Designing identifiers for the DDC

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?

Comments

[simonfj]

michael,

just making some notes about this on my lonely part of the net. http://forums.oclc.org/idealbb/view.asp?topicID=11733

You may know Icann has started a .test domain as the beginnings of internationalizing domain names. notes at the forum. If you can answer the question about keyboards it would be appreciated.

One thing I'm trying to work out now is if your mid western team is thinking architecturally in terms of trees (client/server) or webs (P2P). My intuition tells me that the DDC has a role to play in giving hash tables a global architecture, particularly the distributed ones. http://en.wikipedia.org/wiki/Distributed_hash_table