The <keyword> element identifies a keyword or token, such as a single value from an enumerated list, the name of a command or parameter, or a lookup key for a message (contrast with term). Attributes that support both filtering and flagging include platform, product, audience, and otherprops. Attribute rev only lets you flag information that matches a run-time parameter. Attribute importance currently provides output effects only for steps (where only the values "optional" and "required" are supported). ID attributes (%id-atts;) is a parameter entity declaration in the topic DTD that includes attributes that enable the naming and referencing of elements in a DITA topic: id and conref. Universal attributes is a parameter entity declaration in the topic DTD that includes all of the attributes in the select-atts and id-atts attribute groups. Universal attributes is a parameter entity declaration in the topic DTD that includes all of the attributes in the select-atts and id-atts attribute groups. The %topicref-atts; parameter entity represents a group of attributes used in numerous map elements: map, topicref, relcolspec, relcell, topichead, and topicgroup. The set is similar to those documented in topicref-atts-no-toc but includes the toc attribute. The %topicref-atts-no-toc; parameter entity represents the set of attributes used in the reltable map element. The set is similar to those documented in topicref-atts but for <reltable> the toc attribute defaults to no. For the other elements that use the %topicref-atts; group declaration, the toc attribute doesn't have a default; they can inherit their toc value from the nearest container, otherwise it functions upon output as if set to yes. The <map> element is used to define a map which describes the relationships among a set of DITA topics. Maps consist of references to topics organized into hierarchies and tables. Maps provide a way to express these relationships in a single common format that can be used for different outputs. The <navref> element references a map file from within a map file. The reference is resolved at runtime for Eclipse navigation, typically to pull together the navigation for multiple components into a product navigation. The <topicref> element designates a topic (such as a concept, task, or reference) as a link in a DITA map. A <topicref> can contain other<topicref> elements, allowing you to express navigation or table-of-contents hierarchies, as well as implying relationships between the containing <topicref> and its children. You can set the collection-type of a container <topicref> to determine how its children are related to each other. Relationships end up expressed as links in the output (with each participant in a relationship having links to the other participants). The relationship table (<reltable>) defines relationships between topics, based on the familiar table model of rows (<relrow>), columns (<relheader>), and cells (<relcell>). The <relcell> elements can contain <topicref> elements, which are then related to other <topicref> elements in the same row (although not necessarily in the same cell). By default, the contents of a <reltable> element are not output for navigation or TOC purposes, and are used only to define relationships that can be expressed as topic-to-topic links. The <relheader> element is a row of column definitions (<relcolspec> elements) in a relationship table. Each table can have only one set of column definitions. A column definition in the relationship table. You can use <relcolspec> column definitions to set defaults for the attributes of <topicref> elements in the column. For example, you can set type="concept" to treat all untyped <topicref> elements in the column as concepts. A <relrow> is a row in the relationship table. This creates a relationship between the cells in the row, which will end up expressed as links among the <topicref> elements in the cells. A <relcell> element is a cell in the relationship table. The <topicref> elements it contains will be related to topicrefs in other cells of the same row. By default, topicrefs in the same cell are not related to each other, unless you change the relcell's collection-type attribute to indicate that they are related. The <anchor> element is used for runtime integration of navigation. It provides an integration point that another map can point to in order to insert its navigation into the current navigation tree. It is currently supported by Eclipse output only. The <topicmeta> element defines the metadata that applies to a topic and the topic's children. When creating links, it can also be used to override the title and short description of the topic. In addition, it can insert index entries through the <keywords> element. The <linktext> element provides the literal label or line of text for a link. In most cases, the text of a link can be resolved during processing by cross reference with the target resource. Use the <linktext> element only when the target cannot be reached, such as when it is a peer or external link. When your DITA topic is transformed to XHTML, the <searchtitle> element is used to create a title element at the top of the resulting HTML file. This title is normally used in search result summaries by some search engines, such as that in Eclipse (http://eclipse.org); if not set, the XHTML's title element defaults to the source topic's title content (which may not be as well optimized for search summaries) The short description (<shortdesc>) element occurs between the topic title and the topic body, as the initial paragraph-like content of a topic. The short description, which represents the purpose or theme of the topic, is also intended to be used as a link preview and for searching. The class attribute supports specialization. Its predefined values help the output transforms work correctly with ranges of related content.