README
------
-Laconica 0.6.4 ("Catapult")
-11 December 2008
+Laconica 0.7.2 ("Talk about the Passion")
+11 March 2009
This is the README file for Laconica, the Open Source microblogging
platform. It includes installation instructions, descriptions of
group to exchange short (140 character) messages over the Web. Users
can choose which people to "follow" and receive only their friends' or
colleagues' status messages. It provides a similar service to sites
-like Twitter, Jaiku, Pownce and Plurk.
+like Twitter, Jaiku and Plurk.
With a little work, status messages can be sent to mobile phones,
instant messenger programs (GTalk/Jabber), and specially-designed
desktop clients that support the Twitter API.
Laconica supports an open standard called OpenMicroBlogging
-(http://openmicroblogging.org/) that lets users on different Web sites
+<http://openmicroblogging.org/> that lets users on different Web sites
or in different companies subscribe to each others' notices. It
enables a distributed social network spread all across the Web.
Laconica was originally developed for the Open Software Service,
-Identi.ca (http://identi.ca/). It is shared with you in hope that you
+Identi.ca <http://identi.ca/>. It is shared with you in hope that you
too make an Open Software Service available to your users. To learn
-more, please see the Open Software Service Definition 1.0:
+more, please see the Open Software Service Definition 1.1:
- http://www.openknowledge.org/ossd
+ http://www.opendefinition.org/ossd
License
=======
New this version
================
-This is a minor feature and security improvement version from version
-0.6.3 (release 24 Nov 2008). Notable features of version 0.6.4 include:
-
-- "private" installs won't show any data to the outside world; redirect
- non-logged-in users to login. (See "Private" below)
-- Ability to "block" a subscriber, which forces them to unsubscribe,
- doesn't allow them to subscribe again, and doesn't allow them to send
- @-replies
-- Fine-grained control of subscriptions; users can choose not to receive
- notices from other users over SMS, or IM, or both
-- support for Mozilla microsummaries
- (https://wiki.mozilla.org/Microsummaries)
-- more efficient support for blacklisting users from the public page
-- instructions on the public page for people who aren't logged in
-- better registration instructions
-- a check for license compatibility in receiving OMB notices
-- HTML output in RSS 1.0, 2.0, and Atom feeds
-- tuned and more reliable 'rememberme' cookies for username/password
- and OpenID logins
-- a utility for setting user passwords
-- a "ban" configuration variable to ban certain users from posting
- notices
-- an configurable posting throttle to keep any one user from flooding
- the site with messages.
-- fine-tuned url-shortening: only shorten if it's needed, only expand
- certain URLs, and handle failure of URL-shortening services reliably
-- disable Ajax input for notices, subscribe, nudge, while the
- request is processing
-- early implementation of support for Last-Modified and ETag-based
- caching
-- initial microformats support
-- redirect on bad nicknames in URLs
-- correctly send emails in recipient's, not sender's, language
-- correct email content type
-- Change "Most Favorited" page to "Popular"
-- properly support the "since" parameter in API calls
-- Fix for changes in validate_credentials API call for the Twitter
- bridge
-- Fix for fatal error when sending email confirmation on registration
-- Better replies for commands sent through the Ajax channel
-- Add a User-Agent string for OMB requests
-- Upgrade upstream library XMPPHP
-- Upgrade upstream library JQuery Forms
-- Code cleanup: checkboxes have proper <label> elements
-- Code cleanup: consolidated various notice-listing code in one place
-- Better support for unsubscribing from a remote user
-- Stump of experimental Facebook application (not ready for use! code
- review only!)
-- Stump of experimental user account deletion (not ready for use! code
- review only!)
+This is a minor bug-fix and feature release since version 0.7.1,
+released Feb 9 2009. Notable changes this version:
+
+- First version of a web-based installer
+- Use Net_URL_Mapper instead of mod_rewrite to map "fancy URLs",
+ for a much simpler installation and use of PATH_INFO on sites
+ that don't have mod_rewrite.
+- A plugin framework for system events, to make it easier to build
+ server-side plugins.
+- A plugin for Google Analytics
+- A plugin to use blogspam.net to check notices for spam
+- A plugin to send linkbacks for notices about blog posts
+- Configurable check for duplicate notices in a specific time
+ period
+- Better Atom feeds
+- First implementation of Twitter Search API
+- Add streamlined mobile device-friendly styles when enabled in config.
