(topic learningBase+learningInteractionBase-d+learningInteractionBase2) The learningBase topic type is not used to deliver any actual learning content, but instead provides a set of common elements for use in the other more specific learning content types: learningOverview,learningContent, learningSummary, learningAssessment, and learningPlan. The <learningBasebody> element is the main body-level element in a learningBase topic. The learningBase topic provides a set of base elements for use in the other specialized learning types. It is not generally intended for creating actual content. As such, each of the body sections in learningBase are optional. The <lcIntro> provides a detailed introduction and description of the content to be delivered, in cases where the <shortdesc> is not adequate to fully describe the content. It may also include instructor notes. The <lcObjectives> lists or describes the learning goals. The <lcObjectivesStem> provides a leading sentence to introduce a list of learning objectives. The <lcObjectivesGroup> contains a list of one or more learning objectives. The <lcObjective> describes a single learning objective. The <lcAudience> describes characteristics of the learners who take the instruction. The <lcDuration> provides an estimated duration for the learning activity. The <lcTime> specifies the time expected to complete an activity. The <lcPrereqs> describes the knowledge, experience, or other prerequisites needed to complete the content. The <lcSummary> provides a textual summary that describes the main learning goals and lessons learned. The <lcNextSteps> suggests next steps to reinforce the knowledge learned. The <lcReview> provides a review of the main points. The <lcResources> provides a list of related resources and information about them, such as related articles or samples on the web. The <lcChallenge> refers to what it is that you want the student to practice. For example, if you're studying network diagrams, and challenge might be "see if you can put this network into its proper sequence" or "see if you understand this network flow". The <lcInstruction> describes the specifics of a learning activity. The <lcInteraction> is a wrapper element for all the interactions of the assessment. The interactions themselves are based on a basic set of assessment types implemented as a DITA domain specialization.