Upper Mapping and Binding Exchange Layer A lightweight, subject concept reference structure for the Web

Why OpenCyc?

The combination of the representativeness of UMBEL's subject concepts (the scope of the ontology) and their relationships (the structure of the backbone) is fundamental. These factors in turn express the functional capabilities of the system. The use of OpenCyc as the source basis for UMBEL is fundamental to these capabilities.

First Things First: The Importance of Context

A reference structure of almost any nature has value. A reference structure provides context, which in turn provides fixed points in the information space for relating distributed datasets to one another. Further, a reference structure of concepts has the further benefit of providing a logical reference structure for instances as well.

While Wikipedia is perhaps the most comprehensive collection of well-known instances, no single source can or will be complete in scope. Thus, many public and private sources of entities will emerge as reference hubs.

How do each of these rich instance sources relate to one another? What is the subject concept or topical basis by which they overlap or complement? What is the framework and graph structure of knowledge to give this information context?

These are the benefits brought by a structure of reference concepts, independent from the specifics of the reference structure itself.

Over time, it is likely that a few Web-based reference structures will emerge and compete and get supplemented by still further structures. This evolution is expected and natural and desirable in that it provides choice and options.

Alternative Approaches

Since the Web's inception, there have been various alternatives tried or in ascendance for organizing and bringing structure to Web content. Some of these may be too static and inflexible, others perhaps too arbitrary or parochial. All approaches to date have had little collective success.

Here is a summary of some of these alternate approaches:

• Existing library systems — Dewey Decimal Classification, Library of Congress, UDC and many other library classification schemes have been touted for the Web. None have enjoyed broad acceptance. Some reasons cited for this failure are physical books are very different from free digital bits; Web schema need to evolve quickly; and lack of stewards and curation
• Market share — at various times certain successful vendors have held temporary minor ascendance with content organizational frameworks, generally directory structures. Examples include About, Yahoo!, Open Directory Project (DMOZ), Northern Light, etc. Yet even at their peaks, market shares were low, external adoption was rare, scope was questioned and arbitrary, with interest in directories now nearly absent
• WordNet — though of strong interest and use to computational linguists, and quite popular for many content analyses, WordNet has seen little consumer or commercial interest. However, the synset structure and its coverage is extremely valuable for concept disambiguation, and therefore has a role in UMBEL (as it does in many other online systems)
• Standards efforts — some sporadic success and some notable failures have occurred in the standards arenas. Generally, the successful initiatives tend to be in close communities where there are clear financial benefits for adherence, such as in the exchange of financial or commerce data; broader and more ambitious efforts have tended to be less successful
• Professional organizations and associations — areas such a finance, pharmaceuticals, biologists, physicists and many bounded communities have enjoyed sporadic and sometimes notable success in developing and using domain-specific schema; none have yet transferred beyond their beginning boundaries to the broader Web
• Government initiatives — there are episodic successes for government-sponsored content organizational initiatives, mostly in metadata, controlled vocabularies and ontologies, often where contractors or suppliers may be compelled to comply. NIH's National Library of Medicine (and other NIH branches) have also seen significant domain successes, due to its foresight and its receptive biology, genetics and medical communities
• Upper ontologies — UMBEL investigated this area considerably in the early months of the project. Most of the upper ontologies have relatively sparse subject concept content, being geared to smaller, abstract-oriented upper structures. Some such as SUMO and DOLCE and now PROTON, have concerted initiatives to extend to middle- and domain-level ontologies. To date, penetration of these systems into general Web or commercial realms has been quite limited
• Wikipedia — a clear and phenomenal success, Wikipedia and related initiatives like Wikinvest and Wikicompany and scores more have proven to be a rich fount for named entities and article-length content, but not for the category and content organization structures in which that content is embedded. This is an area of keen academic and collective interest and it may still result is useful organizational schema as these popular wikis continue to evolve and mature. However, they have not yet done so, and while a rich source for entities and data, UMBEL decided to pass on their use for backbone structure at this time
• No collective structure — tagging or folksonomies or doing nothing have perhaps the greatest market share at present.

Since inception, the stated intent of the UMBEL project was to base its subject structure on extant systems. To minimize development time, the structure needed to be drawn from one of the categories above. Possible development of a de novo structure was rejected because of development time and the low probability of gaining acceptance in the face of so many competing alternatives.

