#### 16.6.1 Understanding related-topic links

Related-topic links you can produce with DITA2Go come in two flavors:

- associative link (ALink)
- keyword link (KLink).

Each consists of a jump from one topic to a list of links to other topics. The listed links are members of a set of links that share a common identifier, or link keyword. KLink keywords are actually index entries, while ALink keywords are subject terms. ALink keywords are not ordinarily visible to users, except in OmniHelp (see §19.8 Providing related-topic links in OmniHelp).

Link keywords

ALink and KLink keywords are case sensitive. Each ALink keyword must consist of a single alphanumeric term. Punctuation is not allowed; however, spaces are allowed in ALink keywords in some Help systems.

Related-topic jumps

You can generate ALinks from DITA related-links and reltables; or, you can insert ALinks in DITA XML with ALink PI markers. Use one or the other method; do not use both.

Bullet-proof links

Why use ALinks and KLinks if your document already includes cross references, See also lists, and other hypertext links? Unlike other links, an ALink or KLink jump can go (via the list of links) to multiple target topics, yet does not require the presence of any topic. Therefore, you can do the following without disturbing related-topic links:

Add a topic: | Existing ALink and KLink jumps automatically pick up any relevant link keywords in the new topic.
Remove a topic: | If no link keywords exist in the remaining topics for a given ALink or KLink jump, instead of triggering an error message, the jump does nothing.

Run-time activation

ALinks and KLinks are especially useful if you expect to merge Help projects (see §16.11 Setting up a dynamic modular Help system), for the following reasons:

- If other Help projects are merged with the main project at run time, and topics in the merged projects contain KLink or ALink keywords that appear in the main project, links to those topics are included in the relevant ALink and KLink lists in the main project.
- If a section (or a whole subproject) is not found at run time because it was not installed, any ALink or KLink references to topics in that section quietly disappear from the main project, whereas regular links would yield error messages.

KLinks access merged topics

If you merge your Help project with another Help project built by someone else, possibly using other tools, KLinks can provide the only way to add links to topics in the other project, assuming the other project has a thorough index.

Previous Topic: 16.6 Providing related-topic links for Help systems

Next Topic: 16.6.2 Understanding how ALinks work

Parent Topic: 16.6 Providing related-topic links for Help systems

Sibling Topics:

16.6.2 Understanding how ALinks work

16.6.3 Understanding how KLinks work

16.6.4 Adding related-topic link keywords in DITA XML

16.6.5 Adding ALink and KLink jumps in DITA XML

16.6.6 Creating target-and-jump ALinks for HTML-based Help

16.6.7 Specifying ALink and KLink list-link destinations

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