Help:属性约束专题/格式约束
 | This is the documentation page for a particular constraint type. See Help:Property constraints portal for a general overview of property constraints. |
format constraint (Q21502404) specifies that values for a property should conform to a certain pattern.
例如，GNIS Feature ID (P590)的值應始終為最多八位數的數字，不帶前導零：[1-9][0-9]{0,7}。
The pattern is a regular expression, but the flavor varies: KrBot, which creates the database reports, uses PCRE; the WikibaseQualityConstraints extension, which powers the live constraint checks and Special:ConstraintReport, uses PCRE since August 2021 (having previously used java.util.regex); OpenRefine uses java.util.regex; other implementations may use something else to check regular expressions. The flavors are mostly, but not entirely compatible; for maximum compatibility with different constraint engines, it’s recommended to stick to the common subset of the flavors.
如果未指定constraint scope (P4680)，則會在任何位置檢查此約束。
可能的配置
有幾種方法可以解決違反此約束的問題：
- The most likely case is that the value is malformed in some way. Often the fix is straightforward: add a missing prefix or remove one that should be implicit, add punctuation (e. g. add hyphens to an ISBN), fix capitalization, etc.
- It’s possible that the value is correct, but does not belong to this property, and that it should be moved to a statement for a different property (e. g. ISBN-13 (P212) to ISBN-10 (P957)).
- It’s possible that the identifier has expanded its range and the regex needs to be adapted (e.g. an identifier now uses up to 15 digits and not 10 as when it was first defined).
- It’s possible that the item is a rare, but legitimate exception to the constraint, and nothing should be done.
参数
This constraint has one mandatory and one optional parameter:
- format as a regular expression (P1793)
- Contains the format / pattern. Must contain exactly one value (no value Help or unknown value Help is not permitted), which must be a valid regular expression. Note that, at least for WikibaseQualityConstraints, the pattern should not be escaped (e.g.
/should not be escaped as\/). - syntax clarification (P2916)
- Contains a human-readable description of the pattern. Can be specified several times in different languages.
 | 警告： format as a regular expression (P1793) is also often used as a top-level statement of a property, but this usage does not constitute a constraint: to specify a format constraint, a property constraint (P2302)format constraint (Q21502404) statement with format as a regular expression (P1793) qualifier must be used. |
Examples
Example 1
Values for image (P18) should end with certain file extension like .jpg or .png.
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Example 2
Using syntax clarification (P2916) parameter for explaining the regular expression in human-readable text. For example, value of IPA transcription (P898) doesn't contain : (colon) or ' (apostrophe). Correct character is ː (length) or ˈ (stress). This regular expression is difficult to understand without explanation.
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Template
When the constraint is set to the property, the following template is automatically displayed in the property talk page. The template is created by Module:Constraints using Template:Constraint, invoked from Template:Property documentation. Translations are defined at Module:i18n/constraints.
(?i).+\.(jpg|jpeg|jpe|png|svg|tif|tiff|gif|xcf|pdf|djvu|webp)|”: value must be formatted using this pattern (PCRE syntax). (Help)List of violations of this constraint: Database reports/Constraint violations/P18#Format, SPARQL
Lists
Lists of properties which are set format constraint.
- Category:Properties with format constraints
- SPARQL query - click the execute button
at the linked page to see the query result.
