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Database management systems: |
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Provide efficient and secure access to large
amounts of data. |
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Address problems such as: |
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How to store the data |
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How to query data efficiently |
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How to update the data securely (by multiple
users) |
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Contrast with using file systems for the same
task |
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Based on the relational model |
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Separates the logical view from the physical
view of the data. |
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Find all the students who have taken 94.301 in
Fall 2001. |
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S(tructured) Q(uery) L(anguage) |
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select E.name |
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from Enroll E |
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where E.course=94.301 and |
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E.quarter=“Fall 2001” |
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Query processor figures out how to answer the
query efficiently. |
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Relational databases are a great success of
theoretical ideas. |
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“Big 3” DBMS companies are among the largest
software companies in the world. |
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IBM (with DB2) and Microsoft (SQL Server,
Microsoft Access) are also important players. |
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$20B industry |
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Challenged by object oriented DBMS. |
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Storage management |
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Abstract data model |
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High level query and data manipulation language |
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Efficient query processing |
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Transaction processing |
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Resiliency: recovery from crashes |
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Interface with programming languages |
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Data independence and efficient access. |
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Reduced application development time. |
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Data integrity and security. |
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Uniform data administration |
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Concurrent access and recovery from crashes. |
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Several aspects: |
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Modeling and design of databases |
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Database programming: querying and update
operations |
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Database implementation |
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DBMS study cuts across many fields of Computer
Science: OS, languages, AI, Logic, multimedia, theory... |
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Why do we need it? |
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Agree on
structure of the database before deciding on a particular implementation. |
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Consider issues such as: |
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What entities to model |
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How entities are related |
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What constraints exist in the domain |
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How to achieve good designs |
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Object Definition Language (ODL): |
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Closer
in spirit to object-oriented models |
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Entity/Relationship model (E/R): |
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More relational in nature. |
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Both can be translated (semi-automatically) to
relational schemas (with varying amount of pain). |
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ODL to OO-schema: direct transformation (C++ or
Smalltalk based system). |
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Is part of ODMG, which also gave us OQL. |
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Resembles C++ (and Smalltalk). |
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Basic design paradigm in ODL: |
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Model objects and their properties. |
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For abstraction purposes: |
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Group objects into classes. |
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What qualifies as a good class? |
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Objects should have common properties. |
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Notes