Centralized vs Distributed Homogeneous vs Heterogeneous Federated DB

• Centralized vs. Distributed • Homogeneous vs. Heterogeneous – Federated DB, Multi-Database • General Purpose vs. Special Purpose • Main Memory Database – MM, Secondary Storage, Tertiary Storage

Data Base Management System (DBMS) データベースを作成 し、維持する為の プログラム群 USER Application Program DBMS Query Processor Access Method Meta Data Base System Database

Data Independence(データ独立） • Program-Data Independence – External Scheme & Conceptual Scheme • Logical/Physical Data Independence – Conceptual Scheme & Internal Scheme • Program-Operation Independence – O-O

３層スキーマ External View Conceptual Scheme Internal Scheme External View

Transaction 管理 • ＡＣＩＤ – Atomicity – Consistency – Isolation – Durability • データ共有時における一貫性の維持

Merits and Demerits • Merits – Reduced Application Development Time No care for Concurrency Control, Access Method Recovery, Integrity Checking – Flexibility by Shared View ←　Data Independence • Demerits – Needs more power

DBA DDL Casual Query Programmer ＡＰ preprocessor Dictionary DDLcompiler Catalog Query Compiler DML Host Lang. DMLcompiler. Compiler Compiled Transaction Concurrency Cont Backup/Recovery Access Methods Run Time Processor DB

2. データモデル • Data Model is a set of concepts that can be used to describe the structure of database – Data type, relationship, constraint • High Level Data Model – Entity Relationship Model • Entity: 実体（real world object, concept) – Eg. Employee, Project • Attribute: entitityを記述する属性 • Relationship: entity間の関係

• Representational Data Model – Relational Model – Network Model – Hierarchical Model – OO Model – OR Model

Scheme and Instance • Scheme – Student[name, id, address, phone#] • Instance – [鈴木大地、0011, 神奈川県横浜市、0903223333] • Database State = set of instances

ＥＲ－model • Entity-Relationship Model – Popular conceptual data model – Database design tool で広く利用