#### 36.5.1 Understanding how the ColGroup property works

When you designate a header cell as a ColGroup cell, the effect of that property on the table depends on which accessibility method you have specified:

scope | (via AccessMethod=Scope or via ScopeColGroup=Yes)
id/headers | (via AccessMethod=IDheaders or via ColGroupIDs=Yes)

Using the scope method automatically specifies ColGroupElements=Yes; the ColGroup cell starts a new <colgroup> element; and the ColGroup cell’s information applies to all cells subsumed by that element.

ColGroupElements=Yes is a necessary condition for scope="colgroup", but not for id/headers="groupN"; for the latter, the ColGroupElements value does not affect which cells are marked id/headers="groupN".

ColGroupIDs=Yes is a necessary condition for id/headers="groupN", but not for scope="colgroup"; for the latter, the ColGroupIDs value does not affect which cells are subsumed under scope="colgroup".

Table 36-3 summarizes the effects of the ColGroup property when combined with these settings.

Table 36-3 ColGroup property effects

* Set via CellScope PI marker or [HTMLParaStyles]fmt=Scope, [HtmlStyleCellScope]fmt=colgroup
Setting |
    ColGroupElements
| Yes | No
    ColGroupIDs
| Yes | No | Yes | No
    scope="colgroup" *
| Yes | No | Yes | No | Yes | No | Yes | No
Effect | starts new <colgroup> | Yes | Yes | Yes | Yes | No | No | No | No
    id/headers="groupN"
| Yes | Yes | No | No | Yes | Yes | No | No
scope attribute applied | Yes | No | Yes | No | No | No | No | No

If ColGroupElements=Yes, each ColGroup cell starts a new <colgroup> element. If the ColGroup cell contains a CellScope PI marker (or the [HTMLParaStyles]/[StyleCellScope] equivalent) that sets the scope="colgroup" attribute, the ColGroup property works in concert with the scope attribute to apply the ColGroup header to all cells subsumed by its <colgroup>. The scope attribute is in effect only within the same <colgroup> section as the ColGroup cell. See §36.2 Using the scope method to identify table cells.

If ColGroupIDs=Yes, each ColGroup cell gets an id="groupN" attribute; cells below the header cell and to the right of the header-cell column, across to the next ColGroup header cell or to the edge of the table (see Figure 36-1), each get a matching headers="groupN" attribute. If ColGroupElements=Yes, these are the cells subsumed by the <colgroup> element. See §36.3.3 Grouping header cells for identification.

Previous Topic: 36.5 Using ColGroup and RowGroup cells

Next Topic: 36.5.2 Understanding how the RowGroup property works

Parent Topic: 36.5 Using ColGroup and RowGroup cells

Sibling Topics:

36.5.2 Understanding how the RowGroup property works

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