colspec

Specifies a column, a vertical portion of a table. The default values come from the tgroup or thead starting the current (enclosing) group. Each colspec is for a single column in left-to-right order, so it properly has a column number, colnum, implicitly in order starting from 1, and an optional column name (colname) by which it is known when referenced by any entry . Any references from entrys within the thead to colname, namest, or nameend refer to values defined by the set of colspecs in the containing tgroup. colspecs from the containing tgroup apply to thead and tbody.
The number of columns should be determined by the cols attribute on the tgroup element, not by the number of colspecs actually defined. If the number in cols is larger than the number of colspecs, then additional colspecs of colwidth "1*" should be inferred. colspecs can be numbered or unnumbered, and if numbered should be increasing in sequential order starting with 1 at the left. Unnumbered colspecs are interpreted as being numbered incrementally (one more than the previous column number), with the first colspec starting at 1. It is left up to the implementation how to handle any mismatch in colspec numbering, or a number of colspecs greater than cols. It is recommended that an authoring or editing implementation or any implementation that verifies the compliance of the table markup to this Memorandum offer the option of producing a warning message when it encounters such markup. It is an error for an authoring or editing implementation to produce a table with such conflicting markup.
The char and charoff attributes are allowed on colspec as well as on entry. While an implementation should accept these attributes on either of these elements upon input, it may produce logically equivalent output that nevertheless differs with respect to these attributes and still be considered in compliance with the semantics of this Memorandum. If a table contains one or more entrys with values of either char or charoff that differ from the value for the same attribute on a colspec that logically contains the entry(s), it is left up to the implementation how this should be handled (i.e., the interpretation of such markup is beyond the scope of this model). It is recommended that an authoring or editing implementation or any implementation that verifies the compliance of the table markup to this Memorandum offer the option of producing a warning message when it encounters such markup. It is an error for an authoring or editing implementation to produce a table with such conflicting markup.