Posted:August 23, 2009

Snake Shedding

In the Future, All of us May be SysAdmins

OK, well, I just finished moving and upgrading some dozen Web sites and wikis, including this one — my main blog — over the weekend, from fixed stuff to the “clouds“. Believe you me, there were some pretty massive changes required.

For someone like me who is relatively clueless about such things, the process has been interesting (to say the least).

It seems like our modern era either involves moving digital things or converting digital things. As for moving, we all experience that laptop or hard drive dying, and then the move. (The Death of a Laptop actually happened to my wife this past week.) But it also is changing providers and venues — what caused me to move all of these Web sites.

Shedding the Snake Skin

So, the mainstream digital age has existed for what, now, some 40 years? How many data formats have we transitioned (ASCII, EBCDIC, UTF-8, an immense number)? And, how many systems and environments have we transitioned?

At the risk of dating myself, when I was in college we still used slide rules; truly the end of an era. Just a year or two later everyone transitioned to having TI or HP calculators, some they wore on their hips like some PDAs and cell phones today.

I won’t bore everyone with my own transition from my first computer (an HP 9100 with 4K RAM and program listings on cash register tapes) through many others including a DEC Rainbow PC with CP/M (a beauty!). For many years, as we moved into the PC era and IBM legitimized the shift, every computer I bought seemed to cost about $3000. Each one was more capable, etc., but they all cost the same.

And, then, about the late 1990s, that changed. In fact, my last capable desktop machine cost way south of $1000.

But, I digress.

What has been the real constant across these decades has been system and data migration. Granted, many of the docs and many of the systems in my own experience from 30 yrs ago have no relevance today (god, do I miss WordPerfect with its embedded, editable codes!), but actually an important minor portion do.

For these, I need to move both apps and data (with readable formats) for each generational transition.

I know that organizations, like the Library of Congress in its NDIIPP program, need to worry about digital preservation, potentially for millenia. These are worthwhile concerns.

But, from my own more prosaic standpoint, I see this issue with my own lens and own bas relief. I am constantly moving apps and data, each transition much like a snake shedding its skin.

It makes one wonder about the effort and process by which the entire meaningful cultural history of our species continues to adapt and transition forward.

Getting Back to Real

Hmmm. All of us have seen these transitions and the loss of productivity they bring in that shift. (Some might argue that the lack of productivity gains from computers until this decade was due to such transitions, which at least now with the Web we see a more common migration framework.)

I think we have no choice but to transition to the next latest and greatest as it emerges. Automated means at acceptable cost for doing such transitions will also be attractive.

But the real point, I think, is that such transitions are inevitable. Faster apps: Check! Better apps: Check! Easier data exchange: Check!!

Living with transition thus becomes a clear constant for all us as we move forward. And, part of that is accepting downtime to screw around moving the keepable old to the potentially useful new.

After this weekend, I’m now ready for a couple of days off before the real work week begins (yeah, right, keep dreaming).

Posted:August 17, 2009

Structured Dynamics LLC

Ontology Best Practices for Data-driven Applications: Part 4

The earlier portions of this occasional series have set the groundwork for the role of ontologies in data-driven applications. In this part, I address many of the current misconceptions of what ontologies do or do not do. For, as practiced by Structured Dynamics, our adaptive TBox-level ontologies [1] are definitely not your grandfather’s Oldsmobile.

To share the punch line early, these modern ontologies are fast to develop, easy to change, adaptive to new knowledge and perceptions, robust and flexible. Indeed, it is the structure and nature of these adaptive ontologies that is the heart and secret of data-driven applications.

Any knowledge worker can understand and refine the organization and relationship of information via these structures. And, most importantly, the resulting ontologies are sufficient to drive the generic applications that are based on them. Focusing on data and structure now becomes the emphasis. We can now remove prior bottlenecks arising from the need to customize applications, configure report writers, or wait for IT to generate SQL queries.

But, not all ontologies are created equally and not all practitioners explain or see them in the same way. The purpose of this Part 4 in our series is to present many of the misconceptions, offering a score of takeaway messages for how properly considered and constructed ontologies can achieve these benefits.

Misconception: No ‘Big Bang’ Needed

To be sure, there are many very large and comprehensive ontologies. Some are focused on specific applications or domains; some are general; and some are the result of large and well-funded projects [2]. I am not arguing that such efforts do not have their role and place. But when viewed as exemplars or notable cases, these complex and comprehensive ontologies can create a misconception that such a scope is an imperative of proper ontology design.

I believe quite the opposite to be true.

An incredible strength of RDF and OWL ontologies is that they can be built incrementally. So long as additions are coherent with some degree of self-consistency in terms of the world view in which they are represented, any of an ontology’s constituent concepts, predicates or entities and datasets can be added and enhanced as needed. This makes ontologies a very different cat from relational schema, which are notoriously brittle with expensive re-architecting required anytime that scope or schema change.

Enterprise consultants that advocate “big” upfront ontology development efforts are doing their clients a massive disservice. They are also cynically playing on the experience with relational schema. As soon as the marketplace begins to realize that ontologies are incredibly plastic and malleable, this huge advantage of ontologies over the relational model for data federation will ring clear.

Takeaway Message #1: Ontologies can (and should!) start small.

Takeaway Message #2: Ontologies can (and should!) grow incrementally.

