
</f>
<f name="anterior">
<binary value="true"/>
</f>
<f name="coronal">
<binary value="true"/>
</f>
<f name="continuant">
<binary value="true"/>
</f>
<f name="strident">
<binary value="true"/>
</f>
</fs>
The restriction of specific features to specific types of values (e.g. the restriction of the feature strident to a binary value) requires additional validation, as does any restriction on the features available within a feature structure of a particular type (e.g. whether a feature structure of type phonological segment necessarily contains a feature voiced). Such validation may be carried out at the document level, using special purpose processing, at the schema level using additional validation rules, or at the declarative level, using an additional mechanism such as the feature-system declaration discussed in 18.11 Feature System Declaration.
Although we have used the term binary for this kind of value, and its representation in XML uses values such as true
and false
(or, equivalently, 1
and 0
), it should be noted that such values are not restricted to propositional assertions. As this example shows, this kind of value is intended for use with any binary-valued feature.
TEI: Other Atomic Feature Values¶18.3 Other Atomic Feature Values
Features may take other kinds of atomic value. In this section, we define elements which may be used to represent: symbolic values, numeric values, and string values. The module defined by this chapter allows for the specification of additional datatypes if necessary, by extending the underlying class model.featureVal.single. If this is done, it is recommended that only the basic W3C datatypes should be used; more complex datatyping should be represented as feature structures.
- symbol (符號值) 表示功能值細節的值部分資訊,包含限定符號列表中的其中一項。
value 提供功能的符號值,限定符號列表可在功能宣告中指明。 - numeric (數值) 表示功能值細節的值部分資訊,包含一個數值或數值範圍。
- string (字串值) 表示功能值細節的值部分資訊,包含一個字串。
<f name="case">
<symbol value="accusative"/>
</f>
<f name="gender">
<symbol value="feminine"/>
</f>
<f name="number">
<symbol value="plural"/>
</f>
</fs>
nominative
, genitive
, dative
, accusative
, etc.) and it is therefore appropriate to represent the values taken in this instance as symbol elements. Note that, instead of using a symbolic value for grammatical number, one could have named the feature singular or plural and given it an appropriate binary value, as in the following example: <f name="case">
<symbol value="accusative"/>
</f>
<f name="gender">
<symbol value="feminine"/>
</f>
<f name="singular">
<binary value="false"/>
</f>
</fs>
<f name="address">
<string>3418 East Third Street</string>
</f>
</fs>
<f name="houseNumber">
<numeric value="3418"/>
</f>
<f name="streetName">
<string>East Third Street</string>
</f>
</fs>
<f name="houseNumber">
<numeric value="3418" max="3440"/>
</f>
<f name="streetName">
<string>East Third Street</string>
</f>
</fs>
<f name="voice">active</f>
<f name="tense">SimPre</f>
</fs>
As noted above, additional processing is necessary to ensure that appropriate values are supplied for particular features, for example to ensure that the feature singular
is not given a value such as <symbol value="feminine"/>. There are two ways of attempting to ensure that only certain combinations of feature names and values are used. First, if the total number of legal combinations is relatively small, one can predefine all of them in a construct known as a feature library, and then reference the combination required using the feats attribute in the enclosing fs element, rather than give it explicitly. This method is suitable in the situation described above, since it requires specifying a total of only ten (5 + 3 + 2) combinations of features and values. Similarly, to ensure that only feature structures containing valid combinations of feature values are used, one can put definitions for all valid feature structures inside a feature value library (so called, since a feature structure may be the value of a feature). A total of 30 feature structures (5 × 3 × 2) is required to enumerate all the possible combinations of individual case, gender and number values in the preceding illustration. We discuss the use of such libraries and their representation in XML further in section 18.4 Feature Libraries and Feature-Value Libraries below.
However, the most general method of attempting to ensure that only legal combinations of feature names and values are used is to provide a feature-system declaration discussed in 18.11 Feature System Declaration.
<!--...-->
<f name="part_of_speech"
dcr:datcat="http://www.isocat.org/datcat/DC-1345" fVal="#commonNoun"
dcr:valueDatcat="http://www.isocat.org/datcat/DC-1256"/>
<!-- ... -->
</fs>
TEI: Feature Libraries and Feature-Value Libraries¶18.4 Feature Libraries and Feature-Value Libraries
As the examples in the preceding section suggest, the direct encoding of feature structures can be verbose. Moreover, it is often the case that particular feature-value combinations, or feature structures composed of them, are re-used in different analyses. To reduce the size and complexity of the task of encoding feature structures, one may use the feats attribute of the fs element to point to one or more of the feature-value specifications for that element. This indirect method of encoding feature structures presumes that the f elements are assigned unique xml:id values, and are collected together in fLib elements (feature libraries). In the same way, feature values of whatever type can be collected together in fvLib elements (feature-value libraries). If a feature has as its value a feature structure or other value which is predefined in this way, the fVal attribute may be used to point to it, as discussed in the next section. The following elements are used for representing feature libraries and feature-value libraries:
<f xml:id="CNS1" name="consonantal">
<binary value="true"/>
</f>
<f xml:id="CNS0" name="consonantal">
<binary value="false"/>
</f>
<f xml:id="VOC1" name="vocalic">
<binary value="true"/>
</f>
<f xml:id="VOC0" name="vocalic">
<binary value="false"/>
</f>
<f xml:id="VOI1" name="voiced">
<binary value="true"/>
</f>
<f xml:id="VOI0" name="voiced">
<binary value="false"/>
</f>
<f xml:id="ANT1" name="anterior">
<binary value="true"/>
</f>
<f xml:id="ANT0" name="anterior">
<binary value="false"/>
</f>
<f xml:id="COR1" name="coronal">
<binary value="true"/>
</f>
<f xml:id="COR0" name="coronal">
<binary value="false"/>
</f>
<f xml:id="CNT1" name="continuant">
<binary value="true"/>
</f>
<f xml:id="CNT0" name="continuant">
<binary value="false"/>
</f>
<f xml:id="STR1" name="strident">
<binary value="true"/>
</f>
<f xml:id="STR0" name="strident">
<binary value="false"/>
</f>
<!-- ... -->
</fLib>
/t/
, /d/
, /s/
, and /z/
may be defined as follows. <fs feats="#CNS1 #VOC0 #VOI1 #ANT1 #COR1 #CNT0 #STR0"/>
<fs feats="#CNS1 #VOC0 #VOI0 #ANT1 #COR1 #CNT1 #STR1"/>
<fs feats="#CNS1 #VOC0 #VOI1 #ANT1 #COR1 #CNT1 #STR1"/>
n="phonological segment definitions">
<!-- ... -->
<fs xml:id="T.DF"
feats="#CNS1 #VOC0 #VOI0 #ANT1 #COR1 #CNT0 #STR0"/>
<fs xml:id="D.DF"
feats="#CNS1 #VOC0 #VOI1 #ANT1 #COR1 #CNT0 #STR0"/>
<fs xml:id="S.DF"
feats="#CNS1 #VOC0 #VOI0 #ANT1 #COR1 #CNT1 #STR1"/>
<fs xml:id="Z.DF"
feats="#CNS1 #VOC0 #VOI1 #ANT1 #COR1 #CNT1 #STR1"/>
<!-- ... -->
</fvLib>
Feature structures stored in this way may also be associated with the text which they are intended to annotate, either by a link from the text (for example, using the TEI global ana attribute), or by means of stand-off annotation techniques (for example, using the TEI link element): see further section 18.10 Linking Text and Analysis below.
