Filter by reference Filter by reference is a mechanism by which the referred syncbo’s get downloaded only if its corresponding referring syncbo’s are present on the mobile device. So, the referred syncbo that does not have corresponding referring syncbo will not get downloaded to the mobile device during synchronization. Filter by reference is set for referred syncbo only. Before you proceed, I would request you to go through my previous blog ‘Exclusive coverage on cascade download behavior’ so that you understand this topic easily. If you already have, lets proceed without taking diversion. Let’s consider two syncbo’s in design time where the cascade flag ( C ) is set for relation and filter by reference( R ) is not set for Syncbo B. 
Note : Here only cascade download flag is set and not the filter by reference. Lets create instances of these syncbos.
Case 1: when mobile device synchronizing syncbo A and Syncbo B in sequence. Step a : Mobile device synchronizing syncbo A. 
After synchronizing Syncbo A, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Step b: Mobile device synchronizing syncbo B after Syncbo A (step a). 
After synchronizing Syncbo B, These instances will be present on the device. Syncbo B : 1bTop, 1b010, 3bTop,3b010. Syncbo A : 1aTop, 1a010. Note : Here referred Syncbo 3b[3bTop, 3b010] which does not have physical existance of referring Syncbo 3a[null, null] entity gets downloaded to the device unnecessarily. Have you ever tought of this scenario. How do we prevent such unnecessary download of synchronization objects on to the mobile device ? The solution is to use filter by reference. Let’s consider two syncbo’s in design time where the cascade flag ( C ) is set for relation and filter by reference( R ) is set for Syncbo B.
Note : Here both cascade download flag and filter by reference flag is set. Lets create instance of these syncbos.
Case 2: when mobile device synchronizing syncbo A and Syncbo B in sequence. Step a: Mobile device synchronizing syncbo A. 
After synchronizing Syncbo A, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Step b: Mobile device synchronizing syncbo B after Syncbo A (Step a). 
After synchronizing Syncbo B, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Note : Here Syncbo 3b[3bTop, 3b010] is not downloaded to the device. ********************END************************** NOTE : The blog on Non cascade download behavior will be published shortly. Till then enjoy cascading and filter by reference.
Note : Here only cascade download flag is set and not the filter by reference. Lets create instances of these syncbos. Case 1: when mobile device synchronizing syncbo A and Syncbo B in sequence. Step a : Mobile device synchronizing syncbo A. After synchronizing Syncbo A, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Step b: Mobile device synchronizing syncbo B after Syncbo A (step a). After synchronizing Syncbo B, These instances will be present on the device. Syncbo B : 1bTop, 1b010, 3bTop,3b010. Syncbo A : 1aTop, 1a010. Note : Here referred Syncbo 3b[3bTop, 3b010] which does not have physical existance of referring Syncbo 3a[null, null] entity gets downloaded to the device unnecessarily. Have you ever tought of this scenario. How do we prevent such unnecessary download of synchronization objects on to the mobile device ? The solution is to use filter by reference. Let’s consider two syncbo’s in design time where the cascade flag ( C ) is set for relation and filter by reference( R ) is set for Syncbo B.Note : Here both cascade download flag and filter by reference flag is set. Lets create instance of these syncbos. Case 2: when mobile device synchronizing syncbo A and Syncbo B in sequence. Step a: Mobile device synchronizing syncbo A. After synchronizing Syncbo A, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Step b: Mobile device synchronizing syncbo B after Syncbo A (Step a). After synchronizing Syncbo B, These instances will be present on the device. Syncbo B : 1bTop, 1b010. Syncbo A : 1aTop, 1a010. Note : Here Syncbo 3b[3bTop, 3b010] is not downloaded to the device. ********************END************************** NOTE : The blog on Non cascade download behavior will be published shortly. Till then enjoy cascading and filter by reference.