What is a content strategy? A content strategy reveals who the end users are, the goals they are pursuing and what tasks they must do to reach the goals. The content strategy explicitly describes what type of information end users need to do the tasks, which gives us the content to include and not include in a manual and how to organize it to make content searchable. A content strategy shall answer a number of questions (for example, open the document via link "information design questions" On http://www.sesam-info.net/planning.htm). The answers are sometimes referred to as the information model.

The content strategy shall also deal with areas such as metadata, reuse strategy, creation and release processes, publishing mechanisms, content ownership and responsibility, tools etc.

Let us elaborate two types of content creation organizations within the technical communication domain: Explicit and implicit organizations.  In the implicit organization there are no content strategy written down. Each member (technical writer, SME etc) has their own view on what content they believe end users need. In the best of worlds these views are aligned without the members having discussed it. In other implicit organizations an information designer has taken the role to plan and design the content (together with the team or not). But the strategy and principle that the information designer is following may not be communicated or understood by the technical writers or SMEs. So the information designer has to be consulted every time a new manual is developed or a macro content change is proposed in an existing manual. In explicit organizations the strategy and principles are written down and communicated.

If a help ID should provide a list of related topics, those topics are shown as separate <relcell> entries in the corresponding <relrow>:

<relrow id=”h4444444″>

This encoding approach takes care of the DITA source side of the context-sensitive help. You’ll need to build a DITA Open Toolkit plugin that processes the relationship table and creates the appropriate mapping files.

Keys provide a way for authors to create addresses to resources through the use of a named identifier rather thanto a specific URI pointer. In other words, I can create an easy-to-remember key, like “ms-word-functions” that actually resolves to a URL “http://support.microsoft.com/kb/211982” and link to this URL using the key name in my DITA topic.

Any time a topic makes use of a key reference, that topic is explicitly binding itself to a map (or many maps), meaning that a topic is no longer a unit of information that is completely independent of any particular context in which it is assembled into. You could make the argument that any reference defined in a topic to an external resource (e.g., an image or a cross-reference to another topic) by definition creates a dependency on that topic. And arguably, the referenced (the endpoint) resource is unaware of the object that is referencing it, regardless of whether it's a topic reference or a cross-reference. But there is an additional dependency in the case of keys: Any map that references a topic with a key reference must define the key. So in a sense, not only does the map (or an ancestor map) need to know about the topic, it needs to discover what the topic is about, specifically related to any key references it points to. Consequently, somewhere along the line, at least one map must define the keys used by a topic.  Did you get all that?  Imagine what your XML authoring tools, CMS systems, and rendering platforms will need to do to manage this.

there are potential downsides too.  Keys and key references add another layer of complexity to planning the authoring, deployment and management of DITA content.  

is not about less content, it is about the reader spending less time on the content.

This is where constraints in the upcoming DITA 1.2 spec comes to the rescue, as it provides a means to specialize without specialization, not by creating new elements, but by constraining your usage of DITA elements to those you actually use. This results in a writing team needing less than the full standard, usefully constraining what tags a writer can use in order have them better focus on the job that they are supposed to do. His take on using them was to start with the most constrained condition, and then loosen the constraints as required as needs evolve.

In a topic-oriented architecture such as DITA, content is authored in small, independent units that are assembled to provide help systems, books, courses, and other deliverables. Each unit of information answers a single question for a specific purpose. That is, each topic has specific, independent subject matter

Because each topic has a specific meaning, DITA topics are tailor-made for semantic processing. However, current semantic processors can't read the text of a topic to find out what it means. What's missing is a formal declaration of the topic's subject matter that a semantic processor can understand

Simple Knowledge Organization System (SKOS) provides a standard for indicating the subject matter of content. SKOS lets you define the subjects for a particular subject matter area (organizing these subjects as a taxonomy if desired) and then classify each piece of content to indicate its subject. For instance, using SKOS, you could define configuration and security as subjects, and classify the three example topics that relate to those subjects so that users could browse the subjects to find the content regardless of whether the words "configuration" or "security" actually appear in the text.