The UIMA Ruta language is an imperative rule language extended with scripting elements. A rule defines a
pattern of annotations with additional conditions. If this pattern applies, then the actions of the rule are performed
on the matched annotations. A rule is composed of a sequence of rule elements and a rule element essentially consists of four parts:
A matching condition, an optional quantifier, a list of conditions and a list of actions.
The matching condition is typically a type of an annotation by which the rule element matches on the covered text of one of those annotations.
The quantifier specifies, whether it is necessary that the rule element successfully matches and how often the rule element may match.
The list of conditions specifies additional constraints that the matched text or annotations need to fulfill. The list of actions defines
the consequences of the rule and often creates new annotations or modifies existing annotations.
The following example rule consists of three rule elements. The first one (ANY...) matches on every token, which has a covered text that occurs in a word lists, named MonthsList.
The second rule element (PERIOD?) is optional and does not need to be fulfilled, which is indicated by the quantifier ?. The last rule element (NUM...) matches
on numbers that fulfill the regular expression REGEXP(".{2,4}" and are therefore at least two characters to a maximum of four characters long.
If this rule successfully matches on a text passage, then its three actions are executed: An annotation of the type Month is created for the first rule element,
an annotation of the type Year is created for the last rule element and an annotation of the type Date
is created for the span of all three rule elements. If the word list contains the correct entries, then this rule matches on strings like
Dec. 2004, July 85 or 11.2008 and creates the corresponding annotations.
ANY{INLIST(MonthsList) -> MARK(Month), MARK(Date,1,3)}
PERIOD? NUM{REGEXP(".{2,4}") -> MARK(Year)};
Here is a short overview of additional features of the rule language:
- Expressions and variables
- Import and execution of external components
- Flexible matching with filtering
- Modularization in different files or blocks
- Control structures, e.g., for windowing
- Score-based extraction
- Modification
- Html support
- Dictionaries
- Extensible language definition
Apache UIMA Ruta (Rule-based Text Annotation)