Projects/Nepomuk: Difference between revisions

Latest revision as of 06:44, 16 November 2023

Warning

The Nepomuk project no longer exists in modern day KDE software. From KDE Applications 4.13 onwards, the ' Baloo' file indexing and file search framework replaces Nepomuk. Read details on the changes for Applications 4.13 here.

About Nepomuk

Nepomuk serves as a cross application semantic storage backend. It aims at collecting data from various sources - file indexing, the web, applications, etc, and linking them all together to form a cohesive map of data.

This page is dedicated to third party documentation for Nepomuk. To know more about Nepomuk from a user's point of view, head over to the Nepomuk page on UserBase. Or to know more about the Nepomuk community and getting involved in Nepomuk, head over to the Nepomuk Community Page.

Documentation

Any new project is intimidating and jumping right into the API Documentation can be scary. So, we have prepared some articles which explain the different aspects of Nepomuk and even touch on some advanced features.

The documentation of any project is always in progress as the code base is always evolving. If you feel that the documentation is lacking in some regard, please come talk to us. We'd love to hear your feedback, and the documentation might just get improved in the process.

Nepomuk Mailing List: [email protected]
IRC Channel: #nepomuk-kde on freenode

Introductory Material

If you're just getting started with Nepomuk and want to know a quick way to fetch some data.

Managing Data

This section includes more in-depth articles on how manage the data in Nepomuk. As a starting point you should probably open up the Nepomuk API Documentation. It is generally more up to date than the articles mentioned below.

File Indexing

With 4.10, the file indexing architecture has substantially changed. We no longer rely on strigi, and have our own plugin based interface.

Writing an Indexing Plugin

Querying

As you advance into Nepomuk, you'll want to move beyond just fetching and pushing data and will want to query Nepomuk for specialized data. One can query Nepomuk in many different ways, the important part is to optimize your queries and make sure they run well on production systems where the database sizes may way very large.

Architectural Overview

If you're looking to get more involved with Nepomuk development process, you should probably need to need to figure out our basic architecture and where you can find all the relevant code.

Nepomuk Internals

When you decide to dig even deeper.

Miscellaneous

Outdated links

The following links provide good reads for getting used to the Nepomuk system and its APIs. <br\> They are slightly outdated, but still has some useful material.