Note that when features or feature structures are linked to in this way, the result is effectively a copy of the item linked to into the place from which it is linked. This form of linking should be distinguished from the phenomenon of structure-sharing, where it is desired to indicate that some part of an annotation structure appears simultaneously in two or more places within the structure. This kind of annotation should be represented using the vLabel element, as discussed in 18.6 Re-entrant Feature Structures below.
TEI: Feature Structures as Complex Feature Values¶18.5 Feature Structures as Complex Feature Values
Features may have complex values as well as atomic ones; the simplest such complex value is represented by supplying a fs element as the content of an f element, or (equivalently) by supplying the identifier of an fs element as the value for the fVal attribute on the f element. Structures may be nested as deeply as appropriate, using this mechanism. For example, an fs element may contain or point to an f element, which may contain or point to an fs element, which may contain or point to an f element, and so on.
surface
, syntax
, and semantics
. The first of these has an atomic string value, but the other two have complex values, represented as nested feature structures of types category
and act
respectively: <f name="surface">
<string>love</string>
</f>
<f name="syntax">
<fs type="category">
<f name="pos">
<symbol value="verb"/>
</f>
<f name="val">
<symbol value="transitive"/>
</f>
</fs>
</f>
<f name="semantics">
<fs type="act">
<f name="rel">
<symbol value="LOVE"/>
</f>
</fs>
</f>
</fs>
verb
or transitive
. It might be preferable to replace these atomic feature values by feature structures. Suppose therefore that we maintain a feature-value library for each of the major syntactic categories (N, V, ADJ, PREP): <!-- ... -->
<fs xml:id="N" type="noun">
<!-- noun features defined here -->
</fs>
<fs xml:id="V" type="verb">
<!-- verb features defined here -->
</fs>
</fvLib>
N
, V
, etc.) to reference a complete definition for the corresponding feature structure. Each definition may be explicitly contained within the fs element, as a number of f elements. Alternatively, the relevant features may be referenced by their identifiers, supplied as the value of the feats attribute, as in these examples: <f xml:id="NN-1" name="nominal">
<binary value="true"/>
</f>
<f xml:id="NN-0" name="nominal">
<binary value="false"/>
</f>
<f xml:id="VV-1" name="verbal">
<binary value="true"/>
</f>
<f xml:id="VV-0" name="verbal">
<binary value="false"/>
</f>
<!-- ... -->
</fLib>
<f name="surface">
<string>love</string>
</f>
<f name="syntax">
<fs type="category">
<f name="pos" fVal="#V"/>
<f name="val" fVal="#TRNS"/>
</fs>
</f>
<f name="semantics">
<fs type="act">
<f name="rel" fVal="#LOVE"/>
</fs>
</f>
</fs>
Although in principle the fVal attribute could point to any kind of feature value, its use is not recommended for simple atomic values.
TEI: Re-entrant Feature Structures¶18.6 Re-entrant Feature Structures
Sometimes the same feature value is required at multiple places within a feature structure, in particular where the value is only partially specified at one or more places. The vLabel element is provided as a means of labelling each such re-entrancy point:
- vLabel (值標籤) 表示功能值細節的值部分資訊,這項值部分資訊出現在功能結構中一個以上的位置。
<f name="nominal">
<fs>
<f name="nm-num">
<vLabel name="L1">
<symbol value="singular"/>
</vLabel>
</f>
<!-- other nominal features -->
</fs>
</f>
<f name="verbal">
<fs>
<f name="vb-num">
<vLabel name="L1"/>
</f>
</fs>
<!-- other verbal features -->
</f>
</fs>
In the above encoding, the features named vb-num
and nm-num
exhibit structure sharing. Their values, given as vLabel
elements, are understood to be references to the same point in the feature structure, which is labelled by their name attribute.