Misconception: No ‘One Ring to Rule Them All’

As a practitioner, two of the most boring arguments I hear are: Ontology X is better than other ontologies and here is why; and, Use of some reference or upper ontology reduces choice and freedom. Both arguments are somewhat grounded in the ‘one ring to rule them all’ mindset — though coming from opposing perspectives — that I think fundamentally misreads the role and purpose of ontologies.

Ontologies provide an organizing context for relating disparate information together and for making meaningful inferences. Without such a framework these purposes can not be achieved. But the framework itself is a function of the world view, context and domain scope at hand. As a result, there is only context, and not some single, universal “truth.” As they say, it all depends.

The trick, then, to properly designed ontologies is to maintain internal coherence and self-consistency [3]. When done, it is then possible to relate disparate information and data to other data and to make intelligent business inferences.

So, the use of an ontology does not limit freedom. It sets the context for making connections and setting relations. And, as long as it is coherent, the “correct” ontology is the one that best captures the scope and domain at hand. Arguing for one ontology v another is wasted energy. Just get on with it.

Takeaway Message #3: There is no single “truth”, only coherence and relevant context.

Misconception: No Such Thing as an ‘Ontological Commitment’

One of the more pernicious ideas promoted by some practitioners or advocates is the idea of ‘ontological commitment.’ Though some definitions are relatively benign, such as the one offered by the Stanford Knowledge Systems Laboratory (KSL) [4], the unfortunate use of the term “commitment” implies permanence and immutability. (In fact, most definitions of this phrase affirm this interpretation.)

This is really unfortunate, as it again tends to reinforce the inaccurate analogies with brittle and inflexible relational schema.

A much better way to view ontologies is not as a “commitment,” but as a vehicle for developing a common world view within the enterprise. Under this viewpoint, ontology development is somewhat analogous to master data management (MDM) or corporate taxonomies [5]. In this broader sense, then, ontology development can become a means for developing and refining a common language within the enterprise through consensual or community processes.

For the reasons as noted above, as language or conceptual relationships or understandings change, so can the vocabulary or structural character of the ontology change. There is no “lock in”; there is no “commitment”. As long as it is coherent, the ontology can morph to reflect the scope and understandings of the current snapshot in time.

This flexibility results from the fact that the ontologies, properly constructed, can drive a generic set of tools and applications that express themselves based on the underlying structure and vocabulary within those ontologies. The ontologies can thus change at will without any adverse effects whatsoever on the applications based on them.

This data-driven aspect, as noted throughout this series, is quite different from any prior paradigm. So, under this view ontologies have considerably more focus and importance than even some of the strongest ontology advocates claim, yet paradoxically without the theoretical bloat or heaviness many purport. Like human languages, our language and concepts within ontologies change as our world and perceptions change.

Takeaway Message #4: There is no “lock-in” with ontologies; they may be modified and changed at will.

Takeaway Message #5: Like corporate taxonomies or MDM, ontologies provide a framework for enterprises to develop internally consistent common languages or vocabularies.

Takeaway Message #6: Unlike corporate taxonomies or MDM, ontologies can drive directly generic tools and applications.

Misconception: No Need for Completeness or Comprehensiveness

Ontology development is not some imperative for conceptual “truth”; rather, it is a very adaptable means for stating, testing and refining stuff. Like agile development for software, this refining approach can and should proceed incrementally. Too often ontology efforts get caught like deer in the headlights awaiting some “completeness” threshold before release.

One means to promote this approach is to tackle single datasets or data stores individually before moving on. Having a sense of the eventual scope is useful, of course. But it is also quite acceptable to only fill out those portions of the structure with data available at hand.

These observations reflect a prejudice to action and release, rather than theory. If mistakes are made, fine: simply correct them.

Takeaway Message #7: Understand the full scope, but only build out for the data in hand.

Misconception: No Need for Predicate Bloat

It is advisable to keep relationships (predicates) simple at first. Because, again, like human languages, keeping the verbs simple until fluency is gained is another best practice.

While all of us can see nuances and subtleties heading into a project, trying to accommodate those predicates (relationships) at the outset can introduce unnecessary complexity. This is not an advocacy in any way for inaccurate predicates, but perhaps to err on the side of the general and broader at first.

For organizations familiar with taxonomies, the SKOS vocabulary is a good focus, and there are some other standard starting ontologies that provide a good starting base of predicates [6]. Then, as you work with your data and its requirements, you can later expand to more sophisticated relationships.

In taking this approach you will still see immediate benefits due to the value of connected data through the Linked Data Law [7]. But, at the same time, you will be embracing a simpler language to start and then gain fluency.

Takeaway Message #8: Use simple, well-defined and documented predicates (properties or attributes).

Takeaway Message #9: You are building a common language for the enterprise; do so purposefully.

Misconception: No Need for Expensive Up-front Engineering

All of these observations lead to the conclusion that upfront ontology development need not be expensive. Any consultant selling six-figure ontology development to businesses ought to be seriously challenged. Start small and focused. Frankly, a simple spreadsheet taxonomy or quick conversion of existing XML or metadata or vocabulary standards is A-OK to get started.

Takeaway Message #10: Start small with stakeholders to build acceptance and best practices.

Takeaway Message #11: Start immediately to organize and federate existing information.

