Tuesday, May 29, 2007

imho Ocean Semantic…..


Semantic interoperability is a non-issue when everybody adopts the same vocabulary, frame of reference, and expectations from the get-go, and when there’s no question who governs the domain in which these shared understandings apply. Interoperability only becomes an issue when autonomous semantic domains must interact for their mutual benefit. In those cases, all parties must agree on a mapping or translation between their respective vocabularies. In such circumstances, how do semantic domains square, coordinate, mediate, and reconcile their domain-specific ontologies with ontologies in other domains, or with foundation ontologies that apply more horizontally?

Governance among autonomous domains--that’s the essence of federation, as I’ve discussed previously in this blog on several occasions over the past 30 months. To dust off and slightly extend my prior definition of federation (last rehashed in the “Arch of Governance” thread a year ago): Federation is a governance structure in which autonomous domains choose to honor each other’s decisions and accept each other’s assertions in some realm of human endeavor—such as identity management, semantics/data management, or SOA management--subject to business contracts, trust relationships, interoperability agreements, and local policies.

One thought that occurred to me is that semantic federation can be modeled along the same general lines as identity federation. Within any federated interaction (semantic, identity, etc.), at least one party “asserts” some statement about some entity, and at least one party “relies” upon that assertion when making one or more decisions. Where semantic federation is concerned, we’re not talking SAML “assertion” messages or anything of the sort.

Rather, we’re construing an ontology (expressed in OWL, RDF, or any other knowledge representation language) as asserting that a particular controlled vocabulary applies in some domain (e.g,. your organization, your application, your system, etc.). And we’re interpreting ontology-compliant data structures (expressed in XSD or other schema standards) as assertions/statements about specific entities/classes/relationships/etc within a domain. And we “rely” on these semantic assertions (ontologies and data) when we choose to discover, access, retrieve, and import them from the asserting/source domain, and then reformat, match, map, translate, merge, aggregate, store, and otherwise use them in our target domain.

Of course, that semantic-bridging process is how cross-system interoperability has been conducted since the dawn of distributed computing. Integrators have always ascertained the meaning of source data in its original application, process, or system context, while also considering the meaning, schema, and format of equivalent data elements in target systems, and then defining the mappings necessary to ensure that the meaning/context of the data is preserved when being translated between the source and target systems.

In a federated semantic environment, interoperability needn’t require reciprocal handshakes (i.e., business contracts, trust relationships, interoperability agreements, etc.) among interacting parties. In fact, interoperability can be and often is a one-way flow of metadata from source to target systems. All that’s necessary is that at least one party—usually, the source/asserting party--make its full meaning and expectations completely transparent and unambiguous to the others, and that the others (the relying parties) agree to accept that meaning and live up to those expectations. At least one party must control the vocabulary, and all parties—asserting and relying--must consistently adhere to that vocabulary.

If governance over that federated lingua franca is shared, that’s all well and good, but not absolutely essential, for understandings to be mutual. In fact, it’s best that most of the foundation and domain-specific ontologies are controlled/decreed by various “higher authorities” (e.g., standards bodies, industry associations, etc.), so that most common vocabularies are as transparent and unambiguous as possible. And to the limited extent that the interacting parties choose to “handshake” the definitions of the remaining vocabulary elements through common ontology repositories, or through an agreed-upon data stewardship/governance administrative workflow, the common understanding is nailed down solid.

Semantic stewardship. That’s the process under which organizations—internally and externally—work out the policies regarding which ontologies (i.e., vocabularies, glossaries, metadata, definitions, etc.) will be asserted, in which formats/schemas, and which will be relied upon, per which ontology-controlling authorities, under which governance roles and workflows, and with which mappings and translations, under which requirements, use cases, and circumstances.

Federated semantic stewardship. The decision to accept, map, and adapt some other domain’s vocabulary to your circumstances. Because it fits.

More to come.


Wednesday, May 16, 2007

imho Ocean Semantic....


Semantic interoperability requires shared understanding by all parties of the full context, content, and consequences of their actions within a given application domain.

