Several years ago, in a copyright context, I came across a cartoon modeled on the Oracle at Delphi, the seat of ancient world prophecy. A disheveled and filthy traveler crawled toward the feet of a most contented-looking Oracle. The traveler had apparently come quite a distance, in all likelihood by foot, and while the Oracle appeared willing to listen, his interest in the traveler was reluctant, mild at best. Still, the traveler wanted the world's wisdom, at least as much as one can gain in a copyright context, and forcing what appeared to be his last breath begged of the Oracle to know, "What is Fair Use?" Since the cartoon was unfortunately of the one-frame variety, I personally never received the answer.
Such a cartoon could well be drawn about Digital Rights Management (DRM) in the emerging eBook environment. Here, however, our traveler friend would surely ask, "What is Interoperability?" The creator of our imagined cartoon would do well to ensure that this second cartoon were also of the one-frame variety so as to avoid having to answer that particular question. Such avoidance would place the Cartoon Creator in excellent company in the eBook world, and were I to offer a definitive answer here, the astute reader might conclude that I had rushed in where Oracles and Cartoon Creators fear to tread. Still, such questions must at least be approached if we are to gain an understanding of DRM in the emerging eBook environment. To that end, I address four initiatives that have, or soon must, grapple with such questions and issues: the Electronic Book Exchange Working Group (EBX) , the Open eBook Forum (OeBF), Digital Object Identifiers for eBooks (DOI-EB), and the recently published eBook Standards of the Association of American Publishers (AAP) .
Before proceeding, we need to keep two important points in mind. Firstly, although the term "eBook" serves an immediate marketing need in that it handily identifies something that many seem to understand, the very term "eBook" may be a misnomer. As the marketing focus shifts from the initial sale of an eBook to secondary uses and licenses involving more detailed rights transactions, it is very possible that the term "eBook" may be much less useful than it appears to be at the moment. Thus, we may come to speak of "ePublications." Secondly, what one considers to be "selling" an eBook may, in certain cases, be licensing. I have explored these points in greater depth elsewhere . For our immediate purposes, we must remember that eBooks are not yet fully fixed in commerce, or indeed in our minds, to anywhere near the extent that paper books are. Ironically, the very DRM technologies and processes that gave rise to notions of what eBooks are could begin to rob us of a definitive sense of what eBooks will come to be.
The AAP eBook Report
Several publishers and other interested parties contributed to the AAP eBook Report, and I would heartily recommend a review of that report for those interested in eBooks. The AAP eBook Report is actually three separate reports, and I comment on each throughout this article. They are:
These documents represent hundreds of hours of work by a variety of people in the publishing industry and are an excellent basis from which to address commercial and other needs of eBook environments.
AAP eBook Report: DRM for eBooks
"Digital Rights Management (DRM), the technologies, tools and process that protect intellectual property during digital content commerce," according to AAP's DRM for eBooks, "is a vital building block of the emerging electronic book (eBook) market. DRM creates an essential foundation of trust between authors and consumers that is a prerequisite for a robust market."  I do not take "robust market" in a solely or strictly commercial way, and although there is much focus on individual consumers, a "robust market" necessarily encompasses libraries, certainly digital libraries. The "DRM Core Concepts" section of the AAP Report is an excellent primer, and the "Publisher DRM Requirements" provides extraordinarily helpful guidelines to those building eBook standards or commercial eBook solutions. Let us dwell briefly on the section of the AAP DRM eBook Report entitled "DRM Interoperability".
AAP's DRM for eBooks: Interoperability
AAP defines Interoperability as "the condition achieved when two or more technical systems can exchange information directly in a way that is satisfactory to the users of the systems."  AAP acknowledges that eBook interoperability is not likely for some time [9, 10] and that consumers who expect eBooks to provide interoperability similar to paper books (which may be readily given, lent, or copied) may be "unpleasantly surprised"  to discover that various formats and reading devices are incompatible. Among the reasons AAP cites for these conditions are technology providers who "may be reluctant to adopt a different, standardized technology approach if this is viewed as weakening their patent protections."  AAP is not the first to observe the effect of patents on DRM standards making efforts [13, 14].