Misconception: No Need to Reinvent the Wheel

While it is true that the usefulness of ontologies as advocated by Structured Dynamics is greater than other constructs, these ontologies still just represent a more capable representation of knowledge structures that have been around in various other forms for years. For decades enterprises have created schema, taxonomies, controlled vocabularies, standards, and other knowledge structures that represent untold time, dollars and effort. It would be a waste to not fully leverage these sunk investments.

Further, many ontologies and interoperable structures also exist external to the enterprise, many open source and freely available. And, even if not all are already in proper ontological form, like internal structures these other constructs can be relatively easily leveraged and turned into ontology-ready form.

So, what we are doing with adaptive ontologies is not creating new structures or new representatiions from scratch, but leveraging the expressions of our current world views. These have been hard-earned, codified over years of effort, and are legacy expressions of the enterprise’s knowledge base.

In this vein, then, there is already much richness available to any organization upon which to embark on their ontology efforts. Use them, and gain great leverage.

Takeaway Message #12: Aggressively mine and re-use existing knowledge and structure.

Takeaway Message #13: Leverage and re-use appropriate portions of the “best” existing, external ontologies.

Misconception: No Requirement to Displace Existing Assets

Continuing in this same spirit, it is a mistake to see adaptive ontologies and the associated systems advocated by Structured Dynamics as a replacement for existing data assets. Rather, the idea and advantage is to keep data records in situ as much as possible. These are already performing investments that can be left largely as is. The role of the adaptive ontologies is to act as a federation layer that bridges across these existing assets.

This leverage of existing data assets can occur via the architecture of the system (generally Web-oriented architecture [8]) and a design of the data system and structures providing proper allocation between the ABox and TBox [1].

All of this maintaining of existing assets is aided by the ability to convert in-place data to ontology-ready RDF form. This is a separate topic in its own right and one I discuss elsewhere [9]. There is also a need to make sure that the attributes of the underlying instance records (generally, the columns within a relational table) are also properly modeled within the adaptive ontology. This is part of the best practices guidelines.

Of course, how much of the existing assets can be leveraged “as is” and what degree of modification or conversion might be necessary needs to be evaluated on a case-by-case basis. Generally, however, these mappings can be pretty straightforward and leave in place all existing hardware, software and administration procedures.

Takeaway Message #14: Leverage your existing databases as rich sources of instance records (“ABox”).

Takeaway Message #15: Explicitly design your TBox ontologies to be an interoperability layer over these existing record stores.

Takeaway Message #16: Reconcile the semantics across the enterprise’s data stores at this interoperable TBox layer.

Misconception: No Closed World Assumptions

A closed world assumption holds that any statement that is not known to be true is false. Most enterprise database and transaction systems are based on this premise. It works well where there is complete coverage of the entities within a knowledge base, such as the enumeration of all customers or all products of an enterprise.

Yet, in the real (“open”) world there is no guarantee or likelihood of complete coverage. Thus, under an open world assumption the lack of a given assertion or fact being available neither implies whether that possible assertion is true or false: it simply is not known.

An open world assumption is one of the key factors for enabing adaptive ontologies to grow incrementally. It is also the basis for enabling linkage to external (and surely incomplete) datasets.

In fact, systems designed around the open world assumption can still achieve closed world reasoning where the circumstances and completeness of the knowledge base permit. But, rather than being a logical outcome of the framework, such completeness axioms need to be explicitly stated. Thus, open world systems can achieve the same ends as closed ones where applicable, but with greater flexibility and extensibility.

Takeaway Message #17: No enterprise is an island; design according to the open world assumption.

Misconception: No Restriction to a Dedicated Priesthood

Consultants make their money and academics their reputation by often making things more obscure and jargon-laden than they need be. Ontologies — heck, even the name itself — is no exception.

But what we have laid out as general guidelines herein and their reduction to practice does not require a priesthood. Sure, there are some things to learn and some practices to follow, but these are certainly easier to understand and master than, say, a programming or scripting language. Adaptive ontologies done right can be a participatory activity within most any organization.

Some guidance and mentoring would certainly be helpful. Make sure to pick the right individuals that truly embrace these perspectives.

Also helpful would the assistance of groups skilled in team building and group participation [10].

Takeaway Message #18: Engage all knowledge stakeholders in ontology creation, review and refinement.

Takeaway Message #19: Use selected ontology engineers to help ensure consistency, but not necessarily structure.

Design for Data-driven Apps

The above addresses misconceptions related to how the market perceives current ontologies or how some advocates push the concept. But there are some unique perspectives that Structured Dynamics brings to ontology development specific to the purpose of data-driven applications. From a best practices standpoint, these considerations should also be included.

In order to properly “drive” applications and user interfaces and reports, specific design attention needs to be give to:

  • Linked data, and the use and accessibility of URIs as resource identifiers
  • Context- and instance-sensitive data display, including templates, and
  • Driving user interfaces via the inclusion of preferred and alternate labels in the ontology.

Of course, there are other considerations that come to bear. But these lend themselves to some rather simple checklist guidelines during ontology development and maintenance.

Takeaway Message #20: Follow some relatively straightforward best practices to gain all of the advantanges of adaptive ontologies.

This post is part of an occasional AI3 series on ontology best practices.