NVAL1
.TEI: Collections as Complex Feature Values¶18.7 Collections as Complex Feature Values
Complex feature values need not always be represented as feature structures. Multiple values may also be organized as sets, bags or multisets, or lists of atomic values of any type. The vColl element is provided to represent such cases:
- vColl (值集合) 表示功能值細節的值部分資訊,包含形成一組、群組或一列表的複合值。
A feature whose value is regarded as a set, bag, or list may have any positive number of values as its content, or none at all, (thus allowing for representation of the empty set, bag, or list). The items in a list are ordered, and need not be distinct. The items in a set are not ordered, and must be distinct. The items in a bag are neither ordered nor distinct. Sets and bags are thus distinguished from lists in that the order in which the values are specified does not matter for the former, but does matter for the latter, while sets are distinguished from bags and lists in that repetitions of values do not count for the former but do count for the latter.
If no value is specified for the org attribute, the assumption is that the vColl defines a list of values. If the vColl element is empty, the assumption is that it represents the null list, set, or bag.
<f name="forenames">
<vColl>
<string>Daniel</string>
<string>Edouard</string>
</vColl>
</f>
<f name="mother" fVal="#p002"/>
<f name="father" fVal="#p009"/>
<f name="birthDate">
<fs type="date" feats="#y1988 #m04 #d17"/>
</f>
<f name="birthPlace" fVal="#austintx"/>
<f name="siblings">
<vColl org="set">
<fs copyOf="#pnb005"/>
<fs copyOf="#prb001"/>
</vColl>
</f>
</fs>
In this example, the vColl element is first used to supply a list of ‘name’ feature values, which together constitute the ‘forenames’ feature. Other features are defined by reference to values which we assume are held in some external feature value library (not shown here). For example, the vColl element is used a second time to indicate that the persons's siblings should be regarded as constituting a set rather than a list. Each sibling is represented by a feature structure: in this example, each feature structure is a copy of one specified in the feature value library.
<f name="category">
<symbol value="verb"/>
</f>
<f name="tense">
<symbol value="present"/>
</f>
<f name="agreement">
<fs>
<f name="person">
<symbol value="third"/>
</f>
<f name="number">
<symbol value="singular"/>
</f>
</fs>
</f>
</fs>
<f name="category">
<symbol value="verb"/>
</f>
<f name="tense">
<symbol value="present"/>
</f>
<f name="agreement">
<vColl org="set">
<symbol value="third"/>
<symbol value="singular"/>
</vColl>
</f>
</fs>
<f name="lex">
<symbol value="auxquels"/>
</f>
<f name="maf">
<vColl org="list">
<fs>
<f name="cat">
<symbol value="prep"/>
</f>
</fs>
<fs>
<f name="cat">
<symbol value="pronoun"/>
</f>
<f name="kind">
<symbol value="rel"/>
</f>
<f name="num">
<symbol value="pl"/>
</f>
<f name="gender">
<symbol value="masc"/>
</f>
</fs>
</vColl>
</f>
</fs>
The set, bag, or list which has no members is known as the null (or empty) set, bag, or list. A vColl element with no content and with no value for its feats attribute is interpreted as referring to the null set, bag, or list, depending on the value of its org attribute.
p027
(above) had no siblings, we might specify the siblings feature as follows. A vColl element may also collect together one or more other vColl elements, if, for example one of the members of a set is itself a set, or if two lists are concatenated together. Note that such collections pay no attention to the contents of the nested vColl elements: if it is desired to produce the union of two sets, the vMerge element discussed below should be used to make a new collection from the two sets.
TEI: Feature Value Expressions¶18.8 Feature Value Expressions
It is sometimes desirable to express the value of a feature as the result of an operation over some other value (for example, as ‘not green’, or as ‘male or female’, or as the concatenation of two collections). Three special purpose elements are provided to represent disjunctive alternation, negation, and collection of values:
- vAlt (替換值) 表示功能值細節的值部分資訊,包含一組值,僅其中一個得為有效值。
- vNot (矛盾值) 所表示的功能值和其內容互相矛盾。
- vMerge (合併的值集合) 所表示的功能值是將子元素中的功能值合併的結果,所使用的組成方法在屬性org中標明。
TEI: Alternation¶18.8.1 Alternation
<vAlt>
<numeric value="2"/>
<numeric value="3"/>
</vAlt>
</f>
<vAlt>
<fs>
<f name="number.of.bathrooms">
<numeric value="2"/>
</f>
</fs>
<fs>
<f name="number.of.bedrooms">
<numeric value="2"/>
</f>
</fs>
</vAlt>
</f>
<vAlt>
<fs>
<f name="number.of.bathrooms">
<numeric value="2"/>
</f>
</fs>
<fs>
<f name="number.of.bedrooms">
<numeric value="2"/>
</f>
</fs>
<vColl>
<fs>
<f name="number.of.bathrooms">
<numeric value="2"/>
</f>
</fs>
<fs>
<f name="number.of.bedrooms">
<numeric value="2"/>
</f>
</fs>
</vColl>
</vAlt>
</f>
selling.points
to describe items that are mentioned to enhance a property's sales value, such as whether it has a pool or a good view. Now suppose for a particular listing, the selling points include an alarm system and a good view, and either a pool or a jacuzzi (but not both). This situation could be represented, using the vAlt element, as follows. <f name="selling.points">
<vColl org="set">
<string>alarm system</string>
<string>good view</string>
<vAlt>
<string>pool</string>
<string>jacuzzi</string>
</vAlt>
</vColl>
</f>
</fs>
<f name="selling.points">
<vColl org="set">
<vAlt>
<string>alarm system</string>
<string>good view</string>
</vAlt>
<vAlt>
<string>pool</string>
<string>jacuzzi</string>
</vAlt>
</vColl>
</f>
</fs>
If a large number of ambiguities or uncertainties need to be represented, involving a relatively small number of features and values, it is recommended that a stand-off technique, for example using the general-purpose alt element discussed in section 16.8 Alternation be used, rather than the special-purpose vAlt element.
