NLM DTD Resources
The NLM Journal
Archiving and Interchange DTD Suite, co-authored by Inera Inc.,
Technologies, and NCBI,
is the de facto standard full-text DTD for scholarly publishing.
Since the DTD was first released in April 2003, it has been (for the
scholarly publishing world) rapidly adopted. Whereas ISO 12083 never achieved
broad acceptance, the NLM DTD has already been adopted by hundreds
of journals (probably north of 500) worldwide. Many small and medium-sized
publishers have adopted the NLM DTD, and a number of larger publishers are
preparing to deliver content according to the NLM DTD when asked. Most of
the major journal publishing compositors and service suppliers are up to
speed on the DTD and happy to deliver content tagged with it.
The NLM DTD has also proven popular with aggregators. It is the "house"
DTD of Atypon
Systems and the recommended DTD for full-text content at
And, of course, NLM uses it for PubMed Central.
The NLM DTD has been no less popular with libraries. In a
joint press release,
the British Library and the
Library of Congress announced that
they would support the NLM DTD as their archiving standard for electronic content.
It has also been adopted by Portico
(a major Mellon-funded archive effort).
NLM DTD FAQ
Q: The DTD is from NLM. Isn't it just for life sciences content?
A: No. The DTD is designed for all scholarly content.
The very first step in design of the DTD by the authors was to review a
large number of journals published outside of life sciences (e.g.,
economics, physics, archeology, history, etc.). Based on this analysis,
the DTD was developed to serve the entire scholarly publishing community.
Q: How easy is it to transform content from another STM
DTD to the NLM DTD?
A: One of the design mandates for the NLM DTD
project was to facilitate easy conversion of content from other DTDs
to the NLM DTD. The DTD designers reviewed more than 35 journal publishing
DTDs as part of their design work to ensure that content tagged in a wide
variety of DTDs and styles could be transformed reliably to the NLM DTD.
Q: I have unusual semantic tagging requirements for my content.
How can these requirements be accommodated in the NLM DTD?
A: The NLM DTD was designed in an open and modular
fashion. In most cases, specific semantic requirements can be handled by
the use of attributes within the DTD. For example, one publisher with
botanic taxonomies completed the tagging quite easily by using the
attributes provided within the definition list and named-content elements.
However, if custom extensions are necessary, the DTD has also been built
so that publishers can extend the DTD with new
elements to meet their specific requirements without altering the core
modules of the DTD.
Q: Are there any limitations on modifying the DTD?
A: No. The DTD is in the public domain and may be
freely modified. However, most adopters of the DTD use it without
modification, in part to facilitate content exchange with other publishers
Q: Where can I find the authoritative version of the DTD?
A: At http://dtd.nlm.nih.gov/ and
The current version is 2.1. An FAQ with more information is available at
Q: What are the "blue" and "green" DTDs?
A: The NLM DTD is actually a suite of (now) three
DTDs. The DTD developers recognized that in the world of publishing, one
size would not fit all requirements, so two DTDs were developed from one
core set of modules: "blue" (publishing) and "green" (archiving). The
archiving DTD is less restrictive than the publishing DTD to meet the needs
of archiving, which are often different from publishing requirements. More
recently, NLM published a book version of the DTD in
early 2005 designed for use by book publishers.
Q: Why a DTD and not W3C XML Schema or RelaxNG?
A: W3C XML Schema and RelaxNG versions are available
from the NLM Web site. However, before jumping to use the Schema version,
we recommend you read the section Why not use
W3C XML Schema? in the NLM DTD FAQ hosted by NCBI.
Q: How is the DTD updated?
A: To keep the DTD relevant to the publishing and
archiving communities, NLM has created the XML Interchange Structure
Working Group. This group advises NLM on recommended changes in and/or
additions to the tagset. NLM has contracted with Mulberry Technologies
(of Rockville, MD) to act as Archiving and Interchange Tagset
Secretariat. The Secretariat will collect the feedback to be discussed by
the Working Group and will maintain the files and documentation. Feedback
may be posted at http://www.mulberrytech.com/DTD-Comment/CommentForm.html.
Q: Where did the NLM DTD come from?
A: The NLM Journal
Archiving and Interchange DTD Suite was co-authored by Inera Inc.,
Technologies, and NCBI.
The foundations of the DTD can be found in the E-Journal Archive DTD
Feasibility Study, a report prepared by Inera Inc. under a Mellon
Foundation grant for the Harvard University Libraries that surveyed the
DTDs of ten journal publishers.
Another useful Q&A; about the NLM Tag Suite is available on the Mulberry Technologies web site.