Protocol Design by Committee

3M's Standard Interchange Protocol (SIP, not to be confused with the "Session Initiation Protocol" used in internet telephony) is the protocol that library self-check units use to talk to the circulation module of a library's Integrated Library System. It's a small, focused protocol that was designed by people who: knew what they were trying to accomplish, had to implement it, and had to make it work on the low-end computers that get stuffed into the self-checkout units, and over the (potentially slow and crappy) communication lines that a small library system might have.

NCIP is the NISO Circulation Interchange Protocol. This protocol was designed as a "vendor-neutral" replacement for the 3M SIP. The standards committee allowed themselves to be seduced by both new technologies and mission creep that encouraged them to attempt to design a system that could handle all circulation activities, including not just patron self-check, but also inter-library borrowing and the accounting that goes with it. What they produced was... larger than one might expect, given the size of the documents.

For example, when a self-checkout unit wants to verify that a user is valid with SIP, it sends this message:

2300020060221 211723AOLochalsh Public\ Library|AAdjfiander|AC|AD|AY1AZEA14

When a self-checkout unit is using NCIP, it sends this XML:

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE NCIPMessage PUBLIC "-//NISO//NCIP DTD Version 1//EN"
     "http://www.niso.org/ncip/v1_0/imp1/dtd/ncip_v1_0.dtd">
<NCIPMessage version="http://www.niso.org/ncip/v1_0/imp1/dtd/ncip_v1_0.dtd">
    <AuthenticateUser>
        <IntiationHeader>
        <FromAgencyId>
            <UniqueAgencyId>
            <Scheme>local-name</Scheme><Value>Taylor-SC-1</Value>
        </UniqueAgencyId>
        </FromAgencyId>
        <FromAgencyAuthentication>xyzzy</FromAgencyAuthentication>
         <ToAgencyId>
            <UniqueAgencyId>
            <Scheme>local-name</Scheme><Value>UWOLS</Value>
        </UniqueAgencyId>
        </ToAgencyId>
       </IntiationHeader>
       <AuthenticationInput>
           <AuthenticationInputData>djfiander</AuthenticationInputData>
       <AuthenticationDataFormatType>
           <Scheme>http://www.iana.org/assignments/media-types</Scheme>
           <Value>text/plain</Value>
       </AuthenticationDataFormatType>
       <AuthenticationInputType>
           <Scheme>http://www.niso.org/ncip/v1_0/imp1/schemes/authenticationinputtype/authenticationinputtype.scm</Scheme>
           <Value>User ID</Value>
       </AuthenticationInputType>
       </AuthenticationInput>
    </AuthenticateUser>
</NCIPMessage>

Need I say more?