TEI: Negation¶18.8.2 Negation
case
are declared to be nominative, genitive, dative, or accusative, whether in a TEI feature system declaration or by some other means. Then the following two specifications are equivalent: <vNot>
<symbol value="genitive"/>
</vNot>
</f>
(ii)
<f name="case">
<vAlt>
<symbol value="nominative"/>
<symbol value="dative"/>
<symbol value="accusative"/>
</vAlt>
</f>
If however no such system declaration is available, all that one can say about a feature specified via negation is that its value is something other than the negated value.
Negation is always applied to a feature value, rather than to a feature-value pair. The negation of an atomic value is the set of all other values which are possible for the feature.
Any kind of value can be negated, including collections (represented by a vColl elements) or feature structures (represented by fs elements). The negation of any complex value is understood to be the set of values which cannot be unified with it. Thus, for example, the negation of the feature structure F is understood to be the set of feature structures which are not unifiable with F. In the absence of a constraint mechanism such as the Feature System Declaration, the negation of a collection is anything that is not unifiable with it, including collections of different types and atomic values. It will generally be more useful to require that the organization of the negated value be the same as that of the original value, for example that a negated set is understood to mean the set which is a complement of the set, but such a requirement cannot be enforced in the absence of a constraint mechanism.
TEI: Collection of Values¶18.8.3 Collection of Values
The vMerge element can be used wherever a feature value can appear. It contains two or more feature values, all of which are to be collected together. The organization of the resulting collection is specified by the value of the org attribute, which need not necessarily be the same as that of its constituent values if these are collections. For example, one can change a list to a set, or vice versa.
<f name="genders">
<vColl org="set">
<symbol value="masculine"/>
<symbol value="feminine"/>
</vColl>
</f>
</fs>
<f name="genders">
<vMerge org="list">
<vColl org="set">
<symbol value="masculine"/>
<symbol value="feminine"/>
</vColl>
<symbol value="neuter"/>
</vMerge>
</f>
</fs>
TEI: Default Values¶18.9 Default Values
The value of a feature may be underspecified in a number of different ways. It may be null, unknown, or uncertain with respect to a range of known possibilities, as well as being defined as a negation or an alternation. As previously noted, the specification of the range of known possibilities for a given feature is not part of the current specification: in the TEI scheme, this information is conveyed by the feature system declaration. Using this, or some other system, we might specify (for example) that the range of values for an element includes symbols for masculine, feminine, and neuter, and that the default value is neuter. With such definitions available to us, it becomes possible to say that some feature takes the default value, or some unspecified value from the list. The following special element is provided for this purpose:
- default (預設功能值) 表示功能值細節的值部分資訊,包含一個預設值。
<f name="gender">
<vAlt>
<symbol value="feminine"/>
<symbol value="masculine"/>
<symbol value="neuter"/>
</vAlt>
</f>
<vAlt>
<symbol value="feminine"/>
<symbol value="masculine"/>
</vAlt>
</f>
TEI: Linking Text and Analysis¶18.10 Linking Text and Analysis
<w ana="#at0">The</w>
<w ana="#ajs">closest</w>
<w ana="#pnp">he</w>
<w ana="#vvd">came</w>
<w ana="#prp">to</w>
<w ana="#nn1">exercise</w>
<w ana="#vbd">was</w>
<w ana="#to0">to</w>
<w ana="#vvi">open</w>
<w ana="#crd">one</w>
<w ana="#nn1">eye</w>
<phr ana="#av0">
<w>every</w>
<w>so</w>
<w>often</w>
</phr>
<c ana="#pun">,</c>
<w ana="#cjs">if</w>
<w ana="#pni">someone</w>
<w ana="#vvd">entered</w>
<w ana="#at0">the</w>
<w ana="#nn1">room</w>
<!-- ... -->
</s>
<!-- ... -->
<fs xml:id="ajs"
type="grammatical_structure" feats="#wj #ds"/>
<fs xml:id="at0"
type="grammatical_structure" feats="#wl"/>
<fs xml:id="pnp"
type="grammatical_structure" feats="#wr #rp"/>
<fs xml:id="vvd"
type="grammatical_structure" feats="#wv #bv #fd"/>
<fs xml:id="prp"
type="grammatical_structure" feats="#wp #bp"/>
<fs xml:id="nnn"
type="grammatical_structure" feats="#wn #tc #ns"/>
<!-- ... -->
</fvLib>
<!-- ... -->
<f xml:id="fl-bv" name="verbbase">
<symbol value="main"/>
</f>
<f xml:id="fl-bp" name="prepbase">
<symbol value="lexical"/>
</f>
<f xml:id="fl-ds" name="degree">
<symbol value="superlative"/>
</f>
<f xml:id="fl-fd" name="verbform">
<symbol value="ed"/>
</f>
<f xml:id="fl-ns" name="number">
<symbol value="singular"/>
</f>
<f xml:id="fl-rp" name="prontype">
<symbol value="personal"/>
</f>
<f xml:id="fl-tc" name="nountype">
<symbol value="common"/>
</f>
<f xml:id="fl-wj" name="class">
<symbol value="adjective"/>
</f>
<f xml:id="fl-wl" name="class">
<symbol value="article"/>
</f>
<f xml:id="fl-wn" name="class">
<symbol value="noun"/>
</f>
<f xml:id="fl-wp" name="class">
<symbol value="preposition"/>
</f>
<f xml:id="fl-wr" name="class">
<symbol value="pronoun"/>
</f>
<f xml:id="fl-wv" name="class">
<symbol value="verb"/>
</f>
<!-- ... -->
</fLib>
<w xml:id="S1W1">
<c xml:id="S1W1C1">C</c>ae<c xml:id="S1W1C2">s</c>ar</w>
<w xml:id="S1W2">
<c xml:id="S1W2C1">s</c>ei<c xml:id="S1W2C2">z</c>e<c xml:id="S1W2C3">d</c>
</w>
<w xml:id="S1W3">con<c xml:id="S1W3C1">t</c>rol</w>.
