Pedantic note

In the paragraph in 2.1.2 discussed here [1], there are three "if and only
if" statements. Two of these are when "a SHACL process MUST recognize a
resource X in the shapes graph." I would argue that the iff in these cases
should be demoted to just "if". MUST, being a compulsion on the user, would
be invoked as a consequent but not as an antecedent. Similarly, the third
iff statement could be weakened to a form "..a resource R in the data graph
is said to be an instance of the resource X *when* the data graph
contains.."

[1]
http://lists.w3.org/Archives/Public/public-data-shapes-wg/2016Jan/0104.html