COMS W3156:Software Engineering, Fall 2001

Lecture #19: Databases, CVE’s

Janak J Parekh

janak@cs.columbia.edu

Administrativia• Prototype status

• New schedule adopted

• Guest lecture on Thursday

Next class

• Guest lecture!• It’s my friend, so you have to come • After that:

– Continue discussion on languages• Begin pointers

• C++

– Smooth your transition to future semesters

– Will anyone actually attend next Tues.? I really hope so

Today’s class

• Finish look at Swing/AWT– Recitation!

• Discuss side-topic of virtual environments in the software engineering world

• Brief discussion of databases

• Start C, the language

Swing/AWT layout management

• Need to lay out various components• Might use IDE for this, though I don’t• BorderLayout, GridLayout, CardLayout,

FlowLayout, GridBagLayout– Last one pain to do by hand

• Use JPanels to embed one in another• setPreferredSize()• Tip: draw out on paper first

Images (I)

• http://java.sun.com/docs/books/tutorial/uiswing/painting/usingImages.html

• Toolkit.getDefaultToolkit().loadImage(…)• Create a MediaTracker to wait for image to

load• Caching images: Java or you?• Drawing images: g.drawImage(…)

– Override paint method in the class

Images (II)

• Image transparency– Needed for object-on-tile– Use Photoshop or even the GIMP to edit

images– We linked to a set on the webboard– May release our modifications/subset

• Consider laying out tiles in a GridLayout

Images (III)

• Alternative image construct: ImageIcon

• Can embed in a JLabel

• Useful for buttons and other places where you don’t have access to Graphics context

• More awkward for actual game board

JTables

• Capable of showing complex data constructs fairly easily

• Set up a data model behind the table• Extend AbstractTableModel

– Specify the number of rows and columns– Specify what data is in each cell– Let the JTable do the rest

• JLists are similar: AbstractListModel• Can use Default{Table,List}Model: less useful

Actions

• JButton– addActionListener(new ActionListener()…)

• Keyboard– addKeyListener(new KeyAdapter()…)

– KeyEvent lets you check for most any key plus modifiers

• Right-click– addMouseListener(new MouseAdapter()…)

– Uses button masks (1.4 supports wheel!)

Miscellany

• JMenu/JMenuBar for menus– JPopupMenu – the name implies it all

• repaint(), revalidate()• JScrollPane to support scrolling of large areas

– Grid, perhaps? – Jsp.getViewport().setViewPosition(…) to force the

scrollpane around– Ideally, have it “follow” the player– Really necessary for JTables– http://java.sun.com/docs/books/tutorial/uiswing/componen

ts/scrollpane.html

Demos!

• JDK 1.3.1 demos– SwingSet: shows you all that’s out there– SampleTree– Only problem: these are large examples

Running Swing on CUNIX• Don’t• Why not?

– CUNIX is an old version of Solaris: 5.5.1 (SunOS 2.5.1), the latest version is 8 (SunOS 2.8)

• Double-versioning? Yes

– Apparently, AWT problems with JDK 1.3 and Solaris 5.5.1

– They’ve developed a horrible remote hack, but it doesn’t work properly

• Solutions: – if in 251, use local machine (xterm)

– if at home, download the JDK: it’s much faster anyway

– if you must use CUNIX, can try newcpunix.cc.columbia.edu

Sidebar: Collaborative Virtual Environments (CVE’s)

• Software development, if not done physically in teams, is a tricky proposition

• In fact, any work is a tricky proposition• Would like to see who else is working on a

project• Would like to see relation of data to each

other, and to people• 3D optimizes visual perception of data

Challenge

• How to present data in 3D in a meaningful way?

• Video conferencing?– Uhh, not quite– Phil sez: “Brady Bunch Model”

• Virtual “environments”– Avatars– Environment

• Traditionally static

CVE’s problem domains

• Web: why not look at it in 3D?– VRML – but it flopped: too frustrating– One of my startup ideas: from which our

Thursday speaker is coming

• Military simulations– Actually, already being used here

• Distributed software development– CHIME (interested?)

Databases: Overview

• One of the most popular and oldest computer applications

• A way of organizing data– File system is a “database” of sorts– Built off manual filing by clerks– Founded off 1890 census inventions

• Military and Social Security pushed dev– Social Security, 1935 (26 million records)

History

• http://www.nap.edu/readingroom/books/far/ch6.html

• 1950s: Notion of database as a separate entity from hardware, e.g. a database “system”

• 1960: COBOL established• 1968: IBM’s IMS for Apollo project• 1971: Codasyl (Conference on Data Systems

Languages) model

IMS and Codasyl

• IMS is/was a hierarchical database– Data has parents, children, siblings

– Move through a tree-like structure

• Codasyl model: “Network Data Model (NDM)”– Essentially, pointers between linked lists

– http://coronet.iicm.edu/Dbase1/courses/netdb/nur_html/ndm1.htm

• “The Programmer as Navigator”, Bachman, et. al., 1973

Rise of the Relational Model

• Ted Codd, at IBM

• “A Relational Model of Data for Large Shared Data Banks”, 1970

• Data independent of storage

• Queries are non-procedural and specified against the entire data set

• Not an immediately successful idea…

Relational Model Controversy• IBM had massive investments in IMS

– “Sole strategic product” == Codd is evil

• Codd was at IBM San Jose– Supposed to be building disk drives, not coming

up with new software paradigms– http://www.nap.edu/readingroom/books/far/ch6.ht

ml

• 10 years pass– 1973-9: Ingres at Berkeley with NSF/mil funding

• Open source success story!

