Database extractor

Wandora has a feature to import any relational database. Information in the database will be converted into topic map format and then imported. This page describes how the conversion is done from relational database format into topic map format.

Basic idea is that each row of each table is converted to a topic, there are some exceptions to this rule. Since primary key(s) identify the row inside the table, it is natural to use the pimary keys with the table name as the subject identifier of the topic.

Values of each normal column, that is column that is not a reference to some other (or same) table, is converted to either an occurrence or a new topic which is then associated with the topic representing the row. Creating topics for column values is natural when the value is shared by many rows, for example when the value represents a year. Creating occurrences is better suited for situations where most or all rows have unique values and creating separate topics would only make the topic map more complex without offering any additional linkage between topics.

Columns that reference some other column in another or same table are converted to associations. This is the natural thing to do as the referenced row is also a topic and the reference associates these two topics (rows). Current version of Wandora does not support database schemas where several columns together reference another row.