Within the eBook world, EBX was among the first to recognize the implications of patent rights on eBook DRM interoperability . EBX sought to craft a DRM eBook Specification that ensured consumers could "read any book, from any publisher on any device."  In fact, EBX specified that it would "…allow interoperability among different EBX client and server implementations, so that a server implemented by one vendor can authenticate a client implemented by a second vendor."  The EBX specification further asserted, "It is critical that the distribution and transfer protocols and the format of Vouchers and Credentials be standardized to ensure interoperability between [sic] publishers, distributors, booksellers, libraries, and consumers.  DRM eBook interoperability, while a stated goal of EBX, meant different things to different EBX members at different points in time. A colleague commented within an EBX context that "most technology providers fail to see value in the interoperability proposed by EBX. Why should a technology provider push for DRM interoperability when it could mean that other technology providers might benefit?"  To the extent we focused on DRM interoperability within EBX, we were unable to offer a compelling response to perfectly legitimate concerns about patent rights, issues that AAP aptly observes have been a factor in preventing DRM eBook interoperability. For now, such interoperability does not exist, and according to the AAP eBook Report, we are:
…in an environment clouded by multiple, incompatible technologies…Given (this) turbulence in the DRM technology market, it doesn't seem prudent to bet that any one DRM technology format  will emerge from the pack today and garner a commanding market share in the near term. A more reasonable approach, in the near term, is to diversify -- support all current DRM and content file formats and new ones as they appear. This approach is called "DRM pseudo-interoperability" (DPI)…(which) can maximize market opportunity size (because all reading devices become the market) and sidestep DRM interoperability issues. 
Kindly permit a brief digression having to do with the italics above: DRM technology format. DRM technology and format may be viewed distinctly, as they are two very different things. I sometimes hear it asserted that DRM Interoperability will be addressed by the Open eBook Publication Structure. However, this is not true, nor is it an objective of the OeBF Publication Structure Working Group. Rather, the Open eBook Publication Structure (available for public comment through 14 January 2001) addresses a different problem, that is:
allowing publishers to provide their content without having to reformat it for each reading system. The OeBF Publication Structure ensures that content can be viewed on any reading system which is OeB-compliant, so long as the owner of the reading system has the right to read the content on that reading system. 
The Publication Structure does not, and was not intended to address DRM interoperability. As noted on the OeBF web site, "DRM is an important issue for publishers and must be addressed by individual solution providers and by the industry in general. However, DRM is orthogonal to the creation of an open rich content encoding scheme, which is what the (OeBF Publication Structure) Specification is all about."  My colleague makes another interesting observation for which I cannot take credit: "The OeBF Publication Structure is widely acceptable because it does not threaten any single vendor's value proposition."  My colleague's observation causes me to wonder whether EBX's attempt, or indeed any attempt, to create full-fledged DRM eBook interoperability is, for now at least, a bridge too far.
In attempting to craft some sort of DRM eBook interoperability, the approach of OeBF's Publication Structure might well be a useful guide. Is there a type of interoperability that can facilitate DRM requirements along the eBook value chain while also not threatening, or even appearing to threaten, perfectly legitimate patent rights, other intellectual property rights and corresponding commercial interests? Two immediate possibilities come to mind.
The first, noted in the AAP DRM eBook Report, and quite familiar to participants in EBX, is a common rights language for eBooks. There appear to be two candidates at the moment: eXtensible Rights Markup Language (XrML) . and Open Digital Rights Language (ODRL)  AAP notes that "a common DRM language will make it easier for content providers to supply content for any DRM system. " My colleague again provides guidance when he suggests that "even with different DRM implementations, technology providers can also cooperate -- they can agree to rights messaging standards." 