– 1974-9: IBM develops System R SQL

Modern Databases

• Most everybody comes from Ingres– Oracle, Sybase, Informix

• SQL first commercially released by Oracle– Despite having been developed by IBM, they

blew the commercial market

• 1980: First relational database from IBM

• Ingres lives on: first postgres, then postgresql

Relational database fundamentals

• Data is stored as rows (records) in tables• Tables have columns (fields)• Here’s our current employee database:

• Set of tables organized into database

Name Address ID # Salary

Phil 118th St 3456 15000

Janak Long Island 5678 120000

SQL is Easy: Four Commands

• Select, Insert, Update, and Delete– “where” clauses can get tricky, though

• Select * from employee where salary > 20000• Insert into employee values(‘Suhit’,

‘Roosevelt Island’, 1010, 60000)• Update employee set salary = 120000 where

name = ‘Phil’• Delete from employee where id=1010

Manipulating databases

• Can use a front-end, like Access– Access has its own backend (the Jet database

engine) or can use a SQL backend

• Can programmatically work with a database– ODBC (Open Database Connectivity)– JDBC (Java Database Connectivity)– About as hard to work with as LDAP, more or

less

Theoretically Clean• All operations are on tables

• All return values are “rowsets”

• Query is actually sent as ASCII over the wire– Best strategy to answer is computed by database– Better than many traditional database mechanisms, which

actually move the whole database around (*cough*Access/Jet*cough*)

• Structure of database also stored in “system” tables

• There exists a Table of Tables, of course

Joins

• Why are databases relational?• Relate two tables based on common data column• Table with author-ID, author-full-name• Table with paper-title, date, author-ID• Print out paper-title, author-full-name• Normalized: author changes name, only gets

changed once• Beware Social Security Numbers!

Who cares about databases?

• Software Engineering deals with large-scale systems

• Virtually all large-scale systems have a database component

• Often the centerpiece of a system– And an organization

• Also, DBAs have the highest salaries in the IT field

• Hey, look at Larry Ellison

Remember IMS?

• Remind you of anything?• Anything else?• Everything comes back in style• We all thought IMS was dead, right?

– IMS serves 200 million end users, managing over 15 billion Gigabytes of production data and processing over 50 billion transactions every day.

– One customer reports 3000 days uptime– Legacy code really is out there

Future of databases?

• Object-oriented DBMS’s (OODBMS)– Why not just store objects in a database?

– Persistent stores

– Numerous companies out there doing this

– Java can serialize to a database as well

• Combine: Object-Relational DBMS (ORDBMS)– Relational model good for joins, etc., more so than

object-oriented models

• Take the Advanced DB class…

Languages

• Easily too much to cover in ~ two classes• We’ll focus on the fundamental differences

between Java and C/C++• Give you a start for later courses• Big hint: HW4 will probably include a small C/C+

+ program• Really don’t have time to cover Perl, Python, etc.• Eventual goal: you should be able to abstract the

language away

Hello, World in C

#include <stdio.h>int main(void) {

printf(“Hello, world!”);

}

• OK, how much of the above is C, the language?

• cpp, libc

Compiling

• gcc hello.c– “GNU C Compiler”

• Output: a.out– Uh…– gcc –o hello hello.c

C compilers are stupid (or simple)

• C compilers cannot auto-compile dependencies• Couldn’t find run-time libraries• #include is precisely literal• Compiles to native code

– No interpreter! Very fast and small!– No garbage collection

• Compiles top-down: need prototypes• Linking: “object code” statically or dynamically

linked to each other in special process

C for the Java programmer

• Java “ripped off” C– Java widely considered “C with classes”– More like C than C++

• for/while, if-then-else, switch (broken) all adopted perfectly from C

• Operators, ++/--, etc.• Functions very similar to methods• But no objects!

C’s data types

• Similar to Java’s lower-case types– char, int, short, long, single, double– no boolean – use 0 or 1

• Common practice: #define TRUE 1

• C is not strongly typed– int i = ‘c’;– As a matter of fact, chars are just bytes

• Different structures have different sizes• Formal mechanism for references: pointers

– Address of structure in machine’s memory!

What does this mean for you?

• AWT/Swing: Client people will need this• CVE’s: If you’re interested in research,

otherwise not a whole lot• Databases: You’ll probably want to take

this class– Deals with database usage and designing the

backend

• C: you’ll need to know sooner or later