Top-down design process An iteration of five steps Requirements Analysis Requirement analysis Conceptual design and (Objectives) View integration Design. view Integratio Design E-R representation and Global Conceptual Access External Schema translation to rdb schema Schema. Informatione Definition Distribution design Distribution User Input Data fragmentation and cal Conceptual allocation Physical design Tuning Feedback- Observation and Feedback 2021/2/1 WAMDM Cloud Group
Top-down design process • An iteration of five steps: – Requirement analysis – Conceptual design and view integration E-R representation and translation to RDB schema – Distribution design Data fragmentation and allocation – Physical design – Tuning 2021/2/11 WAMDM Cloud Group 11
Bottom-up design process Primarily for multidatabase applications · Terms related Data integration/fusion P2P Not covered by this course 2021/2/1 WAMDM Cloud Group
Bottom-up design process 2021/2/11 WAMDM Cloud Group 12 • Primarily for multidatabase applications • Terms related – Data integration/fusion – P2P • Not covered by this course
Distribution Design Issues Why to fragment How to fragment Correctness of fragmentation How to allocate The information for fragmentation 2021/2/1 WAMDM Cloud Group
Distribution Design Issues • Why to fragment • How to fragment • Correctness of fragmentation • How to allocate • The information for fragmentation 2021/2/11 WAMDM Cloud Group 13
Reasons for fragmentation To enhance intra-query concurrency To increase the throughput But extra cost for queries involving more than one segment residing at different sites 2021/2/1 WAMDM Cloud Group
Reasons for fragmentation 2021/2/11 WAMDM Cloud Group 14 To enhance intra-query concurrency To increase the throughput But extra cost for queries involving more than one segment residing at different sites
Correctness for rules of fragmentation Completeness If R is decomposed into RI, R2,, R, then for any data item d d∈R→>d∈Rs( one or more r, Isin) Reconstruction If R is decomposed into R,, R,,,R,, then 3v, s.t R=R1VR2V…VR where v is a relational operation Disjointness If R is horizontally decomposed into R,, R,,,R, then R∩R=d for any i and j,S.t.1≤i, isn and i≠ 2021/2/1 WAMDM Cloud Group
Correctness for rules of fragmentation 2021/2/11 WAMDM Cloud Group 15