1. Compiling Mappings to Bridge Applications and Databases Melnik, Adya and Bernstein @Microsoft Research

2. Introduction Application Model VS Database Model Reasons Approaches Client side mapping layer -Providing updatable views on DB ADO.NET Entity Framework Declarative mappings Bidirectional views Query view : app = view(DB) Update view: DB = view(app)

3. Mapping Approach Mapping Specification Entity SQL + XML Mapping fragment: Mapping Compilation Bidirectional views Query views + Update Views Properties Entities = QueryViews(Tables) Tables = UpdateViews(Entities) Entities = QueryViews(UpdateViews(Entities)) - Roundtripping criterion Execution ▲ Tables = ▲ UpdateViews(Entities, ▲ Entities) ▲ Tables = ▲ UpdateViews(QueryViews(Tables), ▲ Entities) Merge Views : S upd X S old → S new

4. Mapping Compiling Problems Data roundtrips map o map -1 = Id(C) u subset map subset q -1 Merge Views S upd X S old → S new Biparite Mappings map = f o g -1 f : C → V g : S → V

5. View Generation Overview Query view q = f’ o g, where f’ : V → C Update View Schema partition Merging view An example

6. View Generation Partitioning Schema Mapping language dependent Goals: Allowing expressing each fragment query in map as a union query over the partitions

7. View Generation Reconstructing partitions Injectivity holds only if the partitions can be reconstructed from the views

8. Conclusion A new mechanism supporting updatable views Formulating mapping compilation problems and algs. Implemented in Commercial Product