Certainty and Responsibility

Encoders of text often find it useful to indicate that some aspects of the encoded text are problematic or uncertain, and to indicate who is responsible for various aspects of the markup of the electronic text. These Guidelines provide three methods of recording uncertainty about the text or its markup: the note element defined in section may be used with a value of certainty for its type attribute. the certainty element defined in this chapter may be used to record the nature and degree of the uncertainty in a more structured way. the alt element defined in the additional tag set for linking and segmentation may be used to provide alternative encodings for parts of a text, as described in section . There are three methods of indicating responsibility for different aspects of the electronic text: the TEI header records who is responsible for an electronic text by means of the respStmt element and other more specific elements (author, sponsor, funder, principal, etc.) used within the titleStmt, editionStmt, and revisionDesc elements. the note element may be used with a value of resp or responsibility in its type attribute. the respons element defined in this chapter may be used to record fine-grained structured information about responsibility for individual tags in the text. To use the note and respStmt elements, no special steps are needed, since they are defined in the core tag set and header respectively. The alt element is only available when the additional tag set for linking has been selected, as described in chapter . To use the certainty and respons elements, the additional tag set for certainty and responsibility must be selected; this is done by defining the parameter entity TEI.certainty with the value INCLUDE, as shown in the example below: ]> ... ]]>

Levels of Certainty

Many types of uncertainty may be distinguished. The certainty element is designed to encode the following sorts: a given tag may or may not correctly apply (e.g. a given word may be a personal name, or perhaps not) the precise point at which an element begins or ends is uncertain the value to be given for an attribute is uncertain content supplied by the encoder (such as the expansion of an abbreviation marked by the abbr tag) is uncertain the transcription of a source text is uncertain, perhaps because it is hard to read or hard to hear; this sort of uncertainty is also handled by the unclear element in section

The following types of uncertainty are not indicated with the certainty element: a number or date is imprecise the text is ambiguous, so a given passage has several possible interpretations a transcriber, editor, or author wishes to indicate a level of confidence in a factual assertion made in the text an author is not sure if the sentence she has chosen to start a paragraph is really the one she wants to retain in the final version Precision of numbers and dates is discussed in section ; well-defined ambiguity is handled with alternations in feature-structure values in chapter . Uncertainty about the truth of assertions in the text and other sorts of authorial and editorial uncertainty about whether the content is satisfactory are not handled by the certainty element, though they may be expressed using note.

Using Notes to Record Uncertainty

The simplest way of recording uncertainty about markup is to attach a note to the element or location about which one is unsure. In the following (invented) paragraph, for example, an encoder might be uncertain whether to mark Essex as a place name or a personal name, since both might be plausible in the given context: Elizabeth went to Essex. She had always liked Essex. Using note, the uncertainty here may be recorded quite simply: Elizabeth went to Essex. She had always liked Essex. It is not clear here whether Essex refers to the place or to the nobleman. -MSM ]]>

Using the normal mechanisms, the note may be associated unambiguously with specific elements of the text, thus: Elizabeth went to Essex. She had always liked Essex. It is not clear here whether Essex refers to the place or to the nobleman. If the latter, it should be tagged as a personal name. -MSM ]]>

The advantage of this technique is its relative simplicity. Its disadvantage is that the nature and degree of uncertainty are not conveyed in any systematic way and thus are not susceptible to any sort of automatic processing.

 Structured Indications of Uncertainty

To record uncertainty in a more structured way, susceptible of at least simple automatic processing, the certainty element may be used: indicates the degree of certainty or uncertainty associated with some aspect of the text markup. Attributes include: points at the elements whose markup is uncertain. indicates the precise location of the uncertainty in the markup: applicability of the element, precise position of the start- or end-tag, value of a specific attribute, etc. Suggested values include: the value given for the attribute name is uncertain. the content of the element may not have been correctly supplied by the reader, e.g. as in the cases of corr and abbrev elements. both the start-tag and the end-tag may not be correctly located. start-tag may not be correctly located. end-tag may not be correctly located. the content of the element may not be a correct transcription of the source text. uncertain whether the element used actually applies to the passage. indicates conditions assumed in the assignment of a degree of confidence. indicates the degree of confidence assigned to the aspect of the markup named by the locus attribute. provides an alternative value for the aspect of the markup in question---an alternative generic identifier, transcription, or attribute value, or the ID of an anchor element (to indicate an alternative starting or ending location). If an assertedValue is given, the confidence level specified by degree applies to the alternative markup specified by assertedValue; if none is given, it applies to the markup in the text. further describes the uncertainty in prose, perhaps indicating its nature, cause, or the justification for the degree of confidence asserted.

The certainty element may be used to record doubts about the proper encoding of Essex in several ways of varying precision. To record merely that we are not certain that Essex is in fact a place name, as it is tagged, we use the target attribute to identify the element in question, and the locus attribute to indicate what aspect of the markup we are uncertain about (here: whether we have used the correct element type): Essex. ]]> Because it is linked to the location of the uncertainty by an IDREF, the certainty element will typically be included in the same SGML document as its target. It may be placed adjacent to the target element, or elsewhere in the document.

To record the further information that we estimate, subjectively, that there is a 60 percent chance of Essex being a place name here, we can add a value for our degree of confidence (usually a number between 0 and 1, representing the estimated probability): Essex. ]]> According to one expert, there is a 60 percent chance of Essex being a place name here, and a 40 percent chance of its being a personal name. We use two certainty elements to indicate the two probabilities independently. Both elements indicate the same location in the text, but the second provides an alternative choice of generic identifier (here: persName) is given as the value of the assertedValue attribute: Essex. ]]>

Finally, we may wish to make our probability estimates contingent on some condition. In the passage Elizabeth went to Essex; she had always liked Essex, for example, we may feel there is a 60 percent chance that the county is meant, and a 40 percent chance that the earl is meant. But the two occurrences of the word are not independent: there is (we may feel) no chance at all that one occurrence refers to the county and one to the earl. We can express this by using the given attribute to list the SGML identifiers of certainty elements. Essex. She had always liked Essex. ]]> When given conditions are listed, the certainty element is interpreted as claiming a given degree of confidence in a particular markup given the assertional content of the certainty elements indicated---that is, if the markup described in the indicated certainty elements is correct.