The second possibility for a solution to facilitate eBook requirements is interoperability -- not of DRM or of content -- but of metadata. Before suggesting how interoperability of data bears on DRM in the emerging eBook environment, permit me briefly to review two additional topics addressed by the AAP eBook report -- metadata and numbering.
EBook Metadata and Numbering
"The publishing industry is built from a collection of disparate databases, many of which contain very similar data but few of which can directly interoperate with each other," according to John Erickson [28, 29] . AAP notes that "without (metadata) standards, in order to track, find, and sell or purchase an eBook, (parties) bear the cost of inefficient mechanisms of entering and communicating metadata…."  AAP states as an assumption that the existing ONIX International Standard (ONIX)  "will be the baseline for all Metadata standards recommendations."  AAP defines metadata as "data about data"  and also provides a second worthwhile description of metadata as "factual information that identifies or describes Content and includes all such information except the content itself."  Metadata accompanying an eBook enables us more completely to understand an eBook for commercial and other purposes. Most of the information on the title page of a book, for example, is metadata. The AAP Metadata Report makes particularly cogent arguments for the need to standardize certain eBook metadata (e.g., for discovery purposes) while ensuring that other metadata can remain private and unseen by the unauthorized. Ensuring that all participants in the eBook value chain have a common understanding of eBook metadata is essential if eBook content is to be described efficiently and effectively, as is the AAP's stated goal. Such standardized metadata, however, could also be the foundation for an eBook system of interoperable metadata that need not, and in all likelihood would not, threaten "any single vendor's value proposition." Such interoperability of metadata could well begin to address the concerns AAP outlines with regard to the dearth of DRM interoperability, perhaps providing a step beyond the DRM pseudo-interoperability (DPI) AAP describes, or, at the very least, facilitating it. Concepts of such interoperability of metadata will be familiar to those acquainted with the intellectual rigor of Indecs , developed through the efforts of Mark Bide and Godfrey Rust, who have made clear that "electronic trading depends to a far greater extent than traditional commerce on the way in which things are identified (whether they are people, stuff or deals) and the terms in which they are described, that is, metadata."  Indecs, of course, did not focus on eBooks, but it might provide guidance to those involved in eBook undertakings who would like to see some kind of interoperability develop.
AAP's eBook Numbering Report recommends "that publishers implement a new number standard based on Digital Object Identifiers (DOIs) for all eBooks (and) use the DOI in conjunction with the ISBN (or EAN, U.P.C. ISSN) for legacy purposes."  The International DOI Foundation (IDF) developed the DOI, an identification system for intellectual property in the digital environment.  Metadata associated with a DOI "can express relationships; and it can work with other metadata from other sources to construct services and transactions (by conforming to a standard way of using metadata -- e.g., by expressing the context in which a piece of intellectual property is being used). This enables the construction of predictable, automated transactions." 
Toward eBook Interoperability of a Sort 
Two complimentary initiatives, one within the Open eBook Forum and a second within the International DOI Foundation, could well provide the eBook world with the beginnings of interoperability of eBook metadata, and thus provide an avenue toward the DRM interoperability sought by the authors of the AAP eBook Report. Within OeBF, working groups for metadata and identifiers are in the process of outlining detailed requirements as a foundation, perhaps, to developing eBook standards. OeBF is not attempting to reinvent metadata and identifier systems already in place. The requirements developed by such undertakings will inform not only possible standards development within, or adoption by, OeBF but could also inform the second important initiative now under way.
As noted in the AAP eBook Report, DOI provides a framework for managing intellectual content, for linking customers with content suppliers, for facilitating electronic commerce, and enabling automated copyright management for all types of media. (The DOI is an implementation of the CNRI Handle System® in which the term "DOI" is used to describe the identifiers .) The IDF recently established Digital Object Identifier for e-Books (DOI-EB), one of the purposes of which is to develop technical demonstrations and prototypes for the use of DOI with eBooks based on publisher requirements, many of which appear in all three sections of the AAP eBook report. Might the combination of requirements established within OeBF and elsewhere, combined with the prototype work DOI-EB begins in the first quarter of 2001, provide a foundation for interoperability of eBook metadata? Perhaps so.
