1. 1 CS851 Data Services in Advanced System Applications Sang H. Son son@cs.virginia.edu

2. 2 What is Data Service? v Need for proper functioning of applications v Same/similar to queries and transactions in database systems? v A database models real-world enterprise. – Entities (e.g., students, courses) – Relationships (e.g., Alexander is taking CS851) v What is Database Management System (DBMS) ? v A software system designed to store and manage databases v Queries and transactions: key aspects of DBMS

3. 3 Current Trends in Advanced Applications v Interaction with the physical world/entities v Dynamic data; real-time data; temporal data v Sophisticated in their data needs v Raw sensor data vs aggregated or derived data v Huge volume v Real-time or near real-time access v Large scale v Resource constraints

4. 4 Why Study Data Services? v Shift from DBMS to data services – Extensions of traditional DBMS – Advanced applications present different requirements: application-centric and data-centric v Datasets increase in diversity and volume – Digital libraries, interactive video, sensor networks, stream data, gene/biological data, satellite images –... need for data services exploding v DBMS is a key component in data service system architecture ?

5. 5 Key Ideas of DBMS – Schemas/Views v Many views, single conceptual (logical) schema and physical schema. v Views describe how users see the data. v Conceptual schema defines logical structure v Physical schema describes the files and indexes used. Physical Schema Conceptual Schema View 1View 2View 3

6. 6 Key Ideas - Data Independence v Applications insulated from how data is structured and stored. v Logical data independence : Protection from changes in logical structure of data. v Physical data independence : Protection from changes in physical structure of data.

7. 7 Key Ideas - Transactions v Key concept is transaction, which is an atomic sequence of database actions (reads/writes). v Each transaction, executed completely, must leave the DB in a consistent state if DB is consistent when the transaction begins. v Users can specify integrity constraints on the data; DBMS enforces these constraints. v Ensuring that a transaction (run alone) preserves consistency is ultimately the user’s responsibility!

8. 8 Applications to Study in CS851 v Real-time systems v Stream data management v Wireless sensor systems v Dynamic data dissemination

9. 9 Issues in Those Applications v Real-time systems – Freshness and timeliness – QoS and robustness v Stream data management – Monitoring, operator scheduling, load shedding v Wireless sensor systems – Event service, data aggregation and dissemination v Dynamic data dissemination – Coherence preservation, adaptive push and pull v Wide variety of applications – application specific issues

10. 10 Application Spectrum of WSN

11. 11 Key Components in CS851 v Paper selection by next Tuesday v Paper presentation –Draft slide submitted at least 2 days before the scheduled presentation date –Presentation of main ideas/contributions –Examples and animation –Discussions and critiques v Paper reading and summary/critique submission v Project proposal v Project presentation and final report submission v Best presentation award