</s>
<fvLib xml:id="FSL1"
n="phonological segment definitions">
<!-- as in previous example -->
</fvLib>
<linkGrp type="phonology">
<!-- ... -->
<link target="#S.DF #S1W3C1"/>
<link target="#Z.DF #S1W2C3"/>
<link target="#S.DF #S1W2C1"/>
<link target="#Z.DF #S1W2C2"/>
<!-- ... -->
</linkGrp>
<w xml:id="mds0901">The</w>
<w xml:id="mds0902">closest</w>
<w xml:id="mds0903">he</w>
<w xml:id="mds0904">came</w>
<w xml:id="mds0905">to</w>
<w xml:id="mds0906">exercise</w>
<!-- ... -->
</s>
<!-- ... -->
<link target="#mds0901 #at0"/>
<link target="#mds0902 #ajs"/>
<link target="#mds0903 #pnp"/>
<link target="#mds0904 #vvd"/>
<link target="#mds0905 #prp"/>
<link target="#mds0906 #nn1"/>
<link target="#mds0907 #vbd"/>
<link target="#mds0908 #to0"/>
<link target="#mds0909 #vvi"/>
<link target="#mds0910 #crd"/>
<!-- ... -->
</linkGrp>
TEI: Feature System Declaration¶18.11 Feature System Declaration
The Feature System Declaration (FSD) is intended for use in conjunction with a TEI-conforming text that makes use of fs (that is, feature structure) elements. The FSD serves three purposes:
- It provides a mechanism by which the encoder can list all of the feature names and feature values and give a prose description as to what each represents.
- It provides a mechanism by which the encoder can define constraints not only what it means to be a well-formed feature structure, but also valid feature structure, relative to a given theory stated in typed feature logic. These constraints may involve constraints on the range of a feature value, constraints on what features are valid within certain types of feature structures, or constraints that prevent the co-occurrence of certain feature-value pairs.
- It provides a mechanism by which the encoder can define the intended interpretation of underspecified feature structures. This involves defining default values (whether literal or computed) for missing features.
The scheme described in this chapter may be used to document any feature structure system, but is primarily intended for use with the feature structure representation defined by the ISO 24610-1:2006 standard, which corresponds with the recommendations presented in these Guidelines, 18 Feature Structures. This chapter relies upon, but does not reproduce, formal definitions and descriptions presented more thoroughly in the ISO standard, which should be consulted in case of ambiguity or uncertainty.
The FSD serves an important function in documenting precisely what the encoder intended by the system of feature structure markup used in an XML-encoded text. The FSD is also an important resource which standardizes the rules of inference used by software to validate the feature structure markup in a text, and to infer the full interpretation of underspecified feature structures.
The reader should be aware the terminology used in this document does not always closely follow conventional practice in formal logic, and may also diverge from practice in some linguistic applications of typed feature structures. In particular, the term ‘interpretation’ when applied to a feature structure is not an interpretation in the model-theoretic sense, but is instead a minimally informative (or equivalently, most general) extension of that feature structure that is consistent with a set of constraints declared by an FSD. In linguistic application, such a system of constraints is the principal means by which the grammar of some natural language is expressed. There is a great deal of disagreement as to what, if any, model-theoretic interpretation feature structures have in such applications, but the status of this formal kind of interpretation is not germane to the present document. Similarly, the term ‘valid’ is used here as elsewhere in these Guidelines to identify the syntactic state of well-formedness in the sense defined by the logic of typed feature structures itself, as distinct from and in addition to the ‘well-formedness’ that pertains at the level of this encoding standard. No appeal to any notion from formal semantics should be inferred.
We begin by describing how an encoded text is associated with one or more feature system declarations. The second, third, and fourth sections describe the overall structure of a feature system declaration and give details of how to encode its components. The final section offers a full example; fuller discussion of the reasoning behind FSDs and another complete example are provided in Langendoen and Simons (1995).
TEI: Linking a TEI Text to Feature System Declarations¶18.11.1 Linking a TEI Text to Feature System Declarations
In order for application software to use feature system declarations to aid in the automatic interpretation of encoded texts, or even for human readers to find the appropriate declarations which document the feature system used in markup, there must be a formal link from the encoded texts to the declarations. However, the schema which declares the syntax of the Feature System itself should be kept distinct from the feature structure schema, which is an application of that system.
A document containing typed feature structures may simply include a feature system declaration documenting those feature structures. A more usual scenario, however, is that the same feature system declaration (or parts of it) will be shared by many documents. In either case, an fsDecl element for each distinct type of feature structure used must be provided and associated with the type, which is the value used within each feature structure for its type attribute.
When the module defined in this chapter is included in an XML schema, the following elements become available:
- fsdDecl (功能系統宣告) 明確指出規範某特定功能結構類型的功能系統宣告。
- fsdLink (feature structure declaration link) associates the name of a typed feature structure with a feature structure declaration for it.
- fsDecl (功能結構宣告) 宣告一種功能結構類型。
The fsdDecl element may be supplied either within the header of a standard TEI document, or as a standalone document in its own right. It contains one or more fsdLink or fsDecl elements.
<teiHeader>
<fileDesc>
<!-- example -->
</fileDesc>
<encodingDesc>
<!-- ... -->
<fsdDecl>
<fsDecl type="gpsg">
<!-- information about this type -->
</fsDecl>
<fsDecl type="lex">
<!-- information about this type -->
</fsDecl>
</fsdDecl>
<!-- ... -->
</encodingDesc>
</teiHeader>
<text>
<body>
<!-- ... -->
<fs type="lex">
<!-- an instance of the typed feature structure "lex" -->
</fs>
<!-- ... -->
</body>
</text>
</TEI>
In this case there is an implicit link between the fs element and the corresponding fsDecl element because they share the same value for their type attribute and appear within the same document. This is a short cut for the more general case which requires a more explicit link provided by means of the fsdLink element, as demonstrated below.