Persistent readers might recall the imagined cartoon about Digital Rights Management (DRM) in the emerging eBook environment and my admonition that the creator of such a cartoon would do well to avoid answering, "What is Interoperability?" The eBook interoperability envisioned here -- that of eBook metadata based on DOI -- is not the same as the DRM interoperability described in the AAP eBook Report. For the most part, such DRM interoperability does not exist among technology solutions providers. However, interoperability of eBook metadata based on DOI is a possible practical step toward DRM interoperability in that it will not "threaten any single vendor's value proposition." The elements of this approach are to be found within the recommendations of the AAP eBook Report itself, namely standardized metadata and use of DOI. To bring such interoperability of eBook metadata to fruition, eBook requirements and, perhaps, ultimately eBook standards developed by OeBF as well as the prototypes based on such requirements to be developed by DOI-EB might well cause a future cartoon creator to add a second frame to our imagined cartoon and tentatively, at least, offer an answer to "What is Interoperability?" This time, the Oracle might well point to standardized eBook metadata and unique identifiers as our best practical guide to DRM interoperability in the emerging eBook environment.
Notes and References
Notes and References
 No discussion of EBX can proceed without acknowledging the enormous contributions of Glassbook, recently acquired by Adobe, and particularly the time and effort devoted by Tom Diaz, Bob Mathews, and the rest of the Glassbook team. In December 2000 the EBX membership voted to merge into the Open eBook Forum (OeBF) as of 1 February 2001. Back to the text of the article.
 AAP commissioned Andersen Consulting to assist in producing a report on electronic books. It is sometimes referred to as "The Andersen Report." However, I refer to it in this article as the "AAP eBook Report." It contains three sections, one on Digital Rights Management (DRM), one on metadata, and one on numbering, and it is available at <http://www.publishers.org>. Back to the text of the article.
 In a forthcoming article in Publishing Research Quarterly entitled "Digital Object Identifiers for eBooks: What Are We Identifying?", I first addressed "What is an ebook?" and the sales/licensing distinction in a presentation to the International Rights Directors' Meeting at the Frankfurt Book Fair, October 2000. Back to the text of the article.
 Digital Rights Management for eBooks: Publisher Requirements, version 1.0 Association of American Publishers, New York, NY and Washington, D.C. USA, November 2000 (available at http://www.publishers.org/home/drm.pdf). Back to the text of the article.
 Numbering Standards for eBooks, version 1.0, Association of American Publishers, New York, NY and Washington, D.C. USA, November 2000. Back to the text of the article.
 Metadata Standards for eBooks, version 1.0 Association of American Publishers, New York, NY and Washington, D.C. USA, November 2000. Back to the text of the article.
 AAP DRM Report at 6. Back to the text of the article.
 Ibid at 57. Back to the text of the article.
 "DRM standards will need to enable interoperability that will drive robust market growth. While there are some nascent efforts at standardization underway, DRM-related technologies are likely to remain nonstandard for some time because companies are currently pursuing incompatible proprietary solutions." Back to the text of the article.
 Ibid at 6. Back to the text of the article.
 Ibid at 25. Back to the text of the article.
 Ibid at 26. Back to the text of the article.
 For especially thorough treatments of how patent rights and Digital Rights Management implicate one another, see the various works of the Motion Picture Experts Group (MPEG). Such work is unfortunately beyond the scope of this article. I am particularly indebted to Mr. Douglas Armati of Intertrust Technologies <http://www.intertrust.com> for his outstanding descriptions of MPEG's work. Back to the text of the article.
