!2 The Sub Page widget in an alias.
Sometimes we want to create an alias to a subpage link as follows: !-[[click here][^SubPage]]-!.

|Page creator.|
|Page name.|Page contents.|Page attributes.|valid?|
|!-SuperPage-!|!-[[tag][^SubPage]]-!||true|

|Response Requester.|
|uri|valid?|contents?|
|!-SuperPage-!|true||

The widget should translate into a ? link of the form:
 * ''tag<a title="create page" href="!-SuperPage.SubPage-!?edit&nonExistent=true">[?]</a>''
|Response Examiner.|
|type  |pattern|matches?|value|
|contents|tag<a title="create page" href="!-SuperPage.SubPage-!\?edit&nonExistent=true">\[\?\]</a>|true||

If the sub page is already present, then the widget should translate into a normal link.

|Page creator.|
|Page name.|Page contents.|Page attributes.|valid?|
|!-SuperPage.SubPage-!|nothing||true|

|Response Requester.|
|uri|valid?|contents?|
|!-SuperPage-!|true||

|Response Examiner.|
|type  |pattern|matches?|value|
|contents|<a href="!-SuperPage.SubPage-!">tag</a>|true||
