  We study the problem of pliable private information retrieval with side
information (PPIR-SI) for the single server case. In PPIR, the messages are
partitioned into nonoverlapping classes and stored in a number of noncolluding
databases. The user wishes to retrieve any one message from a desired class
while revealing no information about the desired class identity to the
databases. In PPIR-SI, the user has prior access to some side information in
the form of messages from different classes and wishes to retrieve any one new
message from a desired class, i.e., the message is not included in the side
information set, while revealing no information about the desired class to the
databases. We characterize the capacity of (linear) single-server PPIR-SI for
the case where the user's side information is unidentified, i.e., the user is
oblivious of the identities of its side information messages and the database
structure. We term this case PPIR-USI. Surprisingly, we show that having side
information, in PPIR-USI, is disadvantageous, in terms of the download rate,
compared to PPIR.
