Category Archives: Databases

The Trouble with OR

A Dictionary of Philosophy (Pan Reference 1979) lists two definitions for OR. One is exclusive, as in ‘all trees are either deciduous or evergreen’ (one cannot be both), while other is inclusive: ‘he is either dense or stupid, and possibly both’.

The trouble with OR in database searching is that it uses the inclusive definition only and a lot of people use OR in the exclusive sense (you can have vanilla OR pistachio icecream [but not both]). How many times have you come across confusion when trying to explain to novice database searchers the concept of OR? I have. How can librarian teachers explain how this function works satisfactorily?

I think we have to acknowledge that OR can be used in two ways and that databases use only one. We have to explain this to people when we are first introducing them to searching databases, while being careful about using the word in explanation not directly referring to the operator. Perhaps the easiest way to explain this is the Venn diagram, commonly used in library training.

OR, along with AND, NOT and nesting, are logic operators and are used in logic (philosophy) and mathematics. I’ve had success in describing nesting as a mathematical concept where the first action that occurs is the query in the inner bracket, then it expands – bit like a Russian doll set in reverse!

At the moment, I am having an argument with other librarians about OVID’s use of descriptive terms in the subheadings section to describe AND and OR. This is what OVID says:

  • Choose Combine with AND to search for the intersection of two or more subheadings.
  • Choose Combine with OR to search for the union of two or more subheadings.

This is wrong to me – and my philosopher husband agrees. You have to look at a truth table to see how OR and AND work. Boolean truth table

The definition of union is ‘to join’. Just think of the marriage ceremony – this man to the exclusion of all others (it doesn’t mean plus his brother or uncle when desired!). Intersection is ‘to cross’ and this definition only works when you consider the middle of the intersection where all the roads meet. BUT then the roads diverge and the traveller can only take one direction – straight head or turn left? This is the exclusive use of OR – you can go in one direction only – you can’t do both but you do have a choice. Databases use the inclusive definition so leaving the intersection infers that you can go straight ahead only, straight ahead as well as turning left PLUS  left only – magic!! You can’t be in two places at once.





Searching the literature to inform HTA

The EText on Health Technology Assessment (HTA) Information Resources was permanently archived on the NIH website in 2006. This ebook, although originally put together about 18 years ago, is still a valuable guide for the novice HTA librarian or researcher. The information and processes described in this book is still valid but of course many of the tools are now unavailable. There are still some that are around such as ERIC (education database), HSRProj (health services research projects), (US and extramural funded trials) and others but for updated tools and resources about search methods, check out SUREInfo on the HTAi Vortal.

Catherine goes to prison

prisonLast Friday, I went to visit a Forensicare researcher at the Melbourne Assessment Prison (formerly the Melbourne Remand Centre). Our library services a large range of groups who work in a variety of locations. Forensicare staff work in high security sites as well as in the community. This researcher worked in a prison and I thought it would be an interesting excursion to visit her (OK, I was very curious – I’ve never visited a prison before) and sometimes, showing a person how to search databases etc works better if they are in a familiar environment. It was raining when I left work to get on the tram and by the time I was at LaTrobe St, it was pouring heavily. My trousers were almost soaking! The researcher met me at reception and I signed in. Then I passed over my passport and staff ID for ID purposes to the guard and was then given a blue bracelet and visitor lanyard.. I had to put all my stuff in a locker – not even allowed to bring a pen in, but allowed paper. I had my sheaf of library bumpf and how-tos – that was allowed. Then we passed through a body scanner and then another scanner (this was for items being brought in ). Then to get to the staff meeting room with a PC, we had to go through 3 or 4 heavy doors with eye scanners. The researcher had to lift the flap and look into the scanner. At one guard point, it was looking in the eye scanner for her and for me, holding up my wrist to the window to show the guard I had been processed by the guards at entry. Past the first heavy door was the prisoner visitor communication booths. It was quite small and cramped looking. The building looks quite large from the outside but inside, from the areas I saw anyway, it was quite small. I guess the walls are very thick. I was warned it would take a long time getting through (it took about 30mins) and before I even got to this point, I had to provide the researcher with some personal details in order to be approved.

How can I end this post? If you have clients in multiple locations, it is worthwhile to do site visits. Not every client is able to physically visit the library for instruction sessions or research advice. Not only is it an excursion for you, it is also an opportunity to see what their work environment is like – what is technologically possible and what work-arounds could work. Next up is a visit to the Royal Park campus.