Merge pull request #54 from bitshares/bsip30

Add BSIP 30: Always Allow Increasing Collateral Ratio If Debt Not Increased

README.md

@@ -37,3 +37,4 @@ Number             | Title                                                    |
 [27](bsip-0027.md) | Asset Issuer Reclaim Fee Pool Funds                          | Abit More | Protocol | Accepted
 [28](bsip-0028.md) | Worker Proposal Improvements                                 | Bill Butler | Protocol | Draft
 [29](bsip-0029.md) | Asset issue change to require owner authority                | Fabian Schuh | Protocol | Draft
+[30](bsip-0030.md) | Always Allow Increasing Collateral Ratio If Debt Not Increased | Abit More | Protocol | Draft

bsip-0030.md

@@ -0,0 +1,71 @@
+    BSIP: 0030
+    Title: Always Allow Increasing Collateral Ratio If Debt Not Increased
+    Author: Abit More <https://github.com/abitmore>
+    Status: Draft
+    Type: Protocol
+    Created: 2018-02-16
+    Discussion: https://github.com/bitshares/bitshares-core/issues/583,
+                https://github.com/bitshares/bitshares-core/issues/672
+    Replaces: -
+    Worker: To be done
+
+# Abstract
+
+Currently, when a short position's collateral ratio is below MCR (a parameter
+in price feed: `maintenance_collateral_ratio`) but is not completely filled
+immediately due to a lack of enough volume on the opposite side of the market,
+it will hang in the market and be waiting for being margin called.
+
+The owner then can adjust the order's collateral ratio **only if**
+* to close the position, or
+* the new collateral ratio is above MCR, or
+* the call order get completely filled (margin called) immediately.
+
+While this prevents shorters from maliciously reducing collateral ratio (to
+increase possibility of black swan event), it also prevents shorters from
+slightly increasing collateral ratio (to decrease possibility of black swan
+event).
+
+This BSIP proposes a mechanism to improve this situation.
+
+# Motivation
+
+Make the exchange system more user-friendly.
+
+# Rationale
+
+The ecosystem would get benefit if shorters are allowed to reduce risks to
+themselves while reducing risks to the system at same time.
+
+Current rules are a bit too strict, which can be loosed to:
+
+A shorter can adjust the position's collateral ratio **only if**
+* to close the position, or
+* the new collateral ratio is above MCR, or
+* the call order get completely filled (margin called) immediately, or
+* **the new ratio is higher than old ratio and debt is not increased**
+
+# Specifications
+
+In `do_apply()` function of `call_order_update_evaluator` class, if
+finally found the call order still in margin call territory,
+* don't throw an exception if `call_obj->collateralization()` is reduced, and
+* require `delta_debt` of `call_order_update_operation` to be non-positive.
+
+# Discussion
+
+[to be added if any]
+
+# Summary for Shareholders
+
+[to be added if any]
+
+# Copyright
+
+This document is placed in the public domain.
+
+# See Also
+
+* https://github.com/bitshares/bitshares-core/issues/583
+* https://github.com/bitshares/bitshares-core/issues/672
+* https://bitsharestalk.org/index.php?topic=25926.0