Entity relationships can't be stored

Data Service
1

I’m trying to save a very simple entity graph from my iOS app.
One to many relationship between “Program” and “Events” see the output below.

@interface Event : NSObject

@property (nonatomic, strong) NSString *objectId;

@property (nonatomic, strong) NSDate *startsOn;

@property (nonatomic, strong) NSDate *endsOn;

@property (nonatomic, strong) NSDate *created;

@property (nonatomic, strong) NSDate *updated;

@end

@interface Program : NSObject

@property (nonatomic, strong) NSString *objectId;

@property (nonatomic, strong) NSString *title;

@property (nonatomic, strong) NSDate *created;

@property (nonatomic, strong) NSDate *updated;

@property (nonatomic, strong) NSMutableArray *scheduledPrograms;

-(void)addEvent:(Event *)event;

@end

2013-11-17 21:35:20.610 Vista Mobile[14113:70b] {

created = "<null>";

objectId = "<null>";

scheduledPrograms =     (

    "<Event: 0xb61e1b0>",

    "<Event: 0xb62c080>",

    "<Event: 0xb63a9a0>"

);

title = ddddddsdfsdfsdfdsfsdf;

updated = "<null>";

}

2013-11-17 21:36:21.058 Vista Mobile[14113:70b] Failure The request timed out.