Public utility tariffs are typically established through a formal administrative process that legally certifies rates (prices) and makes them public. Hence, these prices differ significantly from commercial prices established without any specific public administrative process. The difference between public utility tariffs and commercially established prices is under-appreciated. The web and technologies for semantic mark-up can make public utility tariffs a valuable, open-data product of the public administrative process.
Tariff regulation has tended to focus on rate-making principals. In the U.S., the Interstate Commerce Act of 1887 addressed railroad “common carrier” rates. The Act required that railroad rates be “reasonable and just” and prohibited giving “undue or unreasonable preference or advantage” to any railroad customer or type of railroad traffic. Similar rules have been extended to a variety of services, including some in the water, energy, trucking, and communications sectors. What exactly these rules mean is typically a matter of contentious administrative and political debates. Those most willing to invest time, money, and effort into these debates have been businesses with significant financial interests in tariff decisions and politicians and interest groups who see opportunities for scoring news-marketable symbolic victories.
The Interstate Commerce Act, however, was also quite concerned with making tariffs public. Section 6 of the Act required a plain statement of rates and conditions to be made available for public inspection. Ten days’ public notice was required for an increase in rates. Reductions in rates could be made immediately, but they also were required to be publicly posted immediately. The Act’s requirements for making rates public were quite specific in terms of the communications technology of the time:
Such schedules shall be plainly printed in large type, of at least the size of ordinary pica, and copies for the use of the public shall be kept in every depot or station upon any such railroad, in such places and in such form that they can be conveniently inspected.
The Act also gave the newly formed Interstate Commerce Commission broad powers to adopt new communication technologies:
said Commission shall from time to time prescribe the measure of publicity which shall be given to such rates, fares, and charges, or to such part of them as it may deem it practicable for such common carriers to publish, and the places in which they shall be published
In response to the Act, some common carriers used what were called “midnight tariffs”. The basic idea was to tip-off a favored customer about an obscure reduction in a tariff just before the old tariff was re-enacted. Thus no other customer but the informationally favored customer got the lowered tariff rate. In response to such abuse, Congress amended the Interstate Commerce Act to require 30 days’ notice for a tariff increase or decrease. 
Tariffs are now typically available on the web in forms that humans and data-gathering software applications cannot readily read. British Telecom, for instance, has online Price Lists that presents a huge amount of relatively unstructured information. Only a well-informed human could easily make sense of this information. In the U.S., tariffs filed at the Federal Communications Commission (FCC) are available through the FCC’s Electronic Tariff Filing System. Tariffs in that system are pdf documents describing rates and terms. Only a well-informed human could easily make sense of this information. Tariffs are not generally available in ways that make tariff information most useful to the widest range of persons and applications, given up-to-date communications technologies.
Presenting tariff data with standard mark-up technologies and vocabularies would be a valuable contribution to open-data ecologies. Smart-grid systems for more efficient energy consumption need structured, software-interpretable price data. Efficient use of communications networks requires not just standardized, real-time propagation of technical routing tables but also standardized, real-time propagation of prices associated with different routes and services. More generally, requiring that tariffs be public knowledge openly available to applications would discipline and leverage administrative and legal resources used in the public process of establishing tariffs. Tariffs under such a process would look nothing like current tariffs.
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 In British English, tariff is more or less synonymous with price. The relevant distinction is between prices certified through a public administrative process and prices not certified through such a process.
 Amendment enacted on June 29, 1906.