[1] We use the reference to “TBox” in accordance with our working definition for description logics:

"Description logics and their semantics traditionally split concepts and their relationships from the different treatment of instances and their attributes and roles, expressed as fact assertions. The concept split is known as the TBox (for terminological knowledge, the basis for T in TBox) and represents the schema or taxonomy of the domain at hand. The TBox is the structural and intensional component of conceptual relationships. The second split of instances is known as the ABox (for assertions, the basis for A in ABox) and describes the attributes of instances (and individuals), the roles between instances, and other assertions about instances regarding their class membership with the TBox concepts."
[2] Chemicals, petroleum and pharmaceuticals are renowned for large-scale, vertical ontologies. Examples of general or upper-level ontologies include the Suggested Upper Merged Ontology (SUMO), the Descriptive Ontology for Linguistic and Cognitive Engineering (DOLCE), PROTON, Cyc, BFO (Basic Formal Ontology) and UMBEL (Upper Mapping and Binding Exchange Layer). Many of the large exemplar ontology projects are funded under EU auspices; see write-ups for the 7th ICT (Information and Communications Technologies) program for the EU and prior ICT projects for more information.
[3] See, for example, my posting on When is Content Coherent? from about one year ago.
[4] See, for example, the Stanford KSL discussion on What is an Ontology? One part of that document explains ontological commitments as “agreements to use the shared vocabulary in a coherent and consistent manner,” which is benign enough. But other discussions and venues imply much more viz. the “commitment” term. This same Stanford source is also a useful for general philosophical discussions of ontologies.
[5] With respect to corporate taxonomies, see for example, Trish O’Kane, “United by a Common Language: Developing a Corporate Taxonomy“. Information Management Journal. FindArticles.com. 15 Aug, 2009. http://findarticles.com/p/articles/mi_qa3937/is_200607/ai_n17176092/.
[6] Some of the standard starting vocabularies that Structured Dynamics recommends include many of the ones listed on this useful ontology table from Freebase, and specifically include Dublin Core, Friend-Of-A-Friend (FOAF), GeoNames, SIOC, SKOS, RDF Schema, XML Schema, OWL, UMBEL, and BIBO. These are typically supplemented with domain-specific ontologies appropriate to the scope at hand.
[7] The Linked Data Law states the value of a linked data network is proportional to the square of the number of links between data objects. It is a derivative of Metcalfe's law, which states that the value of a telecommunications network is proportional to the square of the number of users of the system (n2), where the linkages between users (nodes) exist by definition. For information bases, the data objects are the nodes. Linked data works to add the connections between the nodes. This concept was first presented in ago in What is Linked Data? and then formalized in [9].
[8] In WOA, discrete functions are packaged into modular and shareable elements (services), then made available in a distributed and loosely coupled manner using Representational State Transfer. REST provides principles for how resources are defined and used with simple interfaces without additional messaging layers. REST is a foundation to the HTTP protocol and a key reason for the success and scalability of the Web.
[9] See further my posting, Structure the World.
[10] As a matter of full disclosure, Structured Dynamics does not have expertise nor strengths in these areas.
Posted:August 3, 2009

The "Blue Marble": The Earth seen from Apollo 17.jpg from Wikipedia.org

Multiple Techniques and Data Structs can Make the Vision a Reality

Linked data and subject and domain ontologies provide the organizing framework. Techniques for converting, tagging and authoring structure provide the content. In combination, we now have in hand the necessary pieces to enable all of us to “structure the World.”

In this vision, the nature of the links or connections between data need not be complicated to gain tremendous benefit. Similar to Metcalfe’s Law for the increasing value of networks as more nodes (users) get added, adding connections to existing data is a powerful force multiplier.

We can call this the Linked Data Law: the value of a linked data network is proportional to the square of the number of links between data objects [1]. Further, if we are purposeful to include connective links where appropriate as we add more data (that is, nodes), this multiplier effect becomes even stronger.

Structured Dynamics is dedicated to help make this prospect real. Meaningful progress in doing so requires only a relatively few moving parts or techniques. Yet, because we sometimes bounce from talking or focusing on one part versus the others, we can lose context or sight of the overarching vision. The purpose of this article is to re-set and calibrate that overall vision.

The Vision: Data Federation of Any Desired Content

The vision is to get all data and information to interoperate, regardless of legacy or form. Much of this data is already structured, either from databases or simpler forms of data structs. Some of this information is unstructured or semi-structured, requiring extraction and tagging techniques. And new information is being constantly generated, which warrants better means to author and stage for interchange and interoperability.

No matter the provenance, all information has context and scope. As a chunk from here, and a piece from there, gets added to our linked data mix, having means to characterize what that data is about and how it can be meaningfully inter-related becomes crucial. Sometimes these contexts are informed by existing schema; sometimes they are not. But, in any case, it is the role of ontologies to both position these datasets into an “aboutness” framework and to help guide how the data can be described and related to other data. This part of the vision invokes semantics and coherent structures (schema or ontologies) for positioning and mapping datasets to one another.

As both the means for representing any extant data format and as the means for describing these conceptual relationships or schema, RDF provides the canonical data model. A single target representation and common data model also means we can develop and design a smaller universe of tools to operate and provide functionality over all of this data. Indeed, because our RDF data model and its ontologies are so richly structured, we can design our tools with generic functionality, the specific operation and expression of which is based on the inherent structure within the data and its relationships. This vision of data-driven apps leads to extreme leverage, incredible flexibility, and inherent “meshup” capabilities for tools.