+- A queue server for sending notices to Twitter
+- A queue server for sending notices to Facebook
+- A queue server for sending notices to a ping server
+- Fixed a bug in nonces for OAuth in OpenMicroBlogging
+- Fixed bugs in transfer of avatars in OpenMicroBlogging
+- @-links go to permalinks for local users
+- Better handling of DB errors (instead of dreaded DB_DataObject blank
+ screen)
+- Initial version of an RPM spec file
+- More consistent display of notices in notice search
+- A stylesheet for printed output
+- "Social graph" methods for Twitter API
+- Documentation for the JavaScript badge
+- Debugged a ton of problems that happened with E_NOTICE on
+- Better caching in RSS feeds
+- Optionally send email when an @-message is received
+- Automatically add tags for every group message
+- Add framebusting JavaScript to help avoid clickjacking attacks.
+- Optionally ignore some notice sources for public page.
+- Add default SMS carriers and notice sources to distribution file.
+- Change titles to use mixed case instead of all uppercase.
+- Use exceptions for error handling.
+
+Changes in version 0.7.1:
+
+- Vast improvement in auto-linking to URLs.
+- Link to group search from user's group page
+- Improved interface in Facebook application
+- Fix bad redirects in delete notice
+- Updated PostgreSQL database creation script
+- Show filesize in avatar/logo upload
+- Vastly improved avatar/logo upload
+- Allow re-authentication with OpenID
+- Correctly link hashtabs inside parens and brackets
+- Group and avatar image transparency works
+- Better handling of commands through the Web and Ajax channels
+- Fix links for profile page feeds
+- Fixed destroy method in API
+- Fix endpoint of Connect menu when XMPP disabled
+- Show number of group members
+- Enable configuration files in /etc/laconica/
+
+Changes in version 0.7.0:
+
+- Support for groups. Users can join groups and send themed notices
+ to those groups. All other members of the group receive the notices.
+- Laconica-specific extensions to the Twitter API.
+- A Facebook application.
+- A massive UI redesign. The HTML generated by Laconica has changed
+ significantly, to make theming easier and to give a more open look
+ by default. Also, sidebar.
+- Massive code hygiene changes to move towards compliance with the PEAR
+ coding standards and to support the new UI redesign.
+- Began the breakup of util.php -- moved about 30% of code to a views
+ hierarchy.
+- UI elements for statistical information (like top posters or most
+ popular groups) added in a sidebar.
+- include Javascript badge by Kent Brewster.
+- Updated online documentation.
+- Cropping of user avatars using Jcrop.
+- fix for Twitter bridge to not send "Expect:" headers.
+- add 'dm' as a synonym for 'd' in commands.
+- Upgrade upstream version of jQuery to 1.3.
+- Upgrade upstream version of PHP-OpenID to 2.1.2.
+- Move OpenMicroBlogging specification to its own repository.
+- Make tag-based RSS streams work.
+- Additional locales: Bulgarian, Catalan, Greek, Hebrew, simplified
+ Chinese, Telugu, Taiwanese Chinese, Vietnamese,
+- PostgreSQL updates.
+- Nasty bug in Twitter bridge that wouldn't verify with Twitter
Prerequisites
=============
version (patches have been submitted). Upgrading to the upstream
version may render your Laconica site unable to send or receive XMPP
messages.
+- Facebook library. Used for the Facebook application.
+- PEAR Services_oEmbed. Used for some multimedia integration.
+- PEAR HTTP_Request is an oEmbed dependency.
+- PEAR Validat is an oEmbed dependency.e
+- PEAR Net_URL is an oEmbed dependency.2
A design goal of Laconica is that the basic Web functionality should
work on even the most restrictive commercial hosting services.
1. Unpack the tarball you downloaded on your Web server. Usually a
command like this will work:
- tar zxf laconica-0.6.4.tar.gz
+ tar zxf laconica-0.7.1.tar.gz
- ...which will make a laconica-0.6.4 subdirectory in your current
+ ...which will make a laconica-0.7.1 subdirectory in your current
directory. (If you don't have shell access on your Web server, you
may have to unpack the tarball on your local computer and FTP the
files to the server.)
