P5: Principes directeurs pour l'encodage et l'échange de textes électroniques

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 the first occurrence refers to the county and the second to the earl. We can express this by using the given attribute to list the identifiers of certainty elements. 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, a conjectural assertion is being made solely on the assumption that the interpretation indicated by the element named by the given attribute is actually 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’. Hence there is uncertainty about the correct location for the markup as well as about which markup to use. This state of affairs can be expressed using the certainty element thus: Note the use of the assertedValue on certainty elements cert3 and cert4 to reference the anchor element placed at the alternative 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: 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.

We may also wish to indicate confidence in some aspect of the tagging throughout a document, rather than (as discussed so far) in one particular instance. The match attribute may be used to supply a pattern identifying the portion of a document concerning which certainty is being expressed. The value of the match attribute is an XPath expression using the syntax defined in Kay (ed.) (2007). In the following example, we wish to indicate a low degree of confidence that the persName elements used throughout the whole document have been correctly applied: No target has been supplied here, and so by default the certainty expressed would therefore apply to the parent element. However, in this case the XPath supplied as the value for match returns a set of all the persName elements in the document, independent of the current context. By contrast, in the following example only the persName elements within the second div element are in question. Similarly, we may indicate that we have more confidence in the persName tagging within those div attributes which have a type value of checked: If an element in a document is matched by more than one match expression, then the most specific pattern applies. ⁷⁹ As a simple case, if both the preceding certainty elements were present in the same document, a persName occurring within a <div type="checked"> element would potentially match both pattern expressions. However because the second pattern is more specific than the former, in fact this is the only one that would apply. If multiple patterns match and have the same priority, then the first one (in document order) is applied. Only those statements of certainty which have matched in this sense are available for conditional application using the given attribute mentioned above.

When the match attribute is processed, the namespace bindings in force are those in effect at that point in the document. For example, might be used to indicate a high degree of certainty about the content of any elements taken the namespace associated with the prefix my. This namespace prefix must be associated with an appropriate namespace definition, either on the certainty element itself, or on one of its ancestor elements.

Doubts about whether the content of an element is correct may also be expressed by assigning to locus the value value. For example, if the source is hard to read and so the transcription is uncertain:

Degrees of confidence in the proper expansion of abbreviations may also be expressed, as in the following example:

The assertedValue attribute should be used to provide an alternative value for whatever aspect of the markup is in doubt: an alternative name, or the identifier of an alternative starting or ending point, as already shown, an alternative attribute value, or alternative element content, as in this example: Since attribute values have no internal substructure, the assertedValue attribute is not generally useful for specifying alternative transcriptions;it cannot for example be used if the alternative reading contains markup of any kind. More robust methods of handling uncertainties of transcription are the unclear element and the app and rdg elements described in chapter 12 Critical Apparatus. 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.

A typical case where it may be convenient to specify both target and match is that where we wish to indicate that the value of an attribute on some specific element is uncertain. In this case, the locus attribute takes the value value. For example, supposing there is only a 50 percent chance that the question was spoken by participant A: or, equivalently and without the need to define a target,

The match and target attributes together provide a powerful mechanism which can be used to indicate precision for a large number of assertions throughout an encoded document in an economical way. Some further examples follow: This encoding indicates that there is only a 0.2 certainty that the boundaries of all p elements in the document have been correctly identified.

This encoding indicates that there is only a 0.2 certainty that the boundaries of the p elements contained by the element with xml:id value a101 have been correctly identified.

This encoding indicates that there is only a 0.2 certainty that the value for the resp attribute on the given persName element is correct.

This encoding indicates that there is only a 0.2 certainty that any value for the resp attribute is correct, wherever it appears in the document.

This encoding indicates that there is only a 0.2 certainty that the value for the resp attribute of the element indicated by the pointer #dd001 is correct

This encoding indicates that there is only a 0.2 certainty that the content of any element the resp attribute of which has the value #LB is correct, wherever it appears in the document.