Further, because we use Web identifiers (URIs) for our data and concepts and because we expose and access this linked data via the Web, we use the proven and scalable architectures of the Web itself for how we design our systems. This Web-oriented architecture (WOA) provides a completely decentralized and loosely coupled deployment model that can work ranging from public and open to private and proprietary, applicable to data and participants alike.

From the outset, it is essential to recognize that thousands of contributors are enabling this vision. So, while Structured Dynamics naturally uses its own tools and techniques to flesh out the various parts of this vision below, realize there are many players and many tools from which to choose [2]. For that is another aspect of this vision that is quite powerful: providing choice and avoiding lock-in.

RDF: The Canonical Data Model

The core construct — or fulcrum, if you will — of the vision is the RDF (Resource Description Framework) data model [3]. I have written elsewhere on the Advantages and Myths of RDF, which explains more precisely the advantages of that model. RDF provides a common data model to which any external format or schema can be converted and represented. It also provides a logic model and basis for building vocabularies that can inform and drive generic tools.

In the context of data interoperability, a critical premise is that a single, canonical data model is highly desirable. Why?

Simply because of 2N v N2. That is, a single reference (“canon”) structure means that fewer tool variants and converters need be developed to talk to the myriad of data formats in the wild. With a canonical data model, talking to external sources and formats (N) only requires converters to and from the canonical form (2N). Without a canonical model, the combinatorial explosion of required format converters becomes N2 [4].

Note, in general, such a canonical data model merely represents the agreed-upon internal representation. It need not affect data transfer formats. Indeed, in many cases, data systems employ quite different internal data models from what is used for data exchange. Many, in fact, have two or three favored flavors of data exchange such as XML, JSON or the like. More on this is discussed in a section below.

As this diagram shows, then, we have a single internal representation that is the target for all data and format converters and upon which all tools operate. These tools are themselves expressed as Web services so that they may be distributed and conform to general WOA guidelines. In addition, there may be multiple external “hubs” that represent alternative data models or formats or schema conversions (say, for relational databases). So long as we have converters between these alternate “hubs” and our canonical RDF form we can allow a thousand flowers to bloom:

Other canonical forms could be advocated. Yet RDF has the logical basis to represent any data form and any schema or conceptual structure. It is based on a robust set of open standards and languages and tools. It may be serialized in many formats. It can be grounded in description logics and, in appropriate forms, reasoned over and expressed in vocabularies and schema suitable for the most complex of conceptual structures and semantics. RDF is the data model explicitly designed for the Web, the clear global information basis for the foreseeable future.

For more than 30 years — since the widespread adoption of electronic information systems by enterprises — the Holy Grail has been complete, integrated access to all data. With the canonical RDF data model, that promise is now at hand.

Conversion: So Many Structs, So Little Time

Diversity is a truism of human communications as captured by the biblical Tower of Babel and the many thousands of current human languages. Diversity in data formats, serializations, notations and languages is a similar truism. We term the expression of each of these varied forms of data a struct.

While an internal canonical representation of data makes sense for the reasons noted above, pragmatic information systems must recognize the inherent diversity and chaos of data in the real world. The history of trying to find single representations or to impose standards via fiat have singularly failed. That will continue to be so due in part to inertia and legacy, sunk investments, existing infrastructure, and the purposes for the data.

In pursuing a vision of data interoperability, then, conversion is an essential glue for cementing understanding with what exists and will exist.

RDB-to-RDF

Arguably the largest source of structured data are enterprise and government information systems, with the predominant data representation being the relational data model managed by relational schema. Much of this data is also cleaner and mission critical compared to other sources in the wild. Fortunately, there are many logical and conceptual affinities between the relational model and the one for RDF [5].

Just as there are many RDFizers for simpler forms of data structs (see next), there are also nice ways to convert relational schema to RDF automatically. Given these overall conceptual and logical affinities the W3C is also in the process of graduating an incubator group to an official work group, RDB2RDF, focused on methods and specifications for mapping relational schema to RDF.

Amongst all techniques covered in this paper, Structured Dynamics views the layering of RDF ontologies over existing relational data stores as one of the most promising and important. Given the advantages of RDF for interoperability, this area should be a major emphasis of current and new vendors and service providers.

RDFizers

Much data, however, resides in much smaller datasets and often for less formal purposes than what is found in enterprise databases. Some of this data is geared for exchange or standardization; much is emerging from Web and Internet applications and uses; and much might be local or personal in nature, such as simple lists or spreadsheets.

