Ch 15 Data Sharing Myungchul Kim

2 o DBMS: a form of storage middleware o XML o Transaction processing o Database management – Aggregation and sharing (Fig 15.1)

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4 o The Relational model – A relational DBMS stores data in tables with rows and columns. – Fig 15.2 and 15.3

5 – Fig 15.5

6 o Objects and tables – An object instance corresponds to one row of a table, and an object class corresponds to the structure of the table – its fields (names and data types). – Fig 15.6

7 o Differences between object and relational models – The program code representing the methods – Objects can encapsulate data through methods – Application logic – Queries

8 o Documents and XML – Makeup language: a hierarchical structure for a document – Standard General Markup Language by ISO – A simplified subset of SGML: Hypertext Markup Language (HTML) focusing on the presentation of documents – eXtensible Markup Language (XML) by W3C – Fig 15.7

9 o Transaction processing – Transaction: a group of related resource management actions that are atomic – Commit or abort – Fig 15.8

10 o Transaction protocol – Allow locking of resources – Roll back and logging – Voting protocol: two-phase commit (prepare, commit or abort)

11 o IT Pro, May & June 2000, pp – A language for organizing data – Lets you define your own customized markup languages for different documents classes – Define your own custom tags – Fig 1 XML: Data’s Universal Language

12 – Unicode – A rooted tree structure o Document type definition (DTD) defines an XML grammar – What markup tags are available – Where they may occur, and – How they all fit together.

13 – Fig 2

14 – Fig 3

15 o Key application areas – Let you reformat data for multiple devices and platforms – Meta-information: search and retrieve documents efficiently – Messaging: seamless and efficient transfer of data o Limitations – Efficient low-level communication – Lack of standard vocabularies or tag sets – Security: ssl, digital signature, …