2. Move the tarball to a directory of your choosing in your Web root
directory. Usually something like this will work:
- mv laconica-0.6.4 /var/www/mublog
+ mv laconica-0.7.1 /var/www/mublog
This will make your Laconica instance available in the mublog path of
your server, like "http://example.net/mublog". "microblog" or
configure virtual hosts on your web server, you can try setting up
"http://micro.example.net/" or the like.
-3. You should also take this moment to make your avatar subdirectory
- writeable by the Web server. An insecure way to do this is:
+3. Make your target directory writeable by the Web server.
- chmod a+w /var/www/mublog/avatar
+ chmod a+w /var/www/mublog/
On some systems, this will probably work:
- chgrp www-data /var/www/mublog/avatar
- chmod g+w /var/www/mublog/avatar
+ chgrp www-data /var/www/mublog/
+ chmod g+w /var/www/mublog/
If your Web server runs as another user besides "www-data", try
that user's default group instead. As a last resort, you can create
- a new group like "avatar" and add the Web server's user to the group.
+ a new group like "mublog" and add the Web server's user to the group.
+
+4. You should also take this moment to make your avatar subdirectory
+ writeable by the Web server. An insecure way to do this is:
+
+ chmod a+w /var/www/mublog/avatar
+
+ You can also make the avatar directory writeable by the Web server
+ group, as noted above.
-4. Create a database to hold your microblog data. Something like this
+5. Create a database to hold your microblog data. Something like this
should work:
mysqladmin -u "username" --password="password" create laconica
a tool like PHPAdmin to create a database. Check your hosting
service's documentation for how to create a new MySQL database.)
-5. Run the laconica.sql SQL script in the db subdirectory to create
- the database tables in the database. A typical system would work
- like this:
-
- mysql -u "username" --password="password" laconica < /var/www/mublog/db/laconica.sql
-
- You may want to test by logging into the database and checking that
- the tables were created. Here's an example:
-
- SHOW TABLES;
-
6. Create a new database account that Laconica will use to access the
database. If you have shell access, this will probably work from the
MySQL shell:
- GRANT SELECT,INSERT,DELETE,UPDATE on laconica.*
+ GRANT ALL on laconica.*
TO 'lacuser'@'localhost'
IDENTIFIED BY 'lacpassword';
You should change 'lacuser' and 'lacpassword' to your preferred new
- username and password. You may want to test logging in as this new
- user and testing that you can SELECT from some of the tables in the
- DB (use SHOW TABLES to see which ones are there).
-
-7. Copy the config.php.sample in the Laconica directory to config.php.
-
-8. Edit config.php to set the basic configuration for your system.
- (See descriptions below for basic config options.) Note that there
- are lots of options and if you try to do them all at once, you will
- have a hard time making sure what's working and what's not. So,
- stick with the basics at first. In particular, customizing the
- 'site' and 'db' settings will almost definitely be needed.
-
-9. At this point, you should be able to navigate in a browser to your
- microblog's main directory and see the "Public Timeline", which
- will be empty. If not, magic has happened! You can now register a
- new user, post some notices, edit your profile, etc. However, you
- may want to wait to do that stuff if you think you can set up
- "fancy URLs" (see below), since some URLs are stored in the database.
+ username and password. You may want to test logging in to MySQL as
+ this new user.
+
+7. In a browser, navigate to the Laconica install script; something like:
+
+ http://yourserver.example.com/mublog/install.php
+
+ Enter the database connection information and your site name. The
+ install program will configure your site and install the initial,
+ almost-empty database.
+
+8. You should now be able to navigate to your microblog's main directory
+ and see the "Public Timeline", which will be empty. If not, magic
+ has happened! You can now register a new user, post some notices,
+ edit your profile, etc. However, you may want to wait to do that stuff
+ if you think you can set up "fancy URLs" (see below), since some
+ URLs are stored in the database.
Fancy URLs
----------
-By default, Laconica will have big long sloppy URLs that are hard for
-people to remember or use. For example, a user's home profile might be
+By default, Laconica will use URLs that include the main PHP program's
+name in them. For example, a user's home profile might be
found at:
- http://example.org/mublog/index.php?action=showstream&nickname=fred
+ http://example.org/mublog/index.php/mublog/fred
+
+On certain systems that don't support this kind of syntax, they'll
+look like this:
+
+ http://example.org/mublog/index.php?p=mublog/fred
It's possible to configure the software so it looks like this instead:
http://example.org/mublog/fred
These "fancy URLs" are more readable and memorable for users. To use
-fancy URLs, you must either have Apache 2.2.x with .htaccess enabled
-and mod_redirect enabled, -OR- know how to configure "url redirection"
-in your server.
