TagFS — Tag Semantics for Hierarchical File Systems

TagFS — Tag Semantics for Hierarchical File Systems Bonus Track: Introducing SemFS 2006 2006 Web3.0 2006 Stephan Bloehdorn Institute AIFB, University of Karlsruhe, Germany Olaf Görlitz ISWeb, University of Koblenz-Landau, Germany Simon Schenk ISWeb, University of Koblenz-Landau, Germany Max Völkel Forschungszentrum Informatik, Karlsruhe, Germany talk Max Völkel Forschungszentrum Informatik, Karlsruhe, Germany

Motivation
„ Every user [...] indicated that their attempts to establish elaborate filing schemas for archived information failed because they proved to require more time and effort than the information was worth.“ Barreau and Nardi, 1995
Contributions
Mapping file system semantics to tagging semantics
Architecture for a semantic file system

Hierarchical file systems have some problems
Single locaction property
E.g. where to put a song produced by two artists?
Each file may be only in one folder
There are links/shortcuts, but where to put the „primary“ file?
Browsing to maximum specifity
E.g. 5 clicks for /My Music/Fatboy Slim/2006/danceable/favourite even if there are only 5 Fatboy Slim songs altogether
The more you organise, the more you have to browse
Missing orthogonality
E.g. /2003/Fatboy Slim/favourite or /favourite/Fatboy Slim/2003 ?
Many dimensions, only one access path
No query refinement
FS lists only directories explicitly placed there, no help

Tagging
Simple idea:
Instead of putting resources in folders (nested containers), put tags (labels) on resources
Tagging user interfaces
User sees a resource, can type in tags (simple, single keywords, separated by space or comma)
User can click on a tag, UI lists all resources with that tag assigned
Conjunctive queries: e.g. fatboyslim+favourite
Examples: del.icou.us, flickr, 100 more
Who has used a tagging system?
new Web2.0

Example: del.icio.us Tagging Browsing Queries

Comparison
File system: partition of the adress space
Tagging: overlapping sets
a b a+b+c a+c b+c a+b c a b c /a /a/b /a/c /a /a/b /a/b/c /a/c /a/c/b /c /c/b /c/b/a /c/a /c/a/b /b /b/a /b/a/c /b/c /b/c/a

Mapping file system semantics to tagging semantics Query and Browse – the easy parts
Query
Use path as query, e.g. /a/b/c = query for a + b + c
Browsing / a
Contained files: all resources tagged with a (  if not to many)
Contained folders: All tags b , for which the conjunctive query a+b is not empty
Any tag is a good starting point!
Note: Virtual directory views are computed at runtime

Mapping file system semantics to tagging semantics Tagging – the hard part
Changing existing tagging
Copy file from a to b = tag file with b also
Move file from a to b = remove tag a , add tag b
Delete file from a = remove tag a
Rename a to b = for all files tagged with a : remove a , add b
Add files to TagFS
Add file to folder a = add file to TagFS; tag file with a
 File identity determined by hash or filename  Allows updating a file, if content is changed externally
Delete files from TagFS
 Move file to deleteMe = delete file
Create tag a = create folder a
 This folder would not be shown, because it‘s empty

Tagging in the file system
Many locaction property
Each file may carry as many tags as desired
Browsing until result is small enough
Each folder contains all files tagged with the folder name
Orthogonality of information dimensions
Path interpreted as a conjunctive query, e.g. Lisa Ekdahl/2006 is the same as 2006/Lisa Ekdahl
Not all reviewers agreed on this 
Query refinement
Each folder lists useful query refinements as sub-folers
Providing all standard filesystem operations
 compatibility with existing applications

Introducing SemFS
Implementing TagFS with SemFS
Web2.0 Web3.0 Semantic Desktop RDF keywords Bonus Track

What is a file system?

