In addition to the common document interface, some aspects of the help writers are similar or are made similar with an initial view to having a single source for all types of help documentation requirements. While in the later stages of their development the design has veered away from the initial paradigm in order to implement features unique to a particular type of help format, they are still considerably single-source-implementable. The commonality of design in their structure and operation are documented, which is accessible in the Common Aspects link.