Added global settlement for dependent MPAs

bsip-0017.md

@@ -250,6 +250,30 @@ event on an asset and the revival of that same asset. The parameter will be
 modifiable by the committee and defaults to 4 weeks (28 days). See discussion
 below.
 
+### Dependent MPAs
+
+If at the time of global settlement an MPA exists that is backed by the settled
+asset, that dependent MPA is also settled.
+
+Additionally, it will be forbidden to create assets backed by bitAssets that
+have a settlement_price.
+
+The reason for this is that after global settlement the settled asset is no
+longer pegged to its "real" counterpart. For example, suppose that an asset
+bitGOLD_USD exists that is supposed to represent the value of an amount of gold
+and is backed by an amount of bitUSD (which is supposed to be pegged to the
+US-Dollar). After bitUSD has suffered a black swan, bitUSD is no longer pegged
+to USD. Instead, bitUSD represents a fixed amount of BTS, defined by the
+settlement_price.
+
+Supposedly, the price feed for bitGOLD_USD will continue to follow the gold
+price in terms of US-Dollars, which will quickly deviate from the actual worth
+of bitGOLD_USD, which is really defined by the BTS price at that time. This will
+lead to confusion and anger among market participants. It is therefore
+reasonable to put bitGOLD_USD into the same state of limbo as the backing USD.
+
+This change requires further discussion.
+
 # Discussion
 
 ## minimum_time_before_asset_revival