<!-- ... --><fsdDecl>
<fsDecl type="gpsg" xml:id="GPSG">
<!-- information about this type -->
</fsDecl>
<fsDecl type="lex" xml:id="LEX">
<!-- information about this type -->
</fsDecl>
</fsdDecl>
<teiHeader>
<fileDesc>
<!-- doc2 -->
</fileDesc>
<encodingDesc>
<!-- ... -->
<fsdDecl>
<fsdLink type="gpsg"
target="example.xml#GPSG"/>
<fsdLink type="lexx"
target="example.xml#LEX"/>
</fsdDecl>
<!-- ... -->
</encodingDesc>
</teiHeader>
<text>
<body>
<!-- ... -->
<fs type="lexx">
<!-- an instance of the typed feature structure "lex" -->
</fs>
<!-- ... -->
</body>
</text>
</TEI>
A fsdDecl may be given, as above, within the encoding description of the teiHeader element of a TEI document containing typed feature structures. Alternatively, it may appear independently of any feature structures, as a document in its own right, possibly with its own teiHeader. These options are both possible because the element is a member of both the model.encodingDescPart class and the model.resourceLike class.
The current recommendations provide no way of enforcing uniqueness of the type values among fsdDecl elements, nor of requiring that every type value specified on a fs element be also declared on an fsdDecl element. Encoders requiring such constraints (which might have some obvious utility in assisting the consistency and accuracy of tagging) are recommended to develop tools to enforce them, using such mechanisms as Schematron assertions.
TEI: The Overall Structure of a Feature System Declaration¶18.11.2 The Overall Structure of a Feature System Declaration
A feature system declaration contains one or more feature structure declarations, each of which has up to three parts: an optional description (which gives a prose comment on what that type of feature structure encodes), an obligatory set of feature declarations (which specify range constraints and default values for the features in that type of structure), and optional feature structure constraints (which specify co-occurrence restrictions on feature values).
- fsDescr (功能系統描述 (在功能結構宣告中)) 描述在功能結構宣告中宣告的功能結構類型所代表的意義。
- fDecl (功能宣告) 宣告一項功能,指明名稱、機構、有效值範圍、以及依情況提供預設值。
- fsConstraints (功能結構限制) 指出完善功能結構的內容限制。
Feature declarations and feature structure constraints are described in the next two sections. Note that the specification of similar fsDecl elements can be simplified by devising an inheritance hierarchy for the feature structure types. Each fsDecl element may name one or more ‘basetypes’ from which it inherits feature declarations and constraints (these are often called ‘supertypes’). For instance, suppose that <fsDecl type="Basic"> contains <fDecl name="One"> and <fDecl name="Two">, and that <fsDecl type="Derived" baseTypes="Basic"> contains just <fDecl name="Three">. Then any instance of <fs type="Derived"> must include all three features. This is because <fsDecl type="Derived"> inherits the two feature declarations from <fsDecl type="Basic"> when it specifies a base type of Basic.
<fsDescr>Describes what this type of fs represents</fsDescr>
<fDecl name="featureOne">
<!-- The declaration for featureOne -->
</fDecl>
<fDecl name="featureTwo">
<!-- The declaration for featureTwo -->
</fDecl>
<fsConstraints>
<!-- The feature structure constraints go here -->
</fsConstraints>
</fsDecl>
The attribute baseTypes gives the name of one or more types from which this type inherits feature specifications and constraints; if this type includes a feature specification with the same name as one inherited from any of the types specified by this attribute, or if more than one specification of the same name is inherited, then the possible values of that feature is determined by unification. Similarly, the set of constraints applicable is derived by conjoining those specified explicitly within this element with those implied by the baseTypes attribute. When no base type is specified, no feature specification or constraint is inherited.
Although the present standard does provide for default feature values, feature inheritance is defined to be monotonic.
The process of combining constraints may result in a contradiction, for example if two specifications for the same feature specify disjoint ranges of values, and at least one such specification is mandatory. In such a case, there is no valid feature structure of the type being defined.
Every type specified by baseTypes must be a single word which is a legal XML name; for example, they cannot include whitespace or begin with digits. Multiple base types are separated with spaces, e.g. <fsDecl type="Sub" baseTypes="Super1 Super2">.
TEI: Feature Declarations¶18.11.3 Feature Declarations
Each feature is declared in an fDecl element whose name attribute identifies the feature being declared; this matches the name attribute of the f elements it declares. An fDecl has three parts: an optional prose description (which should explain what the feature and its values represent), an obligatory range specification (which declares what values the feature is allowed to have), and an optional default specification (which declares what default value should be supplied when the named feature does not appear in an fs). If, in a feature structure, a feature:
- is not optional (i.e., is obligatory),
- has no value provided, or the value default is provided (see ISO 24610-1, Subclause 5.10, Default Values, and
- either has no default specified, or has conditional defaults, none of the conditions on which is met,
then the value of this feature in the feature structure's most general valid extension is the most general value provided in its vRange, in the case of a unit organization, or the singleton set, bag, or list containing that element, in the case of a complex organization. If the feature:
- is optional,
- has no value provided, or the value default is provided, and
- either has a default specified, or has conditional defaults, one of the conditions on which is met,
then this feature does have a value in the feature structure's most general valid extension when it exists, namely the default value that pertains.
It is possible that a feature structure will not have a valid extension because the default value that pertains to a feature is not consistent with that feature's declared range. Additional tools are required for the enforcement of such criteria.
