The href attribute in a topic references

A topic reference (topicref) in a ditamap references the topic (or other resource) to be included in the output publication through the href attribute. The value of the href attribute must conform to the standard URI format.

Topic reference (topicref) elements usually reference a DITA topic, but can also reference external resources such as Web sites. The resources being referenced in topicref element are specified in the href attribute.

A URI, or Uniform Resource Indicator, is a standard for referencing resources on the Internet. The similar term URL, or Uniform Resource Locator, means a specific type of URI where the location and the means of retrieving the resource are both incorporated in the address. For example, the URL nominates the address of the resource and the protocol to use to retrieve it (in this case, http). In general, however, most people use the terms interchangeably!

Files on a file server or network drive on a local network can be referenced using the URI convention. Most DITA authoring tools will let you browse for the resource you want to reference, and then format the address in the correct UNC format. For example, the address of a file on a network server must be prefixed with the protocol smb://.

You must use (forward) slash characters for path separators. Do not use backslashes. Such file references are URIs in DITA, not file paths. The backslash is an illegal character in URIs. When referencing resources on a network server, prefix the UNC path with smb://.

You cannot use an ampersand (&) character in an href attribute. If the URL being referenced contains an ampersand character, the & character escape should be used to indicate that character.