RDF is well suited to convert (“RDFize”) these simpler and more naïve data formats. In my original census about 18 months ago, as reported in ‘Structs’: Naïve Data Formats and the ABox, I listed about 90 converters. My most recent update now lists nearly double that number, with about 150 converters [6]:

URN handlers (in addition to IRI and URI):

  • DOI
  • LSID
  • OAI

RDF

  • Serialization formats:
    • N3
    • RDF/XML
    • Turtle
  • Languages and ontologies:
    • AB Meta
    • Annotea
    • APML
    • AtomOWL
    • Bibliographic Ontology
    • Creative Commons
    • EXIF
    • FOAF
    • Java
    • Javadoc
    • MARC/MODS
    • Meta Standards
    • Music Ontology
    • Natural Language
    • Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH)
    • Open Geospatial
    • OWL
    • SIOC
    • SIOCT
    • SKOS
    • UMBEL
    • vCard
    • XML
    • Others
  • (X)HTML pages
  • Embedded Microformats and GRDDL [7]:
    • DC
    • eRDF
    • geoURL
    • Google Base
    • hAudio
    • hCalendar
  • Embedded Microformats and GRDDL (con’t):
    • hCard
    • hListing
    • hResume
    • hReview
    • HR-XML
    • Ning
    • RDFa
    • relLicense
    • SVG
    • XBRL
    • XFN
    • xFolk
    • XR-XML
    • XSLT
  • Syndication Formats:
    • Atom
    • OPML
    • OCS
    • RSS 1.1
    • RSS 2.0
    • XBEL (for bookmarks)
  • REST-style Web service APIs:
    • Amazon
    • Apple
    • Calais
    • CrunchBase
    • Del.icio.us
    • Digg
    • Discogs
    • Disqus
    • eBay
    • Facebook
    • Flickr
    • Freebase (MQL)
    • FriendFeed
    • Garmin
    • Get Satisfaction
    • Google
    • Hoover’s
    • HTTP (raw)
    • ISBN DB
    • Last.fm
    • Library Thing
    • Magnolia
  • REST-style Web service APIs (con’t):
    • Meetup
    • MusicBrainz
    • New York Times
    • New York Times Campaign Finance (NYTCF)
    • New York Times tags
    • Open Library
    • Open Social
    • Open Street
    • OpenLink (facets)
    • O’Reilly
    • Picasa
    • Radio Pop (BBC)
    • Rhapsody
    • Salesforce
    • Slideshare
    • Slidy
    • Technorati
    • They Work For You
    • Twine
    • Twitter
    • Weather
    • Wikipedia
    • World Bank
    • Yahoo! Finance
    • Yahoo! Maps
    • Yahoo! Weather
    • YouTube
    • Zemanta
  • Files (multitude of file formats and MIME types, including):

Many of the sources above come from new and emerging Web-based APIs, which are also huge sources of content growth. Also note that alternative formats to RDF (e.g., microformats) or leading serializations and encodings (e.g, XML, JSON) also have many converter options.

For many typical naïve data structs, the data is represented as attribute-value pairs, which easily lend themselves to conversion to RDF as instance records [8]. See further the Authoring section below.

Tagging: The 80% Solution

An apocryphal statistic is that 80% to 85% of all information resides in unstructured text [9]. Besides lacking recent validation, this claim from a decade ago often attributed to Merrill Lynch also precedes much of the Internet and the emergence of metadata and tagging. Nevertheless, what is true is that written text content is ubiquitous and the majority of it remains untagged or uncharacterized by any form of metadata.

While such information can be searched, it only matches when exact terms match. This means that related information, particularly in the form of conceptual relationships and inferencing, can not be applied to untagged text content.

While information extraction — the basis by which tags for entities and concepts can be obtained — has been an active topic of research for two decades, it is only recently that we have begun to see Web-scale extractors appear. Examples include Yahoo’s term extractor, Thomson Reuter’s Calais, or Google’s Squared, to name but a few.

scones - Subject Concepts or Named Entities In Structured Dynamics’ case we have been working on the scones (Subject Concepts Or Named EntitieS) extractor for quite a while. scones uses rather simple natural language processing (NLP) methods as informed by concept ontologies and named entity (instance record) dictionaries to help guide the extraction process. The co-occurrence of matches between concepts and entities also aids the disambiguation task (though additional modules may be invoked with alternative disambiguation methods). In prototype forms, the resulting tags can be managed separately or fed to user interfaces or re-injected back into the original content as RDFa.

There are literally dozens of such extractors and services presently available on the Web and many that are available as open source or commercial products. Some are mostly algorithm based using machine-learning techiques or statistics, while others are gazeteer- or dictionary-driven.

These systems will lead to rapid tagging of existing content and the removal of some of the early “chicken-and-egg” challenges associated with the semantic Web. These systems will also be combined with the many existing bookmarking and tagging services.

So, just as we will see federation and interoperability of conventional data, we will also see linkages to relevant and supporting text content accompanying it. This combination, in turn, will also lead to richer browsing and discovery experiences.

Authoring: The Neglected Third Leg of the Stool

In addition to conversion and tagging, authoring is the third leg of the stool to expose structured data. It is a neglected leg to the structured content stool, and one important to make it easier for datasets to be easily exposed as RDF linked data.

One of the reasons for the proliferation of data structs has been the interest in finding notations and conventions for easier reading and authoring of small datasets. There have literally been hundreds of various formats proposed over decades for conveying lightweight data structures. Most have been proprietary or limited to specific domains or users. Some, such as fielded text, structured text, simple declarative language (SDL), or more recently YAML or its simpler cousin JSON, have become more widely adopted and supported by formal specifications, tools or APIs. JSON, especially, is a preferred form for Web 2.0 applications.