The focus of the W3C's Semantic Web initiative has been on shared understanding as crystallized and governed by domain-specific "ontologies." An ontology is a grammar and vocabulary for representing entities and relationships, constraints and containments, applications and manifestations within a domain. RDF, with its subject-predicate-object "triples," is one such grammar, and OWL expands RDF's expressive power for making meaningful, machine-readable, URI/XML-based statements about any entity and any relationship in any domain that chooses to represent itself online.

But ontologies can't be shared unless two or more parties choose to agree on them, or if they are mandated by whoever controls the domains within which two or more parties agree to interact. And they can't serve as a stable, broadly understood and accepted common denominator unless they are under governance by some recognized authority within the domain they purport to support. Which leads to some key questions, where semantic inteoperability is concerned. What is a semantic domains? What authorities control the domains? From what sources do these domain authorities, controllers, governors, or stewards derive their authority? What procedures do they use to define, disseminate, administer, and revise ontologies for their domains? How do they square, coordinate, reconcile, and federate their domain-specific ontologies with ontologies in other related domains, or with foundation ontologies that apply more horizontally?

Semantic domains are springing up all over, often as B2B data-standardization initiatives within particular industries. Look at the RDF and OWL specs for a glimpse at domain authorities in the birthing. Under RDF spec, section 6, "Some RDF Applications: RDF in the Field," note the intiatives and their scope/applicability/institutional backing: "Dublin Core Metadata Initiative" (ECM vendors, digital library operators, electronic publishers), "Publishing Requirements for Industry Standard Metadata (magazine publishers), "RDF Site Summary" (online content syndicators and aggregators), "Common Information Model" (electric power research institute), "Gene Ontology Consortium" (biomedical researchers), and "Describing Device Capabilities and User Preferences" (mobile device, infrastructure, carrier). And that document's a couple of years old...there are many fresher examples of horizontal, vertical, regional, B2B, intra-corporate, and other ontology-making bodies and initiatives.

Of course, an ontology is only one component in a "domain model," which should also define the governance, roles, workflows, data matching/cleansing, exception-handling, and master-data-management rules, and other policies and best practices that prevail in that (real or virtual) (B2B or intra-corporate) slice of the universe. Taken all together, the domain model is the practical/institutional context within which all participants adopt a common, controlled vocabulary (i.e., ontology) to catalyze shared understandings.

Notice the word "federation," earlier in this post, in the same sentence as the word "ontologies." Shared understandings are hard to catalyze when the world is fragmented into fiefdoms. But that's the world we will always live in....the SemanticWeb governance structure is and will remain indelibly federated.

More to come.


Tuesday, May 15, 2007

imho Ocean Semantic...


Scoping for my upcoming BCR article on Semantic Web, per the proposal I just floated last night to Eric and Sandy:

· Semantic Web is an industry initiative to expand end-to-end, standards-based semantic interoperability throughout SOA environments.

· The concept of a Semantic Web takes the notion of the World Wide Web (WWW) a step further:

o Essentially, the WWW treats the Internet as an open book that—through common interoperability standards such as DNS, IP, HTTP, HTML, and XML—makes content everywhere readable, searchable, and comprehensible to human consumers.

o The Semantic Web extends that concept to non-human consumers, so that the meaning, context, structure, operations, reference, use, goal state, implied processing, relationships, scope, and purpose of any entity, especially content, can—through XML-based interoperability standards such as RDF and OWL--be everywhere unambiguously readable, searchable, comprehensible, and actionable to services, applications, bots, and machines, and also, via that machine-mediated abstract virtualization layer, to human beings.

· In theory, the concept of the Semantic Web can be interpreted either very broadly or very narrowly:

o God’s eye view: as a supermagical identification, metadata, description, representation, and policy layer that enables universal, automatic, comprehensive end-to-end interoperability across every macro or micro entity on every imaginable level.

o Worm’s eye view: as standardized XML-based schemas that define how content can be tagged with self-describing metadata in accordance with controlled, domain-specific, agreed-upon semