Modifying occurrences
Occurrence is a solid text block associated to the topic. Occurrence has type and scope. Type is a topic that describes the occurrence. Topic's description is an example of occurrence type. Scope is also a topic describing the occurrence. Usually scope specifies the language of the occurrence. Type and scope are orthogonal. Topic map standard supports URL occurrences addition to text occurrences. However, Wandora does not support URL occurrences as it is possible to set URL's external representation, the string representing URL, as the occurrence.
Occurrence is added to a topic by selecting Add occurrence.... Occurrences employ schema similar to association schema. Occurrence schema specifies what kind of occurrences can be added to a topic i.e. the types of allowed occurrences. Read more about the schema here. As schema creation is rather difficult, also schemaless occurrence addition is allowed.
Occurrence editor doesn't allow user to specify occurrence scopes freely. User must always choose scope from Wandora's language topics. This is usually enough as scopes should not vary too much. To add occurrence of non-listed scope, add your scope topic as an instance to Wandora language. Read more here.
More advanced occurrence operations are found in Topics > occurrence menu of topic tables:
- Delete occurrences with type removes occurrences of given type from context topics.
- Delete all occurrences removes all occurrences from context topics.
- Regex replace modifies occurrence text with given regular expression. This can be used to perform rather complicated search and replace operations for example.
Note: For historical reasons Wandora calls occurrences also as Text datas.