What has been less clear or intuitive in these forms, again mostly based on an attribute-value pair orientation, is how to adequately relate them to a more capable data model, such as RDF. In JSON or YAML, for example, the notations include the concepts of objects, arrays and datatypes (among other conventions). Other structures lack even these constructs.

To take the case of JSON as might be related to RDF, there are a couple of efforts to define representation conventions from Talis and GBV for serializing RDF. There was a floated idea for an RDF version of JSON called RDFON that has now evolved into the TURF approach. JDIL (JSON data integration layer) instructs how to add namespaces to JSON to enable encoding RDF. Jim Ley, Kanzaki Masahide and Dave Beckett (likely among others) have written simple and straightforward RDF and Turtle parsers and converters for JSON. And, still further examples are Beckett’s Triplr and Sören Auer‘s ASKW Triplify lightweight conversion services involving many different formats.

Because JSON is easily readable, can drive many Web 2.0 applications and widgets, and lends itself to fast conversions and tools in various scripting languages, Structured Dynamics was commissioned by the Bibliographic Knowledge Network (BKN) to formalize a BibJSON specification suitable for BibTeX-like data records and citations with an extensible schema to be converted to RDF.

The emerging result of that BibJSON effort will be published shortly. The specification includes conventions and vocabularies for creating bibliographic and citation instance records, for specifying structural schema, and for creating linkage files between the attributes in the record files with existing and new schema. BibJSON is itself grounded in IRON, which is an instance record and object notation developed by Structured Dyamics that can be serialized as JSON (called irJSON), XML (called irXML) or comma-separated values (or CSV comma-delimited files, called commON).

The purpose of these notations and serializations is to provide easier authoring environments and scripting support to RDF-ready datasets. This approach has the advantage of shielding most users from the nuances or lengthiness of RDF (though the N3 serialization also works well).

The design and development of commON was especially geared to using spreadsheets as authoring environments that would enable easy creation of instance record tables or simple hierarchical or outline structures. For example, here is a sample portion of Sweet Tools specified in a spreadsheet using the commON notation:

Once the philosophy and role of naïve data structs is embraced — with an appreciation of the many converters now available or easily written for translating to RDF — it becomes easier to determine data forms appropriate to the tools and natural work flow of the users and tasks at hand. Under this mindset, the role of RDF is to be the eventual conversion target, but not necessarily what is used for intermediate work tasks, and in particular not for authoring.

Getting it All Organized

OK, so now all of this stuff is converted, tagged or authored. How does it relate? What is the relation of one dataset to another dataset? Is there a context or framework for laying out these conceptual roadmaps?

UMBEL (Upper Mapping and Binding Exchange Layer) Two years ago as we looked at the state of RDF and the incipient semantic Web as promised via linked data, we saw that such a specific framework was lacking. (Though there were existing higher-level ontologies, either their complexity or design were not well-suited to these purposes.) It was at that time that Frédérick Giasson and I began to formulate the UMBEL (Upper Mapping and Binding Exchange Layer) ontology, which eventually led to our more formal business partnership and Structured Dynamics.

What we sought to achieve with UMBEL was a coherent reference framework of about 20,000 subject concepts, connected and acting like constellations in the information sky for orienting content and new datasets. At the same time, we wanted to create a general vocabulary and approach that would lend themselves to creation of domain-specific ontologies, which would also naturally tie in and inter-relate to the more general UMBEL structure.

This objective was achieved, though UMBEL deserves an upgrade to OWL 2 and some other pending improvements. A number of domain ontologies have been created and now relate to UMBEL. So, rather than being an end to itself, UMBEL was one of the necessary infrastructure pieces to help make the vision herein a reality.

Similar approaches may be taken by others with new domain ontologies based on the UMBEL vocabulary with tie-in as appropriate to existing subject concepts, or by mapping to the existing UMBEL structure.

Of course, UMBEL is not an absolute condition to the vision herein. However, insofar as users desire to see multiple datasets inter-related, including the use of existing public Web data, something akin to UMBEL and related domain ontologies will be necessary to provide a similar roadmap.

Making it All Available

The parts and techniques discussed so far pertain almost exclusively to data and content. But, these structures so created now can inform data-driven applications which also now must be deployed. To do so, Structured Dynamics is committed to what is known as a Web-oriented architecture (WOA):

WOA = SOA + WWW + REST

WOA is a subset of the service-oriented architectural style, wherein discrete functions are packaged into modular and shareable elements (“services”) that are made available in a distributed and loosely coupled manner. WOA generally uses the representational state transfer (REST) architectural style defined by Roy Fielding in his 2000 doctoral thesis; Fielding is also one of the principal authors of the Hypertext Transfer Protocol (HTTP) specification.

REST provides principles for how resources are defined and used and addressed with simple interfaces without additional messaging layers such as SOAP or RPC. The principles are couched within the framework of a generalized architectural style and are not limited to the Web, though they are a foundation to it.

structWSF Web Services FrameworkWithin this design we need a suite of generic functions and tools that are driven by the structure of the available datasets. The deployment vehicle and design we have implemented to provide this WOA design is structWSF [10].

structWSF is a platform-independent Web services framework for accessing and exposing structured RDF data. Its central organizing perspective is that of the dataset. These datasets contain instance records, with the structural relationships amongst the data and their attributes and concepts defined via ontologies (schema with accompanying vocabularies). The master or controlling Web service in the framework is the module for granting access and use rights to datasets based on permissions.

