First of all, we should highly take into our consideration that no single type of syllabus is appropriate for all teaching settings. This is because of the fact that the conditions and needs of every setting are so idiosyncratic and characteristic. Generally, tasks can be selected based on the needs analysis of learners. As a result, they can satisfy their demands. A task-based structural syllabus serves as an appropriate unit for specifying learners’ needs and accordingly for designing specific purposes courses. It maintains using tasks and activities to support learners to employ the language communicatively in order to achieve a purpose. It points out that speaking a language is a skill best perfected throughout (interaction and practice). This kind of syllabus makes the focus on the structural form of language being learnt. It proceeds from simple grammatical structure to more difficult grammatical one. Moreover, functional ability arises from structural knowledge.
I am not completely clear about your question. Are you talking about the structure of the syllabus document itself, or about the instructional design of the course?
A task-based instructional design should use tasks to practice the skills taught in class to allow the student to move from the novice to mastery level. It should NOT be used for the other reasons, such as to reduce the workload of the teacher.
If you question primarily deals with task based syllabus design,, i may refer you to Ellis (2003) Task-based language learning and teaching (esp. Chapter 7).
I hope it will be helpful.
The book also covers and illuminates the areas of task-based course design, methodology, ....
I don't have a specific answer, but if you read my publication ()coauthored paper), you'll definitely find an answer to your question:
Abdallah, M. M. S. & Mansour, M. M. (2015). Virtual Task-Based Situated Language-Learning with Second Life: Developing EFL Pragmatic Writing and Technological Self-Efficacy. Arab World English Journal (AWEJ), Special Issue on CALL No.2, July, 2015, pp.150-182. Available at: http://awej.org/images/AllIssues/Specialissues/CALLjuly2015/11.pdf
Article Virtual Task-Based Situated Language-Learning with Second Li...