  Tabular visualization techniques integrate visual representations with
tabular data to avoid additional cognitive load caused by splitting users'
attention. However, most of the existing studies focus on simple flat tables
instead of hierarchical tables, whose complex structure limits the
expressiveness of visualization results and affects users' efficiency in
visualization construction. We present HiTailor, a technique for presenting and
exploring hierarchical tables. HiTailor constructs an abstract model, which
defines row/column headings as biclustering and hierarchical structures. Based
on our abstract model, we identify three pairs of operators, Swap/Transpose,
ToStacked/ToLinear, Fold/Unfold, for transformations of hierarchical tables to
support users' comprehensive explorations. After transformation, users can
specify a cell or block of interest in hierarchical tables as a TableUnit for
visualization, and HiTailor recommends other related TableUnits according to
the abstract model using different mechanisms. We demonstrate the usability of
the HiTailor system through a comparative study and a case study with domain
experts, showing that HiTailor can present and explore hierarchical tables from
different viewpoints. HiTailor is available at
https://github.com/bitvis2021/HiTailor.
