Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| CCC | IEEE Conference on Computational Complexity | 1993 | 1996 | 1999 | - | 2007 | 2011 | 2015 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| EC | ACM Conference on Electronic Commerce | - | - | - | 2003 | 2007 | 2011 | 2015 |
| ISCA | ACM/IEEE International Symposium on Computer Architecture | 1993 | 1996 | 1999 | 2003 | 2007 | 2011 | 2015 |
| LCTES | ACM SIGPLAN/SIGBED Conference on Languages, Compilers, and Tools for Embedded Systems | - | - | 1999 | 2003 | 2007 | - | - |
| METRICS | ACM SIGMETRICS International Conference on Measurement and Modeling of Computer Systems | - | 1996 | 1999 | 2003 | 2007 | - | 2015 |
| PLDI | ACM SIGPLAN Conference on Programming Language Design and Implementation | - | 1996 | 1999 | 2003 | 2007 | 2011 | 2015 |
| PODC | ACM Symposium on Principles of Distributed Computing | - | 1996 | 1999 | - | - | 2011 | - |
| PPoPP | ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming | 1993 | - | 1999 | 2003 | - | - | - |
| SPAA | ACM Symposium on Parallelism in Algorithms and Architectures | - | - | - | 2003 | 2007 | 2011 | 2015 |
| SoCG | ACM Symposium on Computational Geometry | 1993 | 1996 | - | 2003 | - | - | - |
| STOC | ACM Symposium on Theory of Computing | 1993 | 1996 | 1999 | 2003 | 2007 | 2011 | 2015 |
Question:
which conference had their last year as 2011?
Answer:
ACM Symposium on Principles of Distributed Computing