Count of previous statements that are referenced from replacesStatement and NOT in the dataset

[siwhitehouse]

There may be the following scenario:

Statement A [ MISSING ]
Statement B Replaces Statement A
Statement C Replaces Statement A, B

@odscjames raised the question of whether that data set is valid - should Statement C list A as well as B?

The docs are not clear on what the expected use of replacesStatement is in this case. @kd-ods suggested that we should require that Statement C lists both A and B, which would support the streaming API use case.

In relation to this particular statistical count, @kd-ods thinks the count should be 1. Naming this count 'Replaced statements missing from the dataset' would make that clearer.

[siwhitehouse]

This was copied across from Open Data Sevices (internal) helpdesk issue http://bods.opendataservices.coop/redmine/issues/321

[kd-ods]

Various problems with replacesStatements as a way of capturing change over time led to it being retired after BODS version 0.4. This underspecification was just one of the problems.

It is imo not worth properly specifying a retired field in order to validate it.