The following elements are used in feature system declarations:
- fDecl (功能宣告) 宣告一項功能,指明名稱、機構、有效值範圍、以及依情況提供預設值。
name 指出所宣告的功能名稱;並符合文件中元素f的屬性name。 optional 指出該功能值是否存在。 - fDescr (功能描述 (在功能結構宣告中) ) 描述被宣告的功能所代表的意義以及其功能值。
- vRange (功能值範圍) 定義有效功能值的範圍,使用fs、vAlt、或原始值格式;一個有效的功能值必須包含在指定範圍之內;若f包含多個值 (由屬性org所認可),則每個值皆必須以vRange納入。
- vDefault (預設值) 在功能結構不包含元素f以提供名稱的情況下,宣告使用預設值;若無條件限制,預設值會被指明為一個 (或,取決於所包含的元素fDecl中屬性org的屬性值) 多個元素fs或原始值;若有條件限制,則被指明為一個或多個元素<if>;若無任何預設值、或無條件符合,則採用屬性值 none。
- if 定義一個功能的條件預設值;該條件被指明為一個功能結構,且若在需要預設值的文本中包含該功能結構時,則表示條件符合。
- then 區分條件和元素if中的預設值,或是區分元素cond中的前提和結果。
The logic for validating feature values and for matching the conditions for supplying default values is based on the operation of subsumption. Subsumption is a standard operation in feature-structure-based formalisms. Informally, a feature structure FS subsumes all feature structures that are at least as informative as itself; that is, all feature structures that specify all of the feature values that FS does with values that are subsumed by the values that FS has, and that have all of the re-entrancies (see 18.6 Re-entrant Feature Structures) that FS does. (Carpenter (1992); see also Pereira (1987) and Shieber (1986)) A more formal definition is provided in ISO 24610-1:2006 .
Following the spirit of the informal definition above, we can extend subsumption in a straightforward way to cover alternation, negation, special primitive values, and the use of attributes in the markup. For instance, a vAlt containing the value v subsumes v. The negation of a value v (represented by means of the vNot element discussed in section 18.8.2 Negation) subsumes any value that is not v; for example <vNot><numeric value='0'/></vNot>
subsumes any numeric value other than zero. The value <fs type="X"/> subsumes any feature structure of type X, even if it is not valid.
<fDescr>inverted sentence</fDescr>
<vRange>
<vAlt>
<binary value="true"/>
<binary value="false"/>
</vAlt>
</vRange>
<vDefault>
<binary value="false"/>
</vDefault>
</fDecl>
The value range is specified as an alternation (more precisely, an exclusive disjunction), which can be represented by the binary feature value. That is, the value must be either true or false, but cannot be both or neither.
<fDescr>surface form of the conjunction</fDescr>
<vRange>
<vAlt>
<symbol value="and"/>
<symbol value="both"/>
<symbol value="but"/>
<symbol value="either"/>
<symbol value="neither"/>
<symbol value="nor"/>
<symbol value="or"/>
<symbol value="NIL"/>
</vAlt>
</vRange>
<vDefault>
<binary value="false"/>
</vDefault>
</fDecl>
<fDescr>surface form of the complementizer</fDescr>
<vRange>
<vAlt>
<symbol value="for"/>
<symbol value="that"/>
<symbol value="whether"/>
<symbol value="if"/>
<symbol value="NIL"/>
</vAlt>
</vRange>
<vDefault>
<if>
<fs>
<f name="VFORM">
<symbol value="INF"/>
</f>
<f name="SUBJ">
<binary value="true"/>
</f>
</fs>
<then/>
<symbol value="for"/>
</if>
</vDefault>
</fDecl>
<fDescr>agreement for person and number</fDescr>
<vRange>
<fs type="Agreement"/>
</vRange>
</fDecl>
<fDescr>word form of a preposition</fDescr>
<vRange>
<vNot>
<string/>
</vNot>
</vRange>
</fDecl>
<vNot><string/></vNot>
subsumes any string that is not the empty string.Note that the class model.featureVal includes all possible single feature values, including feature structures, alternations (vAlt) and complex collections (vColl).
TEI: Feature Structure Constraints¶18.11.4 Feature Structure Constraints
Ensuring the validity of feature structures may require much more than simply specifying the range of allowed values for each feature. There may be constraints on the co-occurrence of one feature value with the value of another feature in the same feature structure or in an embedded feature structure.
Such constraints on valid feature structures are expressed as a series of conditional and biconditional tests in the fsConstraints part of an fsDecl. A particular feature structure is valid only if it meets all the constraints. The cond element encodes the conventional if-then conditional of boolean logic which succeeds when both the antecedent and consequent are true, or whenever the antecedent is false. The bicond element encodes the biconditional (if and only if) operation of boolean logic. It succeeds only when the corresponding if-then conditionals in both directions are true. In feature structure constraints the antecedent and consequent are expressed as feature structures; they are considered true if they subsume (see section 18.11.3 Feature Declarations) the feature structure in question, but in the case of consequents, this truth is asserted rather than simply tested. That is to say, a conditional is enforced by determining that the antecedent does not (and will never) subsume the given feature structure, or by determining that the antecedent does subsume the given feature structure, and then unifying the consequent with it (the result of which, if successful, will be subsumed by the consequent). In practice, the enforcement of such constraints can result in periods in which the truth of a constraint with respect to a given feature structure is simply not known; in this case, the constraint must be persistently monitored as the feature structure becomes more informative until either its truth value is determined or computation fails for some other reason.