 See also Schull, Jonathan, Presentation at OeBF Meeting, New York, NY USA, June 2000. Dr. Schull is Founder and Chief Scientist of Digital Goods <http://www.digitalgoods.com>, formerly Softlock. Back to the text of the article.
 See <http://www.ebxwg.org> and the EBX Membership Agreement in particular, provisions of which encouraged EBX members (largely technology companies) to disclose the extent to which EBX specifications implicated their patent rights and to make clear the terms under which they would license their rights, if at all. These provisions were much discussed within EBX, particularly when the subject of DRM eBook interoperability arose. The EBX patent disclosure provisions were never invoked, and harmonization of patent rights vis-à-vis eBook interoperability was largely an academic matter within EBX. Now that EBX has voted to merge into the Open eBook Forum, the provisions of the EBX membership agreement as to patents are largely moot. I intend no criticism of EBX processes that in fact had my full support. Of course, I was fortunate enough to represent an organization that held no patent rights in the area, so the question was, in all events, relatively easy for me. Back to the text of the article.
 The Electronic Book Exchange System, version 0.8, Book Industry Study Group, New York, NY USA, July 2000 at 8. Back to the text of the article.
 Ibid at 38. Back to the text of the article.
 Ibid at 47. Back to the text of the article.
 Communication from an anonymous colleague, 4 December 2000. Back to the text of the article.
 The italics are mine. Back to the text of the article.
 AAP DRM Report at 28. Back to the text of the article.
 Ibid. Back to the text of the article.
 Communication from an anonymous colleague, 4 December 2000. Back to the text of the article.
 Private communication from an anonymous colleague, 4 December 2000. Back to the text of the article.
 Erickson, John. The Role of Metadata Supply Chains in DOI-Based, Value-Added Services. ICSTI Forum <http://www.icsti.org/icsti/forum/fo9904.html>, Quarterly Newsletter of the International Council for Scientific and Technical Information, No. 30, April 1999. Back to the text of the article.
 Dr. Erickson coined the phrase, "Metadata is the lifeblood of e-commerce." Back to the text of the article.
 AAP DRM Metadata Report at 7. Back to the text of the article.
 ONIX is published and maintained by Editeur, <http://www.editeur.org>. As noted on Editeur's web site, "The goal (of ONIX) is to standardize the transmitting of (book) product information so that wholesalers, retailers and others in the supply chain will all be able to accept information that is transferred electronically in ONIX International format." Back to the text of the article.
 Ibid at 6. Back to the text of the article.
 Ibid at 41. Back to the text of the article.
 Ibid at 35. Back to the text of the article.
 AAP eBook Numbering Standards at 7. Back to the text of the article.
 See Bide, Mark, In Search of the Unicorn, The Digital Object Identifier from a User Perspective, BNBRF Report 89, Book Industry Communications, London, February 1998 (available at http://www.bic.org.uk/unicorn2.pdf). See also Bernstein, Paula, DOI: A New Identifier for Digital Content. Searcher: The Magazine for Database Professionals, Vol. 6, No. 1, Jan. 1998 (available at http://www.infotoday.com/searcher/jan98/story4.htm). See also The DOI Handbook, version 0.5.1, The International DOI Foundation, Washington, D.C. USA and Geneva, Switzerland, September 2000 (available at http://www.doi.org/handbook_2000/index.html). Back to the text of the article.
 Paskin, Norman, Digital Object Identifier: implementing a standard digital identifier as the key to effective digital rights management, The International DOI Foundation, Kidlington, Oxfordshire, United Kingdom, 2000 at 3 (available at http://www.doi.org/doi_presentations/aprilpaper.pdf). Back to the text of the article.
 John Erickson of HP Labs advocates interoperability through vocubularies and messaging standards. See Erickson, John, "Toward an Open Rights Management Interoperaability Framework, <http://www.oasis-open.org/cover/ericksonRT19990624.pdf>. Back to the text of the article.
 The Corporation for National Research Initiatives, Handle System <