Connecting Applications Together the Web Way by ProQuest

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									»   libraries
    in computers
                                                                              by daniel chudnov
                                                                                             Information Technology Specialist
                                                                                                  Office of Strategic Initiatives
                                                                                                           Library of Congress




                                               Connecting Applications
                                                Together the Web Way

         I’VE BEEN       I’ve been obsessing over how to connect       Both my front end and the remote back end
                     web applications to each other for as long as     were on the web, and the PHP language had
                     I’ve been a working librarian. This obsession     recently gained a function called “include()”
       OBSESSING     dates from my start at my first job. When I       that could fetch the data from a URL and
                     look back through the intervening years and       read it right in for you inside your code.
    OVER HOW TO      squint just right, a few lessons emerge about        When I saw that it worked, I ripped out all
                     how technology changes and when my obses-         that expensive plumbing and connected the
                     sion-driven expectations about these changes      front end to the back end by having the front
    CONNECT WEB      are either met or are way off the mark.           end get data from the back end with a simple
                         I was pretty certain, early in my career,     HTTP call (i.e., a plain old web request). That
     APPLICATIONS    that there was a future in this concept we call   was easy! I’d spent months imagining a com-
                     “mashups,” only nobody was calling it that        plicated solution was required before I real-
                     yet, and we didn’t even have the name “web        ized that lots of other people had long before
         TO EACH     services” yet either. The arrival of services     me had the same need, so they just baked a
                     such as PubMed, though—with their rich            simple solution right there into the language
    OTHER FOR AS     data sources, standard URL patterns for           I was using. My app got simpler, smaller, and
                     queries, and specifying details about result      more cost-effective, and I was able to focus on
                     sets—coincided with my start as a hacker/li-      making it better instead of having to con-
     LONG AS I’VE    brarian in a real job at a medical library. So,   stantly fiddle with making the back end con-
                     of course, I hacked up a few mashup views of      nection work. With all that new free time, I
           BEEN A    data from PubMed. At first, I worked on a         figured out a way to make the system link au-
                     novel graphical local user interface (UI). Back   tomatically to online journal articles from the
                     in 1997, I thought I needed to use Common         abstracts. After that, I figured out how to
        WORKING      Object Request Broker Architecture (if you        bring a system online that let other people
                     don’t know, don’t ask!) to wire up the graph-     connect abstracts to articles too. The simple
       LIBRARIAN.    ical UI front end to the PubMed data source       solution to supporting this was to make the
                     back end, because they were different sys-        data in my system easily queried with a sim-
                     tems (one local, one remote) and I wrote a lot    ple URL pattern, just like PubMed had done
                     of plumbing to connect them together. This        in allowing me to mash up its data. This so-
                     took lots of work, lots of money, and a lot of    lution was a precursor to the OpenURL
                     software design, but a funny thing happened       model, and several people were able to mash
                     once I got it working. I didn’t need any spe-     up my mashup to work inside their own li-
                     cial plumbing, let alone expensive plumbing.      brary sites. This worked for several years

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