+fancy URLs, you must either have Apache 2.x with .htaccess enabled and
+mod_redirect enabled, -OR- know how to configure "url redirection" in
+your server.
1. Copy the htaccess.sample file to .htaccess in your Laconica
directory. Note: if you have control of your server's httpd.conf or
If you changed your HTTP server configuration, you may need to restart
the server first.
-If you have problems with the .htaccess file on versions of Apache
-earlier than 2.2.x, try changing the regular expressions in the
-htaccess.sample file that use "\w" to just use ".".
-
Sphinx
------
Each user sends to a made-up email address, which they keep a secret.
Incoming email that is "From" the user's SMS email address, and "To"
the users' secret email address on the site's domain, will be
-converted to a message and stored in the DB.
+converted to a notice and stored in the DB.
For this to work, there *must* be a domain or sub-domain for which all
(or most) incoming email can pass through the incoming mail filter.
XMPP
----
-XMPP (eXtended Message and Presence Protocol, http://xmpp.org/) is the
+XMPP (eXtended Message and Presence Protocol, <http://xmpp.org/>) is the
instant-messenger protocol that drives Jabber and GTalk IM. You can
distribute messages via XMPP using the system below; however, you
need to run the XMPP incoming daemon to allow incoming messages as
needs as a parameter the install path; if you run it from the
Laconica dir, "." should suffice.
-This will run six (for now) queue handlers:
+This will run eight (for now) queue handlers:
* xmppdaemon.php - listens for new XMPP messages from users and stores
them as notices in the database.
of registered users.
* xmppconfirmhandler.php - sends confirmation messages to registered
users.
+* twitterqueuehandler.php - sends queued notices to Twitter for user
+ who have opted to set up Twitter bridging.
+* facebookqueuehandler.php - sends queued notices to Facebook for users
+ of the built-in Facebook application.
Note that these queue daemons are pretty raw, and need your care. In
particular, they leak memory, and you may want to restart them on a
# Update Twitter friends subscriptions every half hour
0,30 * * * * /path/to/php /path/to/laconica/scripts/synctwitterfriends.php>&/dev/null
+Built-in Facebook Application
+-----------------------------
+
+Laconica's Facebook application allows your users to automatically
+update their Facebook statuses with their latest notices, invite
+their friends to use the app (and thus your site), view their notice
+timelines, and post notices -- all from within Facebook. The application
+is built into Laconica and runs on your host. For automatic Facebook
+status updating to work you will need to enable queuing and run the
+facebookqueuehandler.php daemon (see the "Queues and daemons" section
+above).
+
+Quick setup instructions*:
+
+Install the Facebook Developer application on Facebook:
+
+ http://www.facebook.com/developers/
+
+Use it to create a new application and generate an API key and secret.
+Uncomment the Facebook app section of your config.php and copy in the
+key and secret, e.g.:
+
+ # Config section for the built-in Facebook application
+ $config['facebook']['apikey'] = 'APIKEY';
+ $config['facebook']['secret'] = 'SECRET';
+
+In Facebook's application editor, specify the following URLs for your app:
+
+- Callback URL: http://example.net/mublog/facebook/
+- Post-Remove URL: http://example.net/mublog/facebook/remove
+- Post-Add Redirect URL: http://apps.facebook.com/yourapp/
+- Canvas URL: http://apps.facebook.com/yourapp/
+
+(Replace 'example.net' with your host's URL, 'mublog' with the path
+to your Laconica installation, and 'yourapp' with the name of the
+Facebook application you created.)
+
+Additionally, Choose "Web" for Application type in the Advanced tab.
+In the "Canvas setting" section, choose the "FBML" for Render Method,
+"Smart Size" for IFrame size, and "Full width (760px)" for Canvas Width.
+Everything else can be left with default values.
