Why can't a library be more like a bookshop?

One of the things I have found most difficult to get my head around – and certainly difficult to explain to other people – is the difference between classification and shelfmark. 

Classification is a representation of the subject (or subjects) of an item.

The shelfmark is the item’s address within the library – and tells you where to find it. 

Very often, because we usually shelve in classified order, the shelfmark is a classification number or has a classification number as one of its elements (along with a filing suffix, for example), which is where the confusion starts to creep in.  It isn’t helped by a tendency to refer to “main” and “added” classification, with the classification which is included in the shelfmark being the “main” number and anything else being “added” (and often therefore regarded as an unnecessary extra). Gradually people start to think that the shelfmark IS the classification; so that when colleagues working in reader services return a book to bib services and ask for it to be “reclassified”, what they usually mean is that they want the shelfmark changed.

What I am beginning to wonder is, whether it should be any part of a cataloguer’s job to allocate the shelfmark – whether this couldn’t be done locally by staff in each library. I take it as an article of faith that classification certainly is the cataloguer’s job – the analysis of the subject of an item and its correct representation in the classification scheme, together with the creation of subject headings and/or subject index entries, should be done rigorously and consistently by staff trained in the theory and practice of classification. But is it up to us to decide where in the library that item is kept?

Why do we think it matters that all copies of a book should have the same shelfmark? Why, if a book is returned to us with the request that it be “reclassified” (i.e. that its shelfmark be changed) so that the users may find it more easily, do we change the shelfmarks of all copies of that book? All copies should be classified the same way, because it is the book that we are classifying, not each individual copy; but each copy can have its own shelfmark without affecting anything at all.

Bookshops do this all the time, of course.  The biography of a footballer may have copies put in both the sport and the biography sections;  a detective novel set in ancient Rome may be found in both the Historical and the Crime sections. In libraries we have always been a bit sniffy about this and prided ourselves upon always being consistent– all our copies will be either in one place or another, not scattered between them.  It's as if we think that consistency of shelfmarks makes a library in some way intellectually superior to a bookshop. But wouldn’t it be better if libraries were more like bookshops and put the books where we thought the users would find them, even if that meant they were shelved in different places in different libraries (or even in different places within the same library)? The casual user browsing along the shelves would be more likely to find what they were looking for and anyone using the catalogue would still be able to find all the copies each with their own shelfmark. 

I suspect what happens now, is that library staff often put their books in places other than at the shelfmark given on the catalogue, because they know better than the staff in bib services where that book will be looked for; but, because we have made library staff think that shelfmarks shouldn’t be altered, can’t be altered, this is done surreptitiously, without the shelfmark on the catalogue being changed – which means that no one using the catalogue will be able to find the book, because they’ll be looking in the wrong place. Isn’t it time that we separated shelfmarks and classmarks and used them each for their proper purpose?