Rationale for OpenCyc

The granddaddy of knowledge bases suitable to all human content and knowledge is Cyc. Because of its more than 20-year history, Cyc brings with it considerable strengths and some weaknesses.

Amongst all alternatives, Cyc rapidly emerged as the leading candidate. While its strengths warranted close attention, its weaknesses also suggested a considerable effort to overcome them. This combination compelled the need for a significant investigation and due diligence.

First, here are OpenCyc's strengths:

• Venerable and solid — through an estimated 1000 person-years of engineering and effort, the Cyc structure has been tested and refined through many projects and applications. While a few years back such groundings were unparalleled in the field, we are also now seeing some Internet-wide projects tap into the law of large numbers to get significant inputs of human labor. Cyc has also tapped this venue for ongoing expansion of its KB using the online FACTory game
• Community — there is a large community of Cyc users and supporters from academic, government, commercial and non-profit realms. Moreover, the formation of The Cyc Foundation has also served as a vehicle for tapping into volunteer effort as well
• Upgrade Path — OpenCyc has an upgrade path to the more capable ResearchCyc, full Cyc and the services of Cycorp
• Comprehensive — no existing system has the scope, breadth and coverage of human concepts to match that of Cyc (however, sources for named entities such as Wikipedia have recently passed Cyc in scope; see next section)
• Common sense — since its founding as a project and then backed by the standalone Cycorp, Cyc has set for itself both a more pragmatic but harder challenge than other knowledge systems. Cyc has set out to capture the common sense at the heart of human reasoning. This objective means codifying generally unstated logic and rules-of-thumb not unlike teaching a baby to walk and talk and read all of which are lengthy tasks of trial and error. However, as Cyc has gained this foundation, it has also led to a more solid basis for its reasoning and conceptual relationships
• Power and inference — ultimately the purpose of a knowledge base is to support reasoning and inference by computer when presented with a (often small) starting set of assertions or facts. Cyc has literally thousands of microtheories now governing its inference domains, giving it a scope and power unmatched by other systems. The importance of such reasoning is not the silly science fiction of autonomous intelligent robots, but as achievable aids to make connections, determine relationships and filter and order results
• Robust supporting capabilities — such knowledge base-wide capabilities can also be deeply leveraged in such areas as entity extraction, machine translation, natural language processing, risk analysis or one of the other dozens of specialty modules available in Cyc, and
• Free and open — last, but not least, is the fact that a mostly complete Cyc was released as a free and open source version in 2002. OpenCyc has now been downloaded more than 100,000 times and is in production use for many applications. Non-profits and academics can also obtain access to the full capabilities of the Cyc system through ResearchCyc. This open character is an absolute essential because leading Web applications and leading innovators of the Web eschew proprietary systems.

As first encountered, one impression of OpenCyc was that of a very solid structure, but somewhat obscured and deserving of a fresh cleaning.

The Decision and Implementation

Nearly five full months of due diligence were devoted to the question of the suitability of OpenCyc as the conceptual and relationship grounding for UMBEL.

On balance, OpenCyc’s benefits significantly outweighed its then weaknesses. This balance also stood considerably superior to all potential alternatives. An important factor through this deliberation was the commitment of Cycorp and The Cyc Foundation to the aims of UMBEL, and the willingness of those organizations to lend time and effort.

The decision was thus made in October 2007 to base UMBEL on OpenCyc and to undertake the (eventual) two person-years of effort to clean and vet the OpenCyc knowledge base for UMBEL’s purposes.

As discussed in the accompanying piece on UMBEL's role, the project has also made two pivotal decisions with respect to OpenCyc and its use:

1. All UMBEL subject concepts are based on existing concepts in OpenCyc. This means UMBEL inherits the proven structure and relationships extant in OpenCyc
2. No new subject concepts will be added to UMBEL that are not included in OpenCyc. This means that UMBEL's structure will not diverge from the structural relations already in OpenCyc. This decision preserves the use of UMBEL as a sort of contextual middleware between unstructured Web content and the inferential and tools infrastructure within OpenCyc (and beyond into ResearchCyc and Cyc for commercial purposes) and back again to the Web. We term this "round-tripping" and the capability is available for any of the 20,000 subject concepts vetted from OpenCyc within UMBEL.

Fortunately, in the intervening months, Cycorp has been responsive and made changes to the OpenCyc concept structure and its conversion to OWL in support of needs and observations brought forth by the UMBEL project. These provide comfort and a solid, adaptable structure for UMBEL moving forward.