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History of Implementation Data Models Databases were: • Early Business Computer Systems – Accounting functions - payroll, profit/loss statements • Files of data - file oriented (physical hardware) – sequential and random access (index) In 1960's needed: • • • • Integrated centralized data structure Redundancy DBA's Data models Mid 1960's - Hierarchical data model • • • • • logical level - data relationships relationships structured as hierarchies parents and children child can have only 1 parent 1-to-many Hierarchical Example Store products supplier manu customer Invoice To query Hierarchical • Used pointers • Any query through the data followed pointers • manipulated 1 row at a time For each store: Get next store For each product: Get next product For each supplier: Get next supplier Process supplier Hierarchical DB • Problems? – How to represent many-to-many relationships? Late 1960's - Network Model • • • • Many-to-many relationships More than 1 parent Records a member in a set Owner-Member Relationship – Implemented as circular linked lists • A child may appear multiple times in each circle • Can implement with pointers to objects disk • Excellent retrieval performance Network example Store customer (owner) Product (member) Supplier customer (owner) Invoice (member) Network Query language: Move Find Get Still had to specify a record at a time Network • Similar to hierarchical – Get next, etc. • Precursor to object-oriented • Problems? – Query language 1970's Relational Model - E.F. Codd • Rows and Columns • Easier to write queries Relational example Product: PID type price supplierID Supplier: SID location Relationships? Primary and Foreign key Relational • Instead of 1 record at a time, files or sets at a time Select PID, location From Customer, Supplier Where supplierID = SID • Problems? 1980's Object-Oriented DBs • Represent real-world entities as objects – Objects and relationships – Classes and instances – Specialization /Generalization – Inheritance, methods • Similar to network model Object-Oriented DBs Product ID type price Supplier Supplier ID location Object-Oriented DBs • To query use ObjectSQL – dot notation Select ProductID, Supplier.location From Product • Most versions based on relational • Problems? 1990’s – Issues/Advances • Object-Relational DBs – extend relational – Keep relational, but add OO features • Additional Issues: – Distributed DBs – Data mining and data warehouses – Real-time Databases 2000’s – DB Issues/Advances • • • • • Data integration Database Security Mobile Databases Data-intensive computing - Data Grids NoSQL – Sensor Databases – Web Databases & Information Retrieval – XML Databases (hierarchical) 2010’s Issues • Cloud computing - where do databases fit in? – Information retrieval / Text processing • BIG Data • • • • Green Computing Data driven decisions Data is the next frontier Other suggestions?