Fixed Value on a Composite Key Relationship

Can you please help me with a possible solution for the following problem. 
I have a table (Pets) that consists of a Composite key. (I modelled this with a unique Index) However when I create my form Bookings (Has 2 relationships to Pets, 1 for Cats and 1 for dogs) On the Cat field it should only show the names of the Cats when I use the Lookup and on the Dog field it should only show the list of Dogs from the Pet table.  This is used frequently through out the system, in fact nearly all the Relationships to this table should only show certain types of pets.  How can I build something reusable to use on my forms.  I have attached an example of the problem.
Kind regards
After looking at this for a few seconds it looks like it's just a little poor design in your schema.  Why do you need separate foreign keys to the same Pets entity when you have a PetType field?  Using that field will allow you to do everythng you want.  What happens when you add the third and fourth type of pet?  You can't just keep adding foreign keys - defeats the whole purpose of a good normalized database schema.

If you rework this with one foreign key to Pets and use the PetType as a selection criteria you should be able to accomplish everythng you want.

Hope this helps,

Hi Curt .  Thanks for your response
This is a very simplified example of what is required.  I understand what you are saying here but in our case there is a lot more complexity.  If I did change the model to only have 1 relationship, how would I filter Pets (
use the PetType as a selection criteria) to only show the cats if I so wanted?  I think that is more the problem.  I do not know how to filter the selection criteria on what is being shown from my Foreign key lookup.
Still a new Outsystems developer.
There are a large number of ways to accomplish what you want but you definitely want one and only one foreign key regardless of what the user sees.  As a new Outsystems developer, I recommend viewing the tutorials (if you haven't already) and looking at existing components in the Forge to see how others accomplish similar functionality. 

In the Forge there is an application called Directory (just search the forge for that) that does a very good job of showing how a user can select different records based on type.  If you download and examine the code a little, you'll see how that is done and you can model your code after it.

Hope that helps,