How to define and implement properties in protocol

I want to define one protocol with few properties and need to use those properties in another NSObject subclass. Please give me link or example code. I need that to work with 10.5.

Thanks PLEASE CHECK THE FOLLOWING SAMPLE CODE

@protocol MyProtocol
@property (nonatomic, readonly) id someObject;
@property (nonatomic, getter=isAlive) BOOL alive;
@end

#import "MyProtocol.h"
@interface MyCustomClass : NSObject <MyProtocol>{

}
@end

#import "MyCustomClass.h"
@implementation MyCustomClass
@synthesize someObject,alive;

/*
- (id)someObject {
    return nil;
}

- (BOOL)isAlive {
    return YES;
}

- (void)setAlive:(BOOL)aBOOL {
}
*/
@end

**Added: Compling code with x86_64 architecture works fine. But error if i'll change the architecture to i386, then i am getting following warnings:

MyCustomClass.m:13: error: synthesized property 'someObject' must either be named the same as a compatible ivar or must explicitly name an ivar

 error: synthesized property 'alive' must either be named the same as a compatible ivar or must explicitly name an ivar

I just want to know why it is working in x86_64 with @synthesize and not in i386.**