* @brief A small class collecting the different BlockIndices involved in
* global, multilevel and local computations.
*
- * In addition to grouping all the block indices into a single
- * instance, this class also provides functions to fill them
- * automatically.
+ * Once a DoFHandler has been initialized with an FESystem, a data
+ * object of type BlockInfo (accessed by DoFHandler::block_info() ) is
+ * filled, which reflects the block structure of the degrees of
+ * freedom.
+ *
+ * BlockInfo consists of deveral BlockIndices objects. The member
+ * global() reflects the block structure of the system on the active
+ * cell level, usually referred to as the global system. As soon as
+ * DoFHandler::distribute_dofs() has been called, the function
+ * BlockIndices::block_size() in global() will return the correct
+ * sizes of each block. After DoFRenumbering::block_wise(),
+ * BlockIndices::block_start() will return the start index for each of
+ * the blocks.
+ *
+ * When an MGDoFHandler is used, the same structure is automatically
+ * generated for each level. The level blocks can be accessed through
+ * level().
+ *
+ * Finally, there are local() BlockIndices, which describe the block
+ * structure on a single cell. This is used for instance by
+ * MeshWorker::Assembler::MatrixLocalBlocksToGlobalBlocks. The local
+ * indices are not filled automatically, since they change the
+ * behavior of the MeshWorker::Assembler classes relying on
+ * BlockInfo. They must be initialized by hand through initialize_local().
*
* @todo Extend the functions local() and renumber() to the concept to
* hpDoFHandler.
* structure of a PDE system in linear algebra, in particular allowing
* for modular solvers for problems with multiple solution components.
* How to implement this is described in more detail in the
- * @ref vector_valued report and the tutorial programs referenced
+ * documentation of FESystem, the
+ * @ref vector_valued module and the tutorial programs referenced
* therein.
*
* Originally, this concept was intermixed with the idea of the vector