Although the Dewey
Decimal Classification is currently available on the web to subscribers as
WebDewey and Abridged WebDewey in the OCLC Connexion service and in an XML version to licensees,
OCLC does not provide any “web services” based on the DDC. By web services, we
mean presentation of the DDC to other machines (not humans) for uses such as
searching, browsing, classifying, mapping, harvesting, and alerting.
In order to build
web-accessible services based on the DDC, several elements have to be
considered. One of these elements is the design of an appropriate Uniform
Resource Identifier (URI) structure for Dewey.
The design goals of
mapping the entity model of the DDC into an identifier space can be summarized
as follows:
- Common locator for Dewey concepts and associated resources for use in web services and web applications
- Use-case-driven, but not directly related to and outlasting a specific
use case (persistency)
- Retraceable path to a concept rather than an abstract identification,
reusing a means of identification that is already present in the DDC and
available in existing metadata
We have been working
closely with our colleagues in the OCLC Office of Research (especially Andy
Houghton as well as Eric Childress, Diane Vizine-Goetz, and Stu Weibel) on a
preliminary identifier syntax. The basic identifier format we are currently
exploring is:
http://dewey.info/{aspect}/{object}/{locale}/{type}/{version}/{resource}
where
- {aspect} is the aspect
associated with an {object}—the current value set of aspect contains “concept”,
“scheme”, and “index”; additional ones are under exploration
- {object} is a type of {aspect}
- {locale} identifies a
Dewey translation
- {type} identifies a Dewey
edition type and contains, at a minimum, the values “edn” for the full edition or
“abr” for the abridged edition
- {version} identifies a
Dewey edition version
- {resource} identifies a
resource associated with an {object} in the context of {locale}, {type}, and
{version}
Some examples of
identifiers for concepts follow:
<http://dewey.info/concept/338.4/en/edn/22/>
This identifier is used
to retrieve or identify the 338.4 concept in the English-language version of Edition
22.
<http://dewey.info/concept/338.4/de/edn/22/>
This identifier is used
to retrieve or identify the 338.4 concept in the German-language version of Edition
22.
<http://dewey.info/concept/333.7-333.9/>
This identifier is used
to retrieve or identify the 333.7–333.9 concept across all editions and
language versions.
<http://dewey.info/concept/333.7-333.9/about.skos>
This identifier is used
to retrieve a SKOS representation of the 333.7-333.9 concept (using the “resource” element).
There are several open
issues at this preliminary stage of development:
Use cases: URIs
need to represent the range of statements or questions that could be submitted
to a Dewey web service. Therefore, it seems that some general questions have to
be answered first: What information does an agent have when coming to a Dewey
web service? What kind of questions will such an agent ask?
Placement of the {locale} component: It is still an open question if the {locale}
component should be placed after the {version} component instead
(<http://dewey.info/concept/338.4/edn/22/en>) to emphasize that the most
important instantiation of a Dewey class is its edition, not its language
version. From a services point of view, however, it could make more sense to
keep the current arrangement, because users are more likely to come to the
service with a present understanding of the language version they are seeking
without knowing the specifics of a certain edition in which they are trying to
find topics.
Identification of other Dewey entities: The goal is to create a locator that does not answer
all, but a lot of questions that could be asked about the DDC. Which entities
are missing but should be surfaced for services or user agents? How will those
services or agents interact with them? Should some entities be rendered in a
different way as presented? For example, (how) should the DDC Summaries be retrievable? Would it be necessary to make the DDC Manual accessible through this identifier structure?
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