What is a file system? Organising files … An address given as path expression := Letter “ : “ ( “ “ name)* File System dir! response files folders name metadata metadata

What is a file system? … managing binary data File System metadata data 1011 write 1011 read 1011

What is a file system? … managing binary data File System rename metadata data

What is a file system? … managing binary data File System Add file or delete file metadata data

What is a file system? Organising files and managing binary data
View( path )  Metadata-Table
Contained files,
Contained directories,
Metadata: getName, getDate, …
Binary content irrelevant
Update
Metadata: setName, setDate, add file, delete file, move file
Binary+Metadata: read file, write file, trunc file

What is a virtual file system? Organising files and managing binary data op Virtual File System Looks and behaves like a file system… … but is no file system. It‘s implemen-ted differently. metadata data X Flickr CMS File System metadata data

What is a semantic file system? Organising files and managing binary data. op Semantic File System Flexible implementation. Unified metadata  unified search metadata data X Flickr CMS File System

Architecture of SemFS: Filters
Input: Frontend gets path
SemFS maintains a list of filters ,
Formal: Filter(graph, path)  (filtered graph, shorter path)
Each filter is asked sequencially to process a path
A filter consumes some parts of a path, and returns a filtered metadata graph
Filter can delegate to a particular filter or delegate back to filter chain
Output: Finally the filtered metadata graph is transformed to a directory view

Architecture of SemFS: Example for Filters
Filter-List: [Favourite, Artist , Main]
Main-Filter processes “My Music“ and returns filtered graph, containing all music-resources. Delegates to Artist-Filter.
Artist-Filter processes “Fatboy Slim“ and returns all resource, that have e.g. the dc:creator „Fatboy Slim“. Delegates to filter chain.
Favourites-Filter processes “favourite“ and returns all resources accesses more than n times in the last x days
Main Artist Favourite My MusicFatboy Slimfavourite Fatboy Slimfavourite favourite

Architecture of SemFS: Example for Filters
Filter-List: [Favourite, Artist , Main]
Main-Filter processes “My Music“ and returns filtered graph, containing all music-resources. Delegates to Artist-Filter.
Artist-Filter processes “Fatboy Slim“ and returns all resource, that have the rdfs:label „Fatboy Slim“. Delegates to filter chain.
Favourites-Filter processes “favourite“ and returns all resources accesses more than n times in the last x days
Main Artist Favourite My MusicFatboy Slimfavourite Fatboy Slimfavourite favourite
View( path )  Metadata-Table
Contained files,
Contained directories,

Architecture of SemFS: Class-Handlers
Different content-types have different meta-data and different ways to read/write
E.g. local bookmarks, remote bookmarks, images, mp3 files, …
Idea: access each class of content types via a Class-Handler
Can be cached in metadata graph
Updates
Metadata: setName, setDate, add file, delete file, move file
Binary+Metadata: read file, write file, trunc file
Other metadata operations, e.g. setGenre in ID3-tags

Architecture of SemFS: Summary: Metadata Graph, Filters, Class-Handlers
Metadata graph (RDF)
Holds all metadata
acts as a unifying cache, when content has ist own metadata
Filters
Create the view, organise resources (not limited to files)
Class Handlers
Handle different content types and manages binary data

Using SemFS: A tagging file system (TagFS)
One Filter: Tag-Filter
Consumes a single path segment a
Contained files: Returns all resources tagged with a
Contained folders: All tags b , for which the conjunctive query a+b is not empty
One Class Handler
Delegates classic metadata queries to underlying file store
Binary content resides in a folder of a classic file system
Tag-queries handled by metadata graph
New problems
 No two files may have the same name (when rendered)
Rename at insertion or display time

Conclusions
TagFS
Many locaction property
Browsing only until result is small enough, no further
Orthogonality of information dimensions
Query refinement
Compatible with existing applications
SemFS
An efficient way to implement virtual file systems with pluggable semantics
Allows rapid and solid prototype creation
Interoperability with Semantic Desktop applications
Download Prototype at http://isweb.uni-koblenz.de/Research (Linux only, WebDAV/Windows in progress) Thank you. Questions?

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Contact Information
Max Völkel (author, presenter)
Forschungszentrum Informatik, Karlsruhe, Germany
http://www.fzi.de
Stephan Bloehdorn (author)
Institute AIFB, University of Karlsruhe, Germany
http://aifb.uni-karlsruhe.de /
Olaf Görlitz (author) and Simon Schenk (author)
ISWeb, University of Koblenz-Landau, Germany
http://isweb.uni-koblenz.de /

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TagFS — Tag Semantics for Hierarchical File Systems

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TagFS — Tag Semantics for Hierarchical File Systems — Presentation Transcript