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  1. PO
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    <p>I think your setup is too complicated. Also, you set up your relationships a bit like <em>sub-classes</em>. But relationships and sub-classes are completely different concepts, and I think you might be mixing them up.</p> <p>Here is what I propose:</p> <p>Have an entity <strong>Location</strong>, with attributes <strong>latitude</strong>, <strong>longitude</strong> and <strong>name</strong>. Set <strong>latitude</strong> and <strong>longitude</strong> as non-optional, but <strong>name</strong> as optional. Now you have all the basic building blocks you need.</p> <p>In your code you can define objects such as *POI of type <strong>Location</strong>, *destination of type <strong>Location</strong> and *startPoint of type <strong>Location</strong>. You can use the coordinates to calculate the shortest route for example. By setting the <strong>name</strong> you can make any <strong>Location</strong> into a POI. If you want names for non-POIs, create a boolean attribute <strong>isPOI</strong>. </p> <p>Now, if you want to store specific travel routes, you can introduce an entity <strong>Route</strong>, with attributes like <strong>name</strong>, <strong>date</strong> etc. and a one-to-many relationship to <strong>Location</strong>. Note that you can not put the many <strong>Locations</strong> in any particular order with this scheme. However, what you could do is include two more one-to-one relationships to <strong>Location</strong>, one called <strong>startLocation</strong> and one <strong>destination</strong>. </p> <p>If you really need a more complex description of itineraries in your core data model, you probably need another entity. You could call it <strong>TravelPoints</strong> with a many-to-one relationship to <strong>Route</strong>, a one-to-one relationship to <strong>Location</strong> and attributes like <strong>arrivalDate</strong>, <strong>timeStayed</strong> or <strong>departureDate</strong>, <strong>sequentialNumber</strong> (to indicated the order in <strong>Route</strong>), etc. </p> <p>With this setup you should be able to go far with your project.</p>
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    1. POProblem with property inherited from parent entity
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    1. COHow sub class in core data different from real sub class ? The problem is when I set one property (Destination) it got mixed up with another one (POI) which it shouldn't. Do you have any document or reference on this situation, Thank you.
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    2. COA real subclass inherits properties from its superclass and extends these or overrides the default ones. When you define a Location as a Route's destination and that Location is also a POI you just a have additional information which you can use or not. So I do not see any problem. -- In general you want to avoid too many "subclass-like" one-to-one relationships if you can encapsulate that information in just one entity.
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    3. COThe problem about performance is one thing, but now I got problem on property mixed up (calling route.points also return destination).
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