Conditional confidence may be less that 100 percent: given the sentence Ernest went to old Saybrook, we may interpret Saybrook as a personal name or a place name, assigning a 60 percent probability to the former. If it is a place name, there may be a 50 percent chance that the place name actually in question is Old Saybrook rather than Saybrook, while if it is correctly tagged as a personal name, it is much more likely (say, 90 percent certain) that the name is Saybrook. This state of affairs can be expressed using the certainty element thus: old Saybrook. ]]> In this case, the assertedValue on certainty element c3 is an IDREF to an anchor element at the alternate starting point for the element.

Multiplying the numeric values out, this markup may be interpreted as assigning specific probabilities to three different ways of marking up the sentence: Saybrook. (0.6 * 0.9, or 0.54) Earnest went to old Saybrook. (0.4 * 0.5, or 0.20) Earnest went to old Saybrook. (0.4 * 0.5, or 0.20) ]]> The probabilities do not add up to 1.00 because the markup indicates that if Saybrook is (part of) a personal name, there is a 10 percent likelihood that the element should start somewhere other than the place indicated, without however giving an alternative location; there is thus a 6 percent chance (0.1 * 0.6) that none of the alternatives given is correct.

If an attribute value is uncertain, the locus attribute takes as its value the name of the attribute in question. In this example, there is only a 50 percent chance that the question was spoken by participant A: Have you heard the election results? ]]>

Doubts about whether the transcription is correct may be expressed by assigning to locus the value #transcribedContent. For example, if the source is hard to read and so the transcription is uncertain: gub. ]]>

Degrees of confidence in the proper expansion of abbreviations may also be expressed, by using the value #suppliedContent: Standard Generalized Markup Language ... ]]>

The assertedValue attribute should be used to provide an alternative value for whatever aspect of the markup is in doubt: an alternative generic identifier, or the ID of an alternative starting or ending point, as already shown, an alternative attribute value, or alternative element content, as in this example: gub. ]]> Since attribute values have no internal substructure, the assertedValue attribute is useful for specifying alternative transcriptions only in relatively restricted circumstances (specifically, when the alternate reading has no elements nested within it). More robust methods of handling uncertainties of transcription are the unclear element and the app and rdg elements described in chapter . The certainty element allows for indications of uncertainty to be structured with at least as much detail and clarity as appears to be currently required in most ongoing text projects. It is expected that in the future more adequate systems for expressing uncertainty will be developed. These may extend the certainty element or they may make use of the feature-structure encoding mechanisms described in chapter .

The certainty element and the other TEI mechanisms for indicating uncertainty provide a range of methods of graduated complexity. Simple expressions of uncertainty may be made by using the note element. This is simple and convenient, and can accommodate either discursive unstructured indication of uncertainty, or complex structured project-specific expressions of uncertainty. In general, however, unless special steps are taken, the note element does not provide as much expressive power as the certainty element, and in cases where highly structured certainty information must be given, it is recommended that the certainty element be used.

The certainty element may be used for simple unqualified indications of uncertainty, in which case only the locus and target might be specified. In more complex cases, the other attributes may be used to provide fuller information. While they may take any string of characters as value, the recommended values should be used wherever possible; if they are not appropriate in a given situation, encoders are should provide their own controlled vocabulary and document it in the encodingDesc or tagUsage elements of the TEI header.

The certainty element has the following formal declaration: ]]>

Attribution of Responsibility

In general, attribution of responsibility for the transcription and markup of an electronic text is made by respStmt elements within the header: specifically, within the title statement, the edition statement(s), and the revision history.

In some cases, however, more detailed element-by-element information may be desired, in order to distinguish, for example, between the individuals responsible for transcribing the content and those responsible for determining that a given word or phrase constitutes a proper noun. Where such fine-grained attribution of responsibility is required, the respons element may be used: identifies the individual(s) responsible for some aspect of the markup of some particular element(s). Attributes include: gives the SGML identifier(s) of the element(s) for which some aspect of the responsibility is being assigned. indicates the specific aspect of the markup for which responsibility is being assigned. Suggested values include: responsibility for the claim that the name attribute has the value given in the markup responsibility for the contents supplied by the encoder (corrections, expansions of abbreviations, etc.) responsibility for the claim that the element begins and ends where indicated responsibility for the claim that the element begins where indicated responsibility for the claim that the element ends where indicated responsibility for the transcription of the element content responsibility for the claim that the element is of the type indicated by the markup identifies the individual or agency responsible for the indicated aspect of the electronic text. gives a brief prose note supplying any additional information which should be recorded

This element allows one or more aspects of the markup to be attributed to a given individual. The target and locus attributes function as they do on the certainty element described in section : the target attribute points at a particular SGML element (or set of elements), and locus indicates the particular aspect of the encoding of those elements, for which responsibility is to be assigned. The suggested values may be combined as appropriate: to indicate, for example, that RC is responsible for transcribing an illegible word, and that AR is responsible for identifying that word as a proper noun, the text might be encoded thus: Saybrook. ]]>

Some elements bear specialized resp or agent attributes, which have specific meaning which varies from element to element; the respons element should be reserved for the general aspects of responsibility common to all text transcription and SGML markup, and should not be confused with the more specific attributes on individual elements.

The formal declaration of the respons element is this: ]]>