This is a guest post from Sam Adams. (We have been using Pubcrawler in the Open Biblio 2 project to create reference collections of journal articles, and hope to continue this work further; this is a brief introduction to the software. Code is currently available in http://bitbucket.org/sea36/pubcrawler)
Pubcrawler collects bibliographic metadata (author, title, reference, DOI) by indexing journals’ websites in a similar manner to the way in which search engines explore the web to build their indexes. Where possible (which depends on the particular publication) it identifies any supplementary resources associated with a paper, and whether the paper is open access (i.e. readable without a subscription or any other charge) – though it cannot determine the license / conditions of such access.
Pubcrawler was originally developed by Nick Day as part of the CrystalEye project to aggregate published crystallographic structures from the supplementary data to articles on journals’ websites. Since then Pubcrawler has been extended to collect bibliographic metadata and support a wider range of journals than just those containing crystallography. Some of the activities Pubcrawler can currently support are:
- Providing core bibliographic metadata
- Identifying collections of open access articles
- Identifying freely accessible supplementary information, which is often a rich source of scientific data
When pointed at a publisher’s homepage Pubcrawler will generate a list of the journals on the site and then crawl the issues’ tables of contents, recording the bibliographic metadata for the articles that it discovers. Pubcrawler uses a combination of two approaches to crawling a journal: starting at the current issue it can follow links to previous issues, walking the journal’s publication history, and if a journal’s website contains a list of issues it will also use that as a source of pages to crawl. When necessary, such as to identify supplementary resources, Pubcrawler can follow links to individual articles’ splash pages.
Pubcrawler does not index any content that is restricted by a journal’s paywall – it has been designed not to follow such links, and as added protection it is run over a commercial broadband connection, rather than from inside a University network to ensure that it does not receive any kind of privileged access.
While Pubcrawler’s general workflow is the same for any publication, custom parsers are required to extract the metadata and correct links from each website. Generally publishers use common templates for their journals web pages, so a parser only needs to be developed once per publishers, however in some instances, such as where older issues have not been updated to match the current template, a parser may need to support a variety of styles.
Pubcrawler currently has parsers (in varying states of completeness) for a number of publishers (biased by its history of indexing published Crystallographic structures):
- The American Chemical Society (ACS)
- The International Union of Crystallography (IUCr)
- The Royal Society of Chemistry (RSC)
And to date it has indexed over 10 million bibliographic records.
There are many other publishers who could be supported by Pubcrawler, they just require parsers to be created for them. Pubcrawler requires two types of maintainance – the general support to keep it running, administer servers etc, that any software requires, and occasional updates to the parsers as journal’s websites change their formatting.