The structWSF middleware framework is generally RESTful in design and is based on HTTP and Web protocols and open standards. The initial structWSF framework comes packaged with a baseline set of about a dozen Web services in CRUD, browse, search and export and import. More services can readily be added to the system.

All Web services are exposed via APIs and SPARQL endpoints. Each request to an individual Web service returns an HTTP status and a document of resultsets (if the query result is not null). Each results document can be serialized in many ways, and may be expressed as either RDF or pure XML.

In initial release, structWSF has direct interfaces to the Virtuoso RDF triple store (via ODBC, and later HTTP) and the Solr faceted, full-text search engine (via HTTP). However, structWSF has been designed to be fully platform-independent. The framework is open source (Apache 2 license) and designed for extensibility.

No End in Sight

Like all visions, there are many aspects and many improvements possible. This vision is definitely a work-in-progress with no end in sight.

But, meaningful movement embracing the full scope of this vision is doable today. Structured Dynamics welcomes inquiries regarding any of these aspects, improvements to them, or application to your specific needs and problems.

We also welcome you to come back and visit our blogs (Fred’s is found here). We try to speak on various aspects of this vision in all of our posts and are pleased to share our experience and insights as gained.


[1] Metcalfe’s law states that the value of a telecommunications network is proportional to the square of the number of users of the system (n2), where the linkages between users (nodes) exist by definition. For information bases, the data objects are the nodes. Linked data works to add the connections between the nodes. We can thus modify the original sense to become the Linked Data Law: the value of a linked data network is proportional to the square of the number of links between the data objects. I first presented this formulation about a year ago in What is Linked Data?
[2] This piece introduces for the first time a couple of efforts-in-progress by Structured Dynamics. For a general tools listing, see my own Sweet Tools listing of about 800 semantic Web and -related tools.
[3] As quoted in The Lever, “”Archimedes, however, in writing to King Hiero, whose friend and near relation he was, had stated that given the force, any given weight might be moved, and even boasted, we are told, relying on the strength of demonstration, that if there were another earth, by going into it he could remove this.” from Plutarch (c. 45-120 AD) in the Life of Marcellus, as translated by John Dryden (1631-1700).
[4] The canonical data model is especially prevalent in enterprise application integration. An interesting animated visualization of the canonical data model may be found at: http://soa-eda.blogspot.com/2008/03/canonical-data-model-visualized.html.
[5] An excellent piece on those relations was written by Andrew Newman a bit over a year ago; see Andrew Newman, 2007. “A Relational View of the Semantic Web,” published on XML.com, March 14, 2007; http://www.xml.com/pub/a/2007/03/14/a-relational-view-of-the-semantic-web.html. RDF can be modeled relationally as a single table with three columns corresponding to the subject-predicate-object triple. Conversely, a relational table can be modeled in RDF with the subject IRI derived from the primary key or a blank node; the predicate from the column identifier; and the object from the cell value. Because of these affinities, it is also possible to store RDF data models in existing relational databases. (In fact, most RDF “triple stores” are RDBM systems with a tweak, sometimes as “quad stores” where the fourth tuple is the graph.) Moreover, these affinities also mean that RDF stored in this manner can also take advantage of the historical learnings around RDBMS and SQL query optimizations.
[6] The largest source for RDFizers, which it calls Sponger cartridges, is from OpenLink Software in relation to its Virtuoso universal server. Most of its converters use XSLT stylesheets to translate to RDF, but the system has other conversion capabilities as well. Two additional OpenLink resources are a clickable diagram of converters and relationships with links and an online storehouse of available XSLT converters. In addition, two other sources — the W3C’s Semantic Web wiki with converter listings and MIT’s Simile program and listing of RDFizers — have a rich set of listings. Note that many of the categories shown on the table also have multiple sources of converters, so that the absolute number of converters has also grown faster than the unique formats supported.
[7] GRDDL (Gleaning Resource Descriptions from Dialects of Languages) is a W3C markup format for getting RDF data out of XML and XHTML documents using explicitly associated transformation algorithms, typically represented in XSLT GRDDL accomodates a wide variety of dialects (see one listing) and can be combined with arbitrary transformation mechanisms (though currently mostly based on XSLTs).
[8] We characterize instance records as representing the “ABox”, in accordance with our working definition for description logics:

“Description logics and their semantics traditionally split concepts and their relationships from the different treatment of instances and their attributes and roles, expressed as fact assertions. The concept split is known as the TBox (for terminological knowledge, the basis for T in TBox) and represents the schema or taxonomy of the domain at hand. The TBox is the structural and intensional component of conceptual relationships. The second split of instances is known as the ABox (for assertions, the basis for A in ABox) and describes the attributes of instances (and individuals), the roles between instances, and other assertions about instances regarding their class membership with the TBox concepts.”
[9] One of the more recent discussions of this percentage is by Seth Grimes, Unstructured Data and the 80 Percent Rule, 2009.
[10] structWSF is also designed to integrate with third-party apps and content management systems (CMSs) to provide the user interfaces to these functions. The first implementation of this design is conStruct SCS, a structured content system that extends the basic Drupal content management framework. conStruct enables structured data and its controlling vocabularies (ontologies) to drive applications and user interfaces.