Archive for 2011

Merging two DSpace Solr based data sets together

Tuesday, October 11th, 2011

Have you ever messed up a DSpace upgrade and somehow ended up resetting your DSpace statistics? I did that. When we upgrade DSpace at A&M we preform a fresh install each time and then restore the data from the old instance into the new instance. This involves connecting the database, linking the asset store, and copying the DSpace log directory. We like to do it this way so that our configs are fresh each time. Our documented installation procedures lists the exact settings (about 5) that need to be touched for each production install. All other parameters in the dspace.cfg are maintained in our local SVN copy. This prevents the problem of never know exactly how your DSpace is configured if you do the recommended upgrade procedure by modifying the dspace.cfg each upgrade with new parameters.


Find All Restricted Items Within DSpace

Friday, August 19th, 2011

Here is an SQL query you can copy-and-paste into DSpace to find all items which have restricted access or contain bundles / bitstreams which are restricted. Restricted means that the object does not have an authorization policy enabling anonymous read.

It’s actually quite hard to find the absence of something with SQL. After trying various methods the way I came up with to solve this problem is a sub select that counts how many anonymous access policies exist for each object and if there are none then report those. The query is broken down into three distant parts one for each object time. Then all the objects are combined via PostgreSQL set operators and sub selects (again!). This means that if you have a huge number of restricted items in your repository the query might fail or take an obscene amount of time/memory to run. I tried using a left outer join but couldn’t get it to handle the case where both no access policies exists and only non anonymous access policies exist.

The approach used here is inelegant and has some serious performance problems. However it worked my immediate purpose. We had no idea how many or which items are restricted in our repository (answer: just under 300). This task is a good candidate for a DSpace curation task, to find all items in a collection which are have restricted access. Or the opposite, find all items which are NOT restricted.


Preserving Character Encodings of a DSpace Metadata Export using MS Excel 2011 on OS X

Wednesday, July 20th, 2011

Stencil Alphabet The problem I recently ran into was updating the metadata for a particular collection that was being moved from TDL’s repository into A&M’s repository. I able to quickly move the collection into the new repository using OAI-PMH harvesting with ORE support. However, the metadata needed a bit of cleaning up for it’s new repository home, such as changing to and inconsistent formats used in other fields. This is a perfect task for Stuart’s Bulk Metadata Export tool. This DSpace feature allows an administrator to download a Comma Separate Values (CSV) file of all the metadata in a particular collection, then open it up in MS Excel and edit the metadata naturally. Finally once the metadata is ready to go you can upload it back to the repository and all the fields will be updated correctly. It is a very nice feature that can save a ton of time.

The Problem

When I opened the file in Excel some of the characters were not showing up correctly. Specifically characters in titles and names which used non-English marks, in this case there were all from the extended Latin character set. If you ignore these problems, later when you try to upload the CSV file DSpace will pick up on these changes and cause the garbled characters to be introduced into the repository.


SvnBot 1.1 Released

Friday, February 25th, 2011

The SvnBot is a simple single purpose IRC robot that monitors one or more SVN repositories. When changes are committed to a source repository the robot makes an announcement in an IRC channel. The purpose of the tool is to allow a team of developers to keep up to date on changes that other team members are making. Here at TDL we have a geographically distributed team of software developers some in Austin and Lubbock along with my self in College Station. This is one tool that helps the team keep in sync with each other.

There are already many tools available that do this task [1][2][3], however they all require the use of SVN commit-hooks. Commit-hooks are run on the repository’s server allowing external tools to be notified when specific events occur. Using commit-hooks can work reasonably well if you have access to the server’s configuration, but that is not always the case. Instead of relying on commit-hooks; the SvnBot runs independently, periodically polling the repository for any updates. When an update in found a message will be announced in IRC.

Below is an example IRC message. The message includes the author and their commit message along with some brief statistics about the number of files affected and a URL. If multiple files were affected by a single commit then the url reported is to the common path, i.e. the closest directory that contains all the affected files.

Scott: “SAND-30, reviewed the pom file: removing unneeded dependencies, declaring output to be UTF-8 and added a few comments.(Rev 666: 1 file modified)

Special thanks to the Texas Digital Library, my employer, for allowing me to release this as an open source project.

Mixed XML and Property files?

Tuesday, February 1st, 2011

Have you ever wanted the simplicity of a plain old Java properties file but with just a little bit of grouping provided by XML? I’ve been working on a small side-project recently and it requires a simple configuration file of a dozen items or so. The project needed a repeatable set of configuration parameters, so that it could connect to several SVN servers. Each connection needed a URL, username, password, and a few other ancillary properties. This is a pain to do in a plain old properties file. You have to do something with the naming of the properties to relate them together, such as:

property.1.url = http://...
property.1.username = Bob
property.1.password = Bob’s secret

property.2.url = http://...
property.2.username = Joe
property.2.password = Joe’s secret  

This way works but it’s sort of annoying and can be confusing for someone else to understand what’s going on. They would likely need to read the documentation, especially if it’s more complex with multiple types of repeating parameters. There are several alternatives, you could try encoding all the parameters into one property but that’s even harder for a user to figure out. A slightly better alternative is to use something hierarchical like XML, thus:

		<password>Bob’s secret</password>
		<password>Joe’s secret</password>

This is easier to understand, but it’s very verbose. Each property is labeled twice, once to open the tag and again to close the tag. XML is good for complex things like HTML or specific file formats with a dedicated reader. However, XML is not great for humans to read, let alone edit quickly.

A better solution, combine both!

Instead of either XML or properties file we can munge the two together to create something that is easier for users to manage. = value1
property.two = value2

	url = http://...
	username = Bob
	password = Bob’s secret

	url = http://...
	username = Joe
	password = Joe’s secret

The combined format is similar to Apache’s httpd configuration format where name/value pairs are also mixed with nestable elements. It’s very close to the simplicity of a plain old properties file, but has just enough expressivity to handle grouping of elements. It’s a win-win.