Tag Archives: collection development


Overall, in the world of libraries, Patron Driven Acquisition (PDA) and Demand Driven Acquisition (DDA) appear to be used synonymously (see http://www.academia.edu/5868319/Does_PDA_DDA_really_mean_Patron-driven_Acquisition). As noted in this presentation, “Demand Driven Acquisition” (DDA) [is] [G]enerally understood to be a synonym of PDA.” However, as last week’s presenters aptly pointed out, the authors of “Streaming Video in Academic Libraries” noted the following: “Libraries can also choose from a couple of other models: patron-driven acquisition (PDA) and demand-driven acquisition (DDA). In both models, libraries choose the packages to add to their collections. In the PDA model, a lease or purchase of a film is triggered after a certain number of user views, usually four or five. PDA funds are paid up front with a flexible deposit amount—very helpful for smaller library budgets. Meanwhile, the DDA model allows librarians to choose leases or purchases after examining user viewing data; it generally requires a library to agree to a higher minimum deposit in order to participate.”

So what’s up? As far as I can tell, DDA *is* generally understood to be a synonym of PDA, and vice versa. However, some vendors have made distinctions between the two. EBSCO has both DDA and a PDA services, both of which they notes as being “similar” to one another: “GOBI customers can access EBSCO titles through Demand-Driven Acquisitions (DDA), allowing libraries to pre-select titles that are only purchased when patron usage determines need” (http://www.ybp.com/newsarchive/1110_ebl.html). Therefore, with DDA it sounds like libraries have have the ability to “pre-select” content that patrons can then choose from. EBSCO’s PDA is more automated, allowing the patron to select from a wider breadth of material for automatic purchase: https://help.ebsco.com/interfaces/EBSCOhost_Collection_Manager/ECM_User_Guide/What_is_PDA_in_ECM. This distinction is murky, and EBSCO’s websites don’t help with clarifying the two, though it seems that DDA gives the librarian more of an opportunity to narrow down the content for the patron’s automated purchases.

I believe the definition of DDA used by the Streaming Video authors are more inline with what is commonly understand as “Usage Driven Acquisitions” (UDA) or “Evidence Based Acquisitions” (EBA): “It differs in requiring an upfront monetary commitment or deposit. This gives the library access to a defined collection of content. At the end of the agreed upon time period, usage stats of the accessible content is provided to the library. The library then decides which titles to own. The list prices of titles chosen generally total to the amount of initial commitment/deposit. ‘Evidence Based Acquisitions,’ another new label within PDA/DDA models. Seems most similar to Usage-Driven Acquisition” (http://www.slideshare.net/klm-shsu/pda-dda-uda-omg).

Confused? Good! I think it’s meant to be that way (I believe vendors think of these terms less as standardized mechanisms for delivering content, and more as marketing inroads that may—or may not—actually be patron, user, demand or evidence driven). Just take this away:

  • PDA/DDA puts selection power in the hands of the patron, while EDA/UDA gives librarians data about use from they can make selection decisions.

Now for the big question: will the PDA/DDA model replace librarians? https://www.insidehighered.com/news/2012/06/20/research-foresees-demand-driven-book-acquisition-replacing-librarians-discretion