Interesting, thanks for the additional information, very useful!

I don't like relying on the 'free text' in subfield 3, because it seems 
fragile, who knows if I know all the possible values or if they change 
them in the future breaking my code.

But your example with two 'full text' links is enlightening.

I think what I'm liking as an algorithm for my needs (any full text is 
better than none, but PDF is best) -- is first looking for an 856 with 
second indicator "0" -- if there's only one, use it. If there are more 
than one, try to find one that includes the substring "PDF", if none do, 
just use the first one.

Jonathan

On 2/17/14 11:16 AM, Andrew Anderson wrote:
> The document you want to request from ProQuest support was called Federated-Search.docx when they sent it to me.  This will address many of your documentation needs.
>
> ProQuest used to have an excel spreadsheet with all of the product codes for the databases available for download from http://support.proquest.com/kb/article?ArticleId=3698&source=article&c=12&cid=26, but it appears to no longer be available from that source.  ProQuest support should be able to answer where it went when you request the federated search document.
>
> You may receive multiple 856 fields for Citation/Abstract, Full Text, and Scanned PDF:
>
> =856  41$3Citation/Abstract$uhttp://search.proquest.com/docview/...
> =856  40$3Full Text$uhttp://search.proquest.com/docview/...
> =856  40$3Scanned PDF$uhttp://search.proquest.com/docview/...
>
> I would suggest that rather than relying on the 2nd indicator, you should parse subfield 3 instead to find the format that you prefer.  You see the multiple 856 fields in the MARC records for ProQuest holdings as well, as that is how ProQuest handles coverage gaps in titles, so if you have ever processed ProQuest MARC records before, you should be already prepared for this.
>