+
+*For more detailed instructions please see the installation guide on the
+Laconica wiki:
+
+ http://laconi.ca/trac/wiki/FacebookApplication
+
Sitemaps
--------
-Sitemap files (http://sitemaps.org/) are a very nice way of telling
+Sitemap files <http://sitemaps.org/> are a very nice way of telling
search engines and other interested bots what's available on your site
and what's changed recently. You can generate sitemap files for your
Laconica instance.
like './sitemapindex.xml'. sitemap-directory is the directory where
you want the sitemaps stored, like './sitemaps/' (make sure the dir
exists). URL-prefix-for-sitemaps is the full URL for the sitemap dir,
- typically something like 'http://example.net/mublog/sitemaps/'.
+ typically something like <http://example.net/mublog/sitemaps/>.
You can use several methods for submitting your sitemap index to
search engines to get your site indexed. One is to add a line like the
Themes
------
-There are two themes shipped with this version of Laconica: "stoica",
+There are two themes shipped with this version of Laconica: "identica",
which is what the Identi.ca site uses, and "default", which is a good
basis for other sites.
You may want to start by copying the files from the default theme to
your own directory.
+NOTE: the HTML generated by Laconica changed *radically* between
+version 0.6.x and 0.7.x. Older themes will need signification
+modification to use the new output format.
+
Translation
-----------
-Translations in Laconica use the gettext system (http://www.gnu.org/software/gettext/).
+Translations in Laconica use the gettext system <http://www.gnu.org/software/gettext/>.
Theoretically, you can add your own sub-directory to the locale/
subdirectory to add a new language to your system. You'll need to
compile the ".po" files into ".mo" files, however.
Contributions of translation information to Laconica are very easy:
-you can use the Web interface at http://laconi.ca/entrans/ to add one
+you can use the Web interface at http://laconi.ca/pootle/ to add one
or a few or lots of new translations -- or even new languages. You can
also download more up-to-date .po files there, if you so desire.
There is no built-in system for doing backups in Laconica. You can make
backups of a working Laconica system by backing up the database and
-the Web directory. To backup the database use mysqldump (http://ur1.ca/7xo)
+the Web directory. To backup the database use mysqldump <http://ur1.ca/7xo>
and to backup the Web directory, try tar.
Private
=========
If you've been using Laconica 0.6, 0.5 or lower, or if you've been
-tracking the "darcs" version of the software, you will probably want
+tracking the "git" version of the software, you will probably want
to upgrade and keep your existing data. There is no automated upgrade
-procedure in Laconica 0.6.4. Try these step-by-step instructions; read
+procedure in Laconica 0.7.1. Try these step-by-step instructions; read
to the end first before trying them.
0. Download Laconica and set up all the prerequisites as if you were
directory to your new directory.
9. Copy htaccess.sample to .htaccess in the new directory. Change the
RewriteBase to use the correct path.
-10. Rebuild the database. Go to your Laconica directory and run the
- rebuilddb.sh script like this:
-
- ./scripts/rebuilddb.sh rootuser rootpassword database db/laconica.sql
-
- Here, rootuser and rootpassword are the username and password for a
- user who can drop and create databases as well as tables; typically
- that's _not_ the user Laconica runs as.
-11. Use mysql client to log into your database and make sure that the
- notice, user, profile, subscription etc. tables are non-empty.
+10. Rebuild the database. For MySQL, go to your Laconica directory and
+ run the rebuilddb.sh script like this:
+
+ ./scripts/rebuilddb.sh rootuser rootpassword database db/laconica.sql
+
+ Here, rootuser and rootpassword are the username and password for a
+ user who can drop and create databases as well as tables; typically
+ that's _not_ the user Laconica runs as.
+ For PostgreSQL databases there is an equivalent, rebuilddb_psql.sh,
+ which operates slightly differently. Read the documentation in that
+ script before running it.
+11. Use mysql or psql client to log into your database and make sure that
+ the notice, user, profile, subscription etc. tables are non-empty.
12. Turn back on the Web server, and check that things still work.
13. Turn back on XMPP bots and email maildaemon. Note that the XMPP
bots have changed since version 0.5; see above for details.
of the defaults are defined), you will lose your configuration options
in any upgrade, and you will wish that you had been more careful.
