How do I programmatically access CDS annotations on entities?

I understand that you can have user-defined annotations on a CDS entity (http://help.sap.com/saphelp_hanaplatform/helpdata/en/fd/2a79e92a374d3596950d97f5386ba8/content.htm?frameset=/en/82/17aac86d9748d8b034797ecc8065b6/frameset.htm&current_toc=/en/34/29fc63a1de4cd6876ea211dc86ee54/plain.htm&node_id=103).

How can you programmatically access these annotations at runtime?

I found a blog post (New Data Modeling Features in SAP NW ABAP 7.4 SP5) that stated that "Annotations can be used to add metadata to CDS entities. Annotations specify the properties and semantics of the entity and its behaviour when it is accessed at runtime. This metadata can also be accessed by consumption tools using special APIs." What are these APIs?

Thanks.