1. Section 9 Tagged File Support Design

2. Overview
Background
Project

3. In your hard disk, How many files? How many types of files?
How do you organize them?
Brainstorming

4. Some numbers From a computer at “a” CSE grad’s home Early 1980’s
files
7234 directories
over 600 file types
Early 1980’s
5.25” 2DD disk
360KB
Can’t store those file names!

5. # of data files
Here goes some statistics of my PC

6. # of files Explosion of # of files How do you find what you want? Why?
Hold on… except desktop search! 
Explosion of # of files
space is cheap now
the amount of information generated per people grows quickly.
File is a typical unit of information
Find what you want
Information retrieval: database, search engine, …
most naïve way is keep them in an organized directories and file names

7. Average data file size

8. Characteristics of files
Think about following classes of files
Pure text
Image
Audio
Video
From the perspective of
content
Access pattern
You and Programs
Think about some natural characteristics of certain type of files
pure text: may not exceed 100K usually
image: 1MB for reasonable quality?
audio: 4-5MB for 4min long song
video: 10MB/min?
256 chars: a limit in linux file name which represent the content

9. Complexity of finding information
How do you search
text?
image?
audio?
video?
Can you describe the content in 256 chars?

10. Directory & file names The most naïve approach
Better than monolithic model
Encode information along the path
C:\PICTURES\ – CSE451\PIC00489.JPG
A picture taken during the cse451 section
C:\MUSIC\Anime\OST\Ghost in the Shell – Stand Alone Complex OST\Disc1\01.mp3
A music of track 1 of disc1 in animation ‘Ghost in the Shell – Stand Alone Complex’ OST album
Give real examples how the naïve approach fails to work
Can you tell who or what are shown in that file?
Can you tell the genre or artist from it?

11. Problem Name is not enough! In reality, How can you address this?
Suppose to be unique and used to refer an object
Does not describe the object
Just a unique attribute among others
In reality,
Often wants to find a file by describing contents
Play every Beethoven
Find PPT files used in CSE451 section during spring 2006 …
How can you address this?

12. Extreme case Does user know about file name?
Where does the information come from?
How does it maintain the information?
Is it convenient?

13. Keep meta information: TAG
Maintain meta information of files
Owner, group, permission, timestamps, …
Office documents, PDF: document properties
People start to TAG everything
Tag: Keywords which describe the attribute of contents
Help locate the information
Example
EXIF: for image files
ID3: for mp3 files
Vorbis comments: for Ogg files
Flickr.com, Facebook.com: tag image
Youtube.com, Google video: tag video

14. Question?

15. Project Design supports to manage audio files
Easy to find wanted files
Easy to manage tags
Transparent to underlying tag formats
Support mp3, ogg, wav, …
Reasonable performance
For the players & other programs
Refer project description for more detail

16. Design factors Supporting layer Transition cost Performance
None
Library
Shell
File system
Transition cost
Backward compatibility to tag aware program
Impact on other programs
Performance
Overhead of additional functionalities
Implementation cost
Amount of efforts
Layer: order of specific to general
Existing tag aware programs should work

17. Reminder There is no perfect solution Present concrete examples
Don’t worry about the correctness
Present concrete examples
E.g, new system call, searching wanted files, …
Justify your design decision
Give rational about why it has to be

18. Related topics From Apple From Microsoft From Google Resource fork
Spotlight
From Microsoft
WinFS
From Google
Google desktop search