+Starting with version 0.7.1, you can put config files in the
+/etc/laconica/ directory on your server, if it exists. Config files
+will be included in this order:
+
+* /etc/laconica/laconica.php - server-wide config
+* /etc/laconica/<servername>.php - for a virtual host
+* /etc/laconica/<servername>_<pathname>.php - for a path
+* INSTALLDIR/config.php - for a particular implementation
+
Almost all configuration options are made through a two-dimensional
associative array, cleverly named $config. A typical configuration
line will be:
authentication will require it. Note that this does not turn
off registration; use 'closed' or 'inviteonly' for the
behaviour you want.
+notice: A plain string that will appear on every page. A good place
+ to put introductory information about your service, or info about
+ upgrades and outages, or other community info. Any HTML will
+ be escaped.
+dupelimit: Time in which it's not OK for the same person to post the
+ same notice; default = 60 seconds.
+logo: URL of an image file to use as the logo for the site. Overrides
+ the logo in the theme, if any.
db
--
This section is a reference to the configuration options for
-DB_DataObject (see http://ur1.ca/7xp). The ones that you may want to
+DB_DataObject (see <http://ur1.ca/7xp>). The ones that you may want to
set are listed below for clarity.
database: a DSN (Data Source Name) for your Laconica database. This is
the client to speed up page loading, either with another
virtual server or with an NFS or SAMBA share. Clients
typically only make 2 connections to a single server at a
- time (http://ur1.ca/6ih), so this can parallelize the job.
+ time <http://ur1.ca/6ih>, so this can parallelize the job.
Defaults to null.
public
---------
You can get a significant boost in performance by caching some
-database data in memcached (http://www.danga.com/memcached/).
+database data in memcached <http://www.danga.com/memcached/>.
enabled: Set to true to enable. Default false.
server: a string with the hostname of the memcached server. Can also
You can get a significant boost in performance using Sphinx Search
instead of your database server to search for users and notices.
-(http://sphinxsearch.com/).
+<http://sphinxsearch.com/>.
enabled: Set to true to enable. Default false.
server: a string with the hostname of the sphinx server.
source: The name to use for the source of posts to Twitter. Defaults
to 'laconica', but if you request your own source name from
- Twitter (http://twitter.com/help/request_source), you can use
+ Twitter <http://twitter.com/help/request_source>, you can use
that here instead. Status updates on Twitter will then have
links to your site.
separate logfile. This is probably the first place to look if you're
getting weird behaviour from Laconica.
-If you're tracking the unstable version of Laconica in the darcs
+If you're tracking the unstable version of Laconica in the git
repository (see below), and you get a compilation error ("unexpected
T_STRING") in the browser, check to see that you don't have any
conflicts in your code.
-If you upgraded to Laconica 0.6.4 without reading the "Notice inboxes"
+If you upgraded to Laconica 0.7.1 without reading the "Notice inboxes"
section above, and all your users' 'Personal' tabs are empty, read the
"Notice inboxes" section above.
================
If you're adventurous or impatient, you may want to install the
-development version of Laconica. To get it, use the darcs version
-control tool (http://darcs.net/) like so:
+development version of Laconica. To get it, use the git version
+control tool <http://git-scm.com/> like so:
- darcs get http://laconi.ca/darcs/ mublog
+ git clone http://laconi.ca/software/laconica.git
-To keep it up-to-date, use 'darcs pull'. Watch for conflicts!
+To keep it up-to-date, use 'git pull'. Watch for conflicts!
Further information
===================
* There is a mailing list for Laconica developers and admins at
http://mail.laconi.ca/mailman/listinfo/laconica-dev
-* The #laconica IRC channel on freenode.net (http://www.freenode.net/).
+* The #laconica IRC channel on freenode.net <http://www.freenode.net/>.
* The Laconica wiki, http://laconi.ca/trac/
Feedback
* Erik Stambaugh
* 'drry'
* Gina Haeussge
-* Ken Sheppardson (Trac server, man-about-town)
-* Tiago 'gouki' Faria (entrans)
* Tryggvi Björgvinsson
+* Adrian Lang
+* Ori Avtalion
+* Meitar Moscovitz
+* Ken Sheppardson (Trac server, man-about-town)
+* Tiago 'gouki' Faria (i18n managerx)
+* Sean Murphy
+* Leslie Michael Orchard
+* Eric Helgeson
+* Ken Sedgwick
Thanks also to the developers of our upstream library code and to the
thousands of people who have tried out Identi.ca, installed Laconi.ca,
projects / quix0rs-gnu-social.git / blobdiff