The following elements make up the fsConstraints part of an FSD:
- fsConstraints (功能結構限制) 指出完善功能結構的內容限制。
- cond (條件功能結構限制) 定義一個條件功能結構限制;結果和前提被指明為功能結構或功能結構群組;若前提和結果皆包含一個已知功能結構、或前提不包含,則結果符合需求。
- bicond (雙條件功能結構限制) 定義一個雙條件功能結構限制;結果和前提被指明為功能結構或功能結構群組;若兩者皆包含一個已知功能結構、或兩者皆不包含,則結果符合需求。
- then 區分條件和元素if中的預設值,或是區分元素cond中的前提和結果。
- iff 區分條件和元素bicond 裡的結果。
For an example of feature structure constraints, consider the following ‘feature co-occurrence restrictions’ extracted from the feature system for English proposed by Gazdar, et al. (1985:246–247):
[FCR 1: [+INV] → [+AUX, FIN]
FCR 7: [BAR 0] ≡ [N] & [V] & [SUBCAT]
FCR 8: [BAR 1] → ~[SUBCAT]]
<fs>
<f name="INV">
<binary value="true"/>
</f>
</fs>
<then/>
<fs>
<f name="AUX">
<binary value="true"/>
</f>
<f name="VFORM">
<symbol value="FIN"/>
</f>
</fs>
</cond>
<fs>
<f name="BAR">
<symbol value="0"/>
</f>
</fs>
<iff/>
<fs>
<f name="N">
<binary value="true"/>
</f>
<f name="V">
<binary value="true"/>
</f>
<f name="SUBCAT">
<binary value="true"/>
</f>
</fs>
</bicond>
<fs>
<f name="BAR">
<symbol value="1"/>
</f>
</fs>
<then/>
<fs>
<f name="SUBCAT">
<binary value="false"/>
</f>
</fs>
</cond>
Note that cond and bicond use the empty tags then and iff, respectively, to separate the antecedent and consequent. These are primarily for the sake of enhancing human readability.
TEI: A Complete Example¶18.11.5 A Complete Example
<teiHeader>
<fileDesc>
<titleStmt>
<title>A sample FSD based on an extract from Gazdar
et al.'s GPSG feature system for English</title>
<respStmt>
<resp>encoded by</resp>
<name>Gary F. Simons</name>
</respStmt>
</titleStmt>
<publicationStmt>
<p>This sample was first encoded by Gary F. Simons (Summer
Institute of Linguistics, Dallas, TX) on January 28, 1991.
Revised April 8, 1993 to match the specification of FSDs
in version P2 of the TEI Guidelines. Revised again December 2004 to
be consistent with the feature structure representation standard
jointly developed with ISO TC37/SC4.
</p>
</publicationStmt>
<sourceDesc>
<p>This sample FSD does not describe a complete feature
system. It is based on extracts from the feature system
for English presented in the appendix (pages 245–247) of
Generalized Phrase Structure Grammar, by Gazdar, Klein,
Pullum, and Sag (Harvard University Press, 1985).</p>
</sourceDesc>
</fileDesc>
</teiHeader>
<fsdDecl>
<fsDecl type="GPSG">
<fsDescr>Encodes a feature structure for the GPSG analysis
of English (after Gazdar, Klein, Pullum, and Sag)</fsDescr>
<fDecl name="INV">
<fDescr>inverted sentence</fDescr>
<vRange>
<vAlt>
<binary value="true"/>
<binary value="false"/>
</vAlt>
</vRange>
<vDefault>
<binary value="false"/>
</vDefault>
</fDecl>
<fDecl name="CONJ">
<fDescr>surface form of the conjunction</fDescr>
<vRange>
<vAlt>
<symbol value="and"/>
<symbol value="both"/>
<symbol value="but"/>
<symbol value="either"/>
<symbol value="neither"/>
<symbol value="nor"/>
<symbol value="or"/>
<symbol value="NIL"/>
</vAlt>
</vRange>
<vDefault>
<binary value="false"/>
</vDefault>
</fDecl>
<fDecl name="COMP">
<fDescr>surface form of the complementizer</fDescr>
<vRange>
<vAlt>
<symbol value="for"/>
<symbol value="that"/>
<symbol value="whether"/>
<symbol value="if"/>
<symbol value="NIL"/>
</vAlt>
</vRange>
<vDefault>
<if>
<fs>
<f name="VFORM">
<symbol value="INF"/>
</f>
<f name="SUBJ">
<binary value="true"/>
</f>
</fs>
<then/>
<symbol value="for"/>
</if>
</vDefault>
</fDecl>
<fDecl name="AGR">
<fDescr>agreement for person and number</fDescr>
<vRange>
<fs type="Agreement"/>
</vRange>
</fDecl>
<fDecl name="PFORM">
<fDescr>word form of a preposition</fDescr>
<vRange>
<vNot>
<string/>
</vNot>
</vRange>
</fDecl>
<fsConstraints>
<cond>
<fs>
<f name="INV">
<binary value="true"/>
</f>
</fs>
<then/>
<fs>
<f name="AUX">
<binary value="true"/>
</f>
<f name="VFORM">
<symbol value="FIN"/>
</f>
</fs>
</cond>
<bicond>
<fs>
<f name="BAR">
<symbol value="0"/>
</f>
</fs>
<iff/>
<fs>
<f name="N">
<binary value="true"/>
</f>
<f name="V">
<binary value="true"/>
</f>
<f name="SUBCAT">
<binary value="true"/>
</f>
</fs>
</bicond>
<cond>
<fs>
<f name="BAR">
<symbol value="1"/>
</f>
</fs>
<then/>
<fs>
<f name="SUBCAT">
<binary value="false"/>
</f>
</fs>
</cond>
</fsConstraints>
</fsDecl>
<fsDecl type="Agreement">
<fsDescr>This type of feature structure encodes the features
for subject-verb agreement in English</fsDescr>
<fDecl name="PERS">
<fDescr>person (first, second, or third)</fDescr>
<vRange>
<vAlt>
<symbol value="1"/>
<symbol value="2"/>
<symbol value="3"/>
</vAlt>
</vRange>
</fDecl>
<fDecl name="NUM">
<fDescr>number (singular or plural)</fDescr>
<vRange>
<vAlt>
<symbol value="sg"/>
<symbol value="pl"/>
</vAlt>
</vRange>
</fDecl>
</fsDecl>
</fsdDecl>
</TEI>
TEI: Formal Definition and Implementation¶18.12 Formal Definition and Implementation
This elements discussed in this chapter constitute a module of the TEI scheme which is formally defined as follows:
- 組件 iso-fs: 功能結構 (Feature Structures)
The selection and combination of modules to form a TEI schema is described in 1.2 Defining a TEI Schema.