Understanding Networked Applications:
A First Course
Chapter 15
by
David G. Messerschmitt
Understanding Networked Applications:
A First Course
Databases
by
David G. Messerschmitt
Databases
• Treat data as a separate asset
– May be shared by multiple applications
• Provide protection and integrity features
appropriate to mission-critical data
–
–
–
–
Access control
Integrity constraints
Persistence
etc.
Understanding Networked Applications
3
A First Course
Two capabilities
Application I
Aggregation: accessing
multiple databases
Application II
Sharing: two or more
applications accessing the
same databases
Databases
Understanding Networked Applications
4
A First Course
Relational table
Table
Employee
Name
Address
Dept
Record
Field
Understanding Networked Applications
5
A First Course
Database operations
Employees
Departments
Each operation
results in a new
table, so they can
be concatenated
“PROJECT”
“SELECT”
Understanding Networked Applications
6
A First Course
Multiple tables
“PROJECT”
Understanding Networked Applications
“SELECT”
7
A First Course
Record at a time processing
Database
Application logic
(system
programming
language)
SQL
Understanding Networked Applications
8
A First Course
SQL interface
• Presents single abstract interface to the application
logic
• Standardized, not vendor specific
– “Stored procedures” and “extensions” violate this
• Encapsulates various internal details
–
–
–
–
Data partitioning and replication
Host mapping
File representation
etc.
Understanding Networked Applications
9
A First Course
Fields, columns, attributes
Records,
rows
Year
2002
2002
2002
2002
2002
2002
2002
2002
2002
2003
2003
2003
2003
2003
2003
2003
2003
2003
City
Oakley
Oakley
Oakland
Oakland
Berkeley
Berkeley
Berkeley
Albany
Albany
Oakley
Oakley
Oakland
Oakland
Berkeley
Berkeley
Berkeley
Albany
Albany
Accommodation
Bed&Breakfast
Resort
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Bed&Breakfast
Resort
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Understanding Networked Applications
Tourists
14
190
340
230
120000
3450
390800
8790
3240
55
320
280
210
115800
4560
419000
7650
6750
10
• Entries are
simple data types
or compositions of
those types
• Integrity
constraints
A First Course
Object/table correspondence
Class
Class
implementation
Record-at-a-time
program
Employee
Name
Address
Dept
Object instance data
Attribute
Understanding Networked Applications
11
A First Course
Object attributes
Object
instances
Year
2002
2002
2002
2002
2002
2002
2002
2002
2002
2003
2003
2003
2003
2003
2003
2003
2003
2003
City
Oakley
Oakley
Oakland
Oakland
Berkeley
Berkeley
Berkeley
Albany
Albany
Oakley
Oakley
Oakland
Oakland
Berkeley
Berkeley
Berkeley
Albany
Albany
Accommodation
Bed&Breakfast
Resort
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Bed&Breakfast
Resort
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Resort
Camping
Bed&Breakfast
Understanding Networked Applications
Tourists
14
190
340
230
120000
3450
390800
8790
3240
55
320
280
210
115800
4560
419000
7650
6750
12
• Rows can be
considered object
instances with the
same attributes
• Restriction to
simple data types
• No encapsulated
state
• No methods
A First Course
Object-relational database
• A column can store object
instances of a given class
rather than data of a given
simple or compound data
type
• Because of the table
structure, SQL can be
extended to this case
• Standard SQL queries
can be extended to
methods returning simple
data types
• Many other good ideas
Understanding Networked Applications
13
A First Course
Benefits of ORDBMS
• Extension: manage arbitrarily complex data types
• Migration: preserve and extend existing databases
• Preserve SQL interface
– OR extensions in latest standard
• All the benefits/experience of earlier databases
– Access control, data integrity, persistence, etc.
• Killer app: Behind Web/CGI
– Images, video, audio, animation, applets, etc.
Understanding Networked Applications
14
A First Course
Understanding Networked Applications:
A First Course
Markup languages
by
David G. Messerschmitt
Definition
• A markup language describes the structure
of a document
– Based on tags
– Tags denote structural elements like sections,
subsections, figures, etc
• Internationally standardized, so application
independent
Understanding Networked Applications
16
A First Course
Example: HTML
HEAD>
<META NAME="GENERATOR" CONTENT="Adobe PageMill 2.0 Win">
<TITLE>David G. Messerschmitt Homepage</TITLE>
</HEAD>
<BODY ALINK="#c4124e" BACKGROUND="Images/background.jpg">
<H3>&nbsp;</H3>
<BLOCKQUOTE>
<H2><TABLE BORDER="5" CELLSPACING="2" CELLPADDING="0">
<TR>
<TH> <P ALIGN=LEFT><IMG SRC="Images/Messer.gif" WIDTH="112" HEIGHT="168" ALIGN=
"BOTTOM" NATURALSIZEFLAG="3"></TH></TR>
</TABLE>
</H2>
<H2><BR>
David G Messerschmitt</H2>
<H3>Roger A. Strauch Professor of <A
HREF="http://www.eecs.berkeley.edu/">Electrical
Engineering and Computer Sciences</A></H3>
Understanding Networked Applications
17
A First Course
Family lineage
SGML
XML
HTML
Emphasizes
formatting and
presentation of
documents
Emphasizes
structure of
documents
Understanding Networked Applications
18
Purpose- and
industry-specific
extensions
A First Course
Data sharing among applications
• Options include:
–
–
–
–
Messages with defined formats
Documents (eg. XML)
Shared databases
Remote method invocation middleware
• The first two are the most practical for interenterprise applications
Understanding Networked Applications
19
A First Course