@@ Line 1: / Line 1: @@
 [[Image:Nepomuk_logo_big.png|center|300px]]
+''{{Warning|The Nepomuk project no longer exists in modern day KDE software. From KDE Applications 4.13 onwards, the '[[community:Baloo | Baloo]]' file indexing and file search framework replaces Nepomuk. Read [http://dot.kde.org/2014/02/24/kdes-next-generation-semantic-search details on the changes for Applications 4.13 here].}}
 == About Nepomuk ==
-This page is dedicated to Nepomuk development ideas, progress, experiments, and is a general starting point for new developers.
+'''Nepomuk''' serves as a cross application semantic storage backend. It aims at collecting data from various sources - file indexing, the web, applications, etc, and linking them all together to form a cohesive map of data.
-For general information about the Nepomuk project see the [http://nepomuk.kde.org/ dedicated Nepomuk homepage].
-== Developer Coordination ==
-The Nepomuk project is maintained by [mailto:[email protected] Sebastian Trueg] of Mandriva.
+This page is dedicated to third party documentation for '''Nepomuk'''. To know more about '''Nepomuk''' from a user's point of view, head over to the [http://userbase.kde.org/Special:myLanguage/Nepomuk Nepomuk page on UserBase]. Or to know more about the Nepomuk community and getting involved in '''Nepomuk''', head over to the [http://community.kde.org/Projects/Nepomuk Nepomuk Community Page].
 == Documentation ==
-The following links provide good reads for getting used to the Nepomuk system and its APIs.
+Any new project is intimidating and jumping right into the [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/index.html API Documentation] can be scary. So, we have prepared some articles which explain the different aspects of '''Nepomuk''' and even touch on some advanced features.
-* [[Development/Tutorials/Metadata/Nepomuk|Development Tutorials]]
-* [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk/html/index.html Nepomuk API Documentation]
-* [http://soprano.sourceforge.net/apidox/trunk/index.html Soprano (RDF storage) API]
-== ToDo ==
-Nepomuk is a rather young project with a notorious shortage in developers. There are many tasks and subprojects to get ones hands dirty on. Unlike other projects like Plasma, however, developing for Nepomuk is not easy. One has to read up on a lot of things and fight some day-to-day annoyances. But: helping with the development will improve the situation in any case.
-If you are interested in working on a task in this list, please contact [mailto:[email protected] Sebastian Trueg].
-=== Low level Nepomuk Development Tasks ===
-The low-level development tasks are those that are not directly reflected in the GUI or even in the API used by most developers. However, they are important in terms of performance, scalability, and compatibility.
-==== Soprano Transaction Support ====
-[http://soprano.sf.net/ Soprano] is the RDF database framework used in Nepomuk. Currently Soprano does not support transactions, i.e. sets of commands that can be rolled back. An [http://websvn.kde.org/branches/soprano/experimental experimental development] branch exists which already contains new API for transaction support (while keeping BC).
-It still misses an implementation of the transaction support in Soprano backends (Sesame2 and Virtuoso) and in the client/server architecture.
-=== General Nepomuk ===
-==== Catching all file moves ====
-Nepomuk uses an RDF database for all data. This includes file metadata. Files are referenced by URL. The problem with this is that when a file is moved or renamed we have to realize this and update the metadata accordingly (update the URL in the database).
-For KIO this is fairly simple since we have {{class|KDirNotify}}. The [http://techbase.kde.org/Development/Tutorials/Metadata/Nepomuk/FileWatchService Nepomuk filewatch service] takes care of this and updates the metadata whenever KIO moves or deletes a file.
-However, if a file is moved by a non-KDE application (typical example: the shell via the mv command) the filewatch service does not notice it and the file -> metadata link is gone. This is a bad situation which sadly cannot be solved easily. Systems like inotify are too restricted.
+The documentation of any project is always in progress as the code base is always evolving. If you feel that the documentation is lacking in some regard, please come talk to us. We'd love to hear your feedback, and the documentation might just get improved in the process.
-Thus, while having a more powerful replacement for inotify would be great, in the meantime we should work with what we got.
+'''Nepomuk Mailing List: ''' nepomuk@kde.org <br/>
+'''IRC Channel:''' #nepomuk-kde on freenode
-The idea is to create a [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk/html/classNepomuk_1_1Service.html Nepomuk service] that tries very hard to find file moves. It would regularly check the database for dangling metadata and then try to find the file using all kinds of evidence:
+=== Introductory Material ===
-* file name matching
+If you're just getting started with '''Nepomuk''' and want to know a quick way to fetch some data.
-* xattrs if available (this would mean that Nepomuk::Resource also needs to set the xattrs at some point)
-* checksums, maybe the checksum of the first N bytes or something like that to speed the process up
-* compare metadata extracted by strigi
-* etc.
-All this information should be used to generate a score which indicates the certainty of the file matching. Then the final decision would have to be made by the user.
+* [[Special:myLanguage/Projects/Nepomuk/QuickStart| Quick Start]]
+* [[Special:myLanguage/Projects/Nepomuk/OntologyBasics| Basic Ontology concepts]]
+* [[Special:myLanguage/Projects/Nepomuk/Uris| Questions about URIs]]
-'''''Hints:'''''
+=== Managing Data ===
-* Try to detect if a complete folder has been moved (or deleted) and do not ask the user for every single file.
-==== Handling of external storage ====
+This section includes more in-depth articles on how manage the data in '''Nepomuk'''. As a starting point you should probably open up the [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk-core/html/index.html Nepomuk API Documentation]. It is generally more up to date than the articles mentioned below.
-A typical problem with the way Nepomuk handles files and file metadata are removable storage devices. They can be mounted at different paths on different systems. But still one wants to keep the metadata stored in Nepomuk.
+* [[Special:myLanguage/Projects/Nepomuk/Resources| Using Resources]]
-If possible one would even want to be able to search for files saved on an USB stick even if it is not plugged in.
+* [[Special:myLanguage/Projects/Nepomuk/ResourceWatcher| Monitoring Changes]]
+* [[Special:myLanguage/Projects/Nepomuk/BulkChanges| Bulk Changes]]
+* [[Special:myLanguage/Projects/Nepomuk/DataFeeders| Data Feeders]]
-The [http://trueg.wordpress.com/2009/04/15/portable-meta-information-yet-again-only-this-time-there-is-code/ blog entry about removable storage in Nepomuk] already discusses this problem and shows some existing code in KDE's [http://websvn.kde.org/trunk/playground/base/removablestorageservice/ playground] which tries to tackle this problem.
+=== File Indexing ===
-However, one actually needs more. The system would have to be embedded into KIO to make sure the metadata cache on the removable storage device is always up-to-date. Also it is directly related to the problem of relative vs. absolute file URLs.
+With 4.10, the file indexing architecture has substantially changed. We no longer rely on strigi, and have our own plugin based interface.
-==== Relative vs. Absolute File URLs ====
+* [[Special:myLanguage/Projects/Nepomuk/IndexingPlugin| Writing an Indexing Plugin]]
-Currently Nepomuk uses the absolute file URLs as URI identifiers for the resources representing the files in the Nepomuk RDF store. The file ''~/test.png'' for example has the resource URI ''file:///home/<username>/test.png''. This is nice in many situations since one can simply use the file URL to query file metadata but on the other hand we need to change a lot of triples whenever the file is moved (not to mention the removable storage problem above).
+=== Querying ===
-Thus, the idea is to use random URI identifiers for new file resources and store the file path relative to the mount point. This would solve the above problem with removable devices and make updates after file moves simpler (only update the path).
+As you advance into '''Nepomuk''', you'll want to move beyond just fetching and pushing data and will want to query '''Nepomuk''' for specialized data. One can query '''Nepomuk''' in many different ways, the important part is to optimize your queries and make sure they run well on production systems where the database sizes may way very large.
-This problem should probably be tackled by introducing a class Nepomuk::File as a subclass to ''[http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk/html/classNepomuk_1_1Resource.html Nepomuk::Resource]'' which handles all these special file stuff like making sure we have a correct nao:filePath property and so on (currently all that is done with an ''if'' clause in ''Nepomuk::Resource''.
+* [[Special:myLanguage/Projects/Nepomuk/QueryingMethods| Different ways to Query Nepomuk]]
+* [[Special:myLanguage/Projects/Nepomuk/QueryLibrary| Nepomuk Query Library]]
+* [[Special:myLanguage/Projects/Nepomuk/SparqlQueries| Sparql Queries]]
-=== GUI ===
+=== Architectural Overview ===
-==== Better tagging widget ====
+If you're looking to get more involved with '''Nepomuk''' development process, you should probably need to need to figure out our basic architecture and where you can find all the relevant code.
-Currently there is a [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk/html/classNepomuk_1_1TagWidget.html tagging widget in kdelibs] which is pretty ugly and not even used. Then there is the tag cloud used in Dolphin. The latter was already criticized for not being appropriate in that situation.
+* [[Special:myLanguage/Projects/Nepomuk/Repositories| Nepomuk Repositories]]
+* [[Special:myLanguage/Projects/Nepomuk/ComponentOverview| Nepomuk Architectural Overview]]
+* [[Special:myLanguage/Projects/Nepomuk/kioslaves| Nepomuk KIO Slaves]]
-Thus, it would be great to make [http://api.kde.org/4.x-api/kdelibs-apidocs/nepomuk/html/classNepomuk_1_1TagWidget.html Nepomuk::TagWidget] a nice and usable (maybe talk to the usability people) widget that can then be used in Dolphin, Gwenview, and pretty much any application that wants to tag resources.
+=== Nepomuk Internals ===
-== Ideas ==
+When you decide to dig even deeper.
-There are many ideas on how to improve the Nepomuk system or on how to use it. This is the place to list them all.
+* [[Special:myLanguage/Projects/Nepomuk/GraphConcepts| Graph handling]]
+* [[Special:myLanguage/Projects/Nepomuk/VirtuosoInternal| Virtuoso Internals]]
+* [[Special:myLanguage/Projects/Nepomuk/OntologyExtention| Extending the Ontologies]]
-Feel free to add your own ideas. Please leave your name in case someone wants to contact you for details or a discussion of the idea.
+=== Miscellaneous ===
-=== Remember download locations ===
+* [[Special:myLanguage/Projects/Nepomuk/Nepomuk2Port| Porting to Nepomuk2]]
+* [[Special:myLanguage/Projects/Nepomuk/ManagingNepomukProcesses| Managing Nepomuk Processes]]
+* [[Special:myLanguage/Projects/Nepomuk/TestEnvironment| Nepomuk Test Environment]]
+* [[Special:myLanguage/Development/Tutorials/Metadata/Nepomuk/TipsAndTricks| Nepomuk Tips and Tricks]]
+* [[Special:myLanguage/Projects/Nepomuk/NepomukShow| Debugging Nepomuk Data]]
-As [http://www.kdedevelopers.org/node/3843 blogged before] remembering the download location and the referrer web page is a pretty good idea. The most pressing problem at the moment is finishing [http://dev.nepomuk.semanticdesktop.org/wiki/NdoOntology the download ontology].
+==== Outdated links ====
+The following links provide good reads for getting used to the '''Nepomuk''' system and its APIs. <br\>
+They are slightly outdated, but still has some useful material.
+* [[Special:myLanguage/Development/Tutorials/Metadata/Nepomuk|Development Tutorials]]
+* [[Special:myLanguage/Projects/Nepomuk/Ideas|Random Ideas]]
+* [[Special:myLanguage/Projects/Nepomuk/Qualified_Relations_Idea| Qualified Relations Idea]]
+* [[Special:myLanguage/Projects/Nepomuk/ScenarioExamples| Scenario Examples]]
-=== FIXME: add ideas ===
+[[Category:Documentation]]