OData & SAP Gateway Essentials

What are the four subconstraints of REST's uniform interface, and which is the one most APIs actually skip?

You configure the SAP system alias on a central hub Gateway exactly the way the embedded-deployment guide shows (alias LOCAL, Local GW checked, RFC destination NONE). What breaks?

A client sends a PUT to update just one property of an OData entity and is surprised the other fields got wiped. What did they get wrong, and what should they have used?

You need to fire a controlled test OData request (set the HTTP method, headers, body) against a service from inside the SAP system. Which built-in tool, and where do you launch it?

Management asks why you'd expose a Fiori app through OData/Gateway instead of a direct RFC/BAPI call. What is the architecturally significant reason (not 'it's a standard')?

A developer appends $metadata to a service URL expecting to see the records and gets an XML schema instead. What does $metadata actually return, and in what language?

What is OData, and which technologies is it built on?

A developer tries to page an OData result set with $page and it's ignored. Why, and how is paging actually done?

Two documents hang off an OData service root. If you need the property/type structure of an entity (not just which collections exist), which one do you read — and what does the other give you?

An OData association between Customer and SalesOrder is modeled, but the client can't tell whether a customer has one order or many. Which declared part of the association ends is missing?

From which existing SAP artifacts can SAP Gateway service objects be generated?

OData service calls fail right after a fresh setup even though the service is registered. Before chasing the service, what system-level switch must be on, and where?

You create the SM59 destination for the trusted RFC from Gateway to the Business Suite. Which settings make it a trusted (not just plain) RFC, and what is easy to get wrong?

Which six constraints must an application satisfy to count as RESTful, and which is the one people wrongly drop?

A team assumes that to consume an SAP Gateway service their mobile app must use an SAP SDK and someone who knows ABAP. Correct them.

OData services are described as read APIs that feed the Fiori UI. Why is that picture wrong, and what's the practical consequence?

The trusted RFC is created on the front end, but the trust relationship still doesn't work. Which two steps were skipped?

You want the products belonging to supplier 0 via an OData URI. How do you express 'supplier 0, then its products', and what makes that traversal possible?

In the OData metadata document, where are the service's entity sets actually defined, and can the service document list different ones?

A user's Fiori UI comes up in the wrong language through Gateway. What do you check, and in what order?

You're granting SAP Gateway admin rights from role template /IWFND/RT_ADMIN. Why not just assign the template directly, and what's the correct sequence?