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Linking in DITA Topics

Direct Links

Inline links can be created DITA topics using the <xref> element. The destination of the link can be expressed directly by using the @href attribute and the target can be another topic or a specific element within the other topic, another location within the same topic, a file, or a web link. You can also create direct related links to topics, files, or websites in a DITA topic using the <related-links> element.

Indirect Links Using Keys

The destination of the link can also be expressed indirectly by using keys to create either inline links or related links (with the @keyref attribute). By using keys, you avoid creating a direct dependency between topics. This makes links easier to manage and can make it easier to reuse topics in various publications. It can also be helpful in verifying the completeness of a publication, by ensuring that a publication map provides a key definition for every key reference used in the content.

Links based on keys require two pieces:
  • Key Definition - Assigns a key to a topic so that other topics can link to it. For more information, see Defining Keys in DITA Maps.
  • Key Reference - Created in an <xref> element and specifies the key to link to.
The key reference points to a key definition, and the key definition points to a topic. Key definitions are created in maps, as an element on the <topicref> element that points to a topic. This allows you to assign a particular key to one topic in one map and to another topic in another map. When a topic that links to that key is used in each of these maps, the links work correctly in both maps.

Inserting a Link in Oxygen XML

To insert a link in Author mode, use the actions available in the Link drop-down menu from the toolbar (or the Link submenu in the contextual menu or DITA menu). You can choose between the following types of inline links:

Cross Reference
Opens the Cross Reference (xref) dialog box that allows you to insert a cross reference link to a target DITA resource at the current location within a document. The target resource can be the location of a file or a key that is already defined in your DITA map structure. Once the target resource has been selected, you can also target specific elements within that resource. Depending on the context where it is invoked, the action inserts one of the following two elements:
  • <xref> - Used to link to other topics or another location within the same topic and points to the target using the @href or @keyref attribute.
  • <fragref> - A logical reference to a fragment element within a syntax diagram and points to the target using the @href or @keyref attribute.
File Reference
Opens a dialog box that allows you to insert a link to a target non-DITA file resource at the current location within a document. The target resource can be the location of a file or a key that is already defined in your DITA map structure. It inserts an <xref> element with either an @href attribute or a @keyref attribute. If you select Location for the target, the link is expressed in an @href attribute. If you select Key for the target, keys will be used to express the link in a @keyref attribute. You can select a key from the drop-down list or click the Choose Key Reference button to use the Choose Key dialog box.
Web Link
Opens a dialog box that allows you to insert a link to a target web-related resource at the current location within a document. The target resource can be a URL or a key that is already defined in your DITA map structure. It inserts an <xref> element with either an @href attribute or a @keyref attribute. If you select URL for the target resource, the link is expressed in an @href attribute. If you select Key for the target, keys will be used to express the link in a @keyref attribute. You can select a key from the drop-down list or click the Choose Key Reference button to use the Choose Key dialog box.
Related Link to Topic
Opens the Cross Reference (xref) dialog box that allows you to insert a link to a target DITA resource in a related links section that is typically at the bottom of your topic (although this depends on the behavior of the output transformation). The target resource can be the location of a file or a key that is already defined in your DITA map structure. Once the target resource has been selected, you can also target specific elements within that resource. If a related links section does not already exist, this action creates one. Specifically, it inserts a <link> element inside a related-links element.
Note:
Related Link to File
Opens a dialog box that allows you to insert a link to a target non-DITA file resource in a related links section that is typically at the bottom of your topic (although this depends on the behavior of the output transformation). The target resource can be the location of a file or a key that is already defined in your DITA map structure. If a related links section does not already exist, this action creates one. Specifically, it inserts a <link> element inside a related-links element. If you select Location for the target, the link is expressed in an @href attribute. If you select Key for the target, keys will be used to express the link in a @keyref attribute. You can select a key from the drop-down list or click the Choose Key Reference button to use the Choose Key dialog box.
Related Link to Web Page
Opens the Web Link dialog box that allows you to insert a link to a target web-related resource in a related links section that is typically at the bottom of your topic (although this depends on the behavior of the output transformation). The target resource can be a URL or a key that is already defined in your DITA map structure. If a related links section does not already exist, this action creates one. Specifically, it inserts a <link> element inside a related-links element. If you select URL for the target resource, the link is expressed in an @href attribute. If you select Key for the target, keys will be used to express the link in a @keyref attribute. You can select a key from the drop-down list or click the Choose Key Reference button to use the Choose Key dialog box.

Cross Reference (xref) Dialog Box

The Cross Reference (xref) dialog box is displayed when you insert a Cross Reference or Related Link to Topic (from the Link drop-down menu). It allows you to insert a link to a target resource at the current location within a document (for a Cross Reference link) or in a related links section (for a Related Link to Topic). The target resource can be the location of a file or a key that is already defined in your DITA map structure. Once the target resource has been selected, you can also target specific elements within that resource.

Figure 1. Cross Reference (xref) Dialog Box
Figure 2. Cross Reference (xref) Dialog Box
This dialog box includes the following sections and fields:
Choose the Target Resource Section
Once you click Insert or Insert and close, the configured cross reference is inserted into your document.
Tip:
You can easily insert multiple cross references by keeping the dialog box opened, using the Insert button.

Using Copy/Paste or Drag/Drop Actions to Insert a Cross Reference

Oxygen XML also includes support for inserting cross reference links with simple copy/paste or drag/drop actions (additionally, you can insert them using the Paste as Link or Paste as Link (keyref) actions found in the Paste Special submenu from the contextual menu). The copied/dragged content must be an entire DITA XML element with an @id attribute or a <topicref>. Also, the location in the document where you paste or drop the link must be valid, although as long as the Smart paste and drag and drop option is selected in the Schema-Aware preferences page, if you try to paste it in an invalid location, Oxygen XML will attempt to place it in a valid location, and may prompt you with one or more choices for where to place it.

When the link is inserted, Oxygen XML automatically tries to populate certain attributes based on detected values. The @format, @scope, and @type attributes are populated if their corresponding options are selected in the Inserting Links section of the DITA Topics preferences page. Even if their corresponding options are not selected, the @format and @scope attributes are populated if their detected values are different than the default values.

Note:
For the sake of performance, the @type attribute is never automatically computed in the following cases:
Typically, cross reference links are inserted with an @href attribute, but it is also possible to insert them with a @keyref attribute using the Paste as Link (keyref) contextual menu action or copy/paste or drag/drop actions. For the latter method, follow these steps :
  1. In the DITA Maps Manager view, make sure that the Context combo box points to the correct map that stores the keys.
  2. Make sure the topic that contains the content you want to reference has a key assigned to it. To assign a key, right-click the topic with its parent map opened in the DITA Maps Manager, select Edit Properties, and enter a value in the Keys field.
  3. Copy an entire DITA element that has an ID attribute assigned to it from a topic with an assigned key, or a <topicref> from a DITA map.
  4. Place the cursor at a location, where you want to insert the link.
  5. Select the Paste as Link (keyref) action from the Paste Special submenu from the contextual menu.