Tag: web

Working with Web Curator Tool (part 1)

Keen readers may recall a post from April 2008 about my website-archiving forays working with Web Curator Tool, the workflow database, used for programming Heritrix, the crawler which does the harvesting of websites.

Other UKWAC partners and myself have since found that Heritrix sometimes has a problem, described by some as ‘collateral harvesting’. This means it can gather links, pages, resources, images, files and so forth from websites we don’t actually want to include in the finished archived item.

Often this problem is negligible, resulting in a few extra KB of pages from adobe.com or google.com for example. Sometimes though it can result in large amounts of extraneous material, amounting to several MB or even GB of digital content (for example if the crawler somehow finds a website full of .avi files.)

I have probably become overly preoccupied with this issue, since I don’t want to increase our sponsor (JISC)’s overheads by occupying their share of the server space with unnecessarily bloated gathers, nor clutter up the shared bandwidth by spending hours gathering pages unnecessarily.

Web Curator Tool allows us two options for dealing with collateral harvesting. One of them is to use the Prune Tool on the harvested site after the gather has run. The Prune Tool allows you to browse the gather’s tree structure, and to delete a single file or an entire folder full of files which you don’t want.

The other option is to apply exclusion filters to the title before the gather runs. This can be a much more effective method. The method is to enter a little bit of code in the ‘Exclude Filters’ box of a title’s profile. The basic principle is using the code .* for exclusions. .*www.aes.org.* will exclude that entire website from the gather. .*/images/.* will exclude any path containing a folder named ‘images’.

So far I generally find myself making two types of exclusion:

(a) Exclusions of websites we don’t want. As noted with collateral harvesting, Heritrix is following external links from the target a little too enthusiastically. It’s easy to identify these sites with the Tree View feature in WCT. This view also lets you know the size of the folder that has resulted from the external gathering. This has helped me make decisions; I tend to target those folders where the size is 1MB or larger.

(b) Exclusions of certain pages or folders within the Target which we don’t want. This is where it gets slightly trickier, and we start to look in the log files of client-server requests for instances where the browser is staying in the target, but performing actions like requesting the same page over and over. This can happen with database-driven sites, CMS sites, wikis, and blogs.

I believe I may have had a ‘breakthrough’ of sorts with managing collateral harvesting with at least one brand of wiki, and will report on this for my next post.

Digital preservation in a nutshell, part II

As Richard noted in Part I, digital preservation is a “series of managed activities necessary to ensure continued access to digital materials for as long as necessary.” But what sort of digital materials might be in scope for the PoWR project?

We think it extremely likely that institutional web resources are going to include digital materials […]

Originally published on the JISC-PoWR blog.

As Richard noted in Part I, digital preservation is a “series of managed activities necessary to ensure continued access to digital materials for as long as necessary.” But what sort of digital materials might be in scope for the PoWR project?

We think it extremely likely that institutional web resources are going to include digital materials such as “records created during the day-to-day business of an organisation” and “born-digital materials created for a specific purpose”.

What we want is to “maintain access to these digital materials beyond the limits of media failure or technological change”. This leads us to consider the longevity of certain file formats, the changes undergone by proprietary software, technological obsolescence, and the migration or emulation strategies we’ll use to overcome these problems.

By migration we mean “a means of overcoming technological obsolescence by transferring digital resources from one hardware/software generation to the next.” In contrast, emulation is “a means of overcoming technological obsolescence of hardware and software by developing techniques for imitating obsolete systems on future generations of computers.”

Note also that when we talk about preserving anything, “for as long as necessary” doesn’t always mean “forever”. For the purposes of the PoWR project, it may be worth us considering medium-term preservation for example, which allows “continued access to digital materials beyond changes in technology for a defined period of time, but not indefinitely.”

We also hope to consider the idea of life-cycle management. According to DPC, “The major implications for life-cycle management of digital resources is the need actively to manage the resource at each stage of its life-cycle and to recognise the inter-dependencies between each stage and commence preservation activities as early as practicable.”

From these definitions alone, it should be apparent that success in the preservation of web resources will potentially involve the participation and co-operation of a wide range of experts: information managers, asset managers, webmasters, IT specialists, system administrators, records managers, and archivists.

(All the quotations and definitions above are taken from the DPC’s online handbook.)

Digital preservation in a nutshell (Part I)

One of the goals of PoWR is to make current trends in digital preservation meaningful and relevant to information professionals with the day-to-day responsibility for looking after web resources. Anyone coming for the first time to the field of digital preservation can find it a daunting area, with very distinct terminology and concepts. Some of […]

From the JISC-PoWR Project blog.

One of the goals of PoWR is to make current trends in digital preservation meaningful and relevant to information professionals with the day-to-day responsibility for looking after web resources. Anyone coming for the first time to the field of digital preservation can find it a daunting area, with very distinct terminology and concepts. Some of these are drawn from time-honored approaches to managing things like government records or institutional archives, while others have been developed exclusively in the digital domain. It is an emerging and evolving field that can take some time to get your head round: so we thought it was a good idea to offer a series of brief primers.

Starting, naturally, with digital preservation: this is defined as a “series of managed activities necessary to ensure continued access to digital materials for as long as necessary” (Digital Preservation Coalition, 2002). Continue reading “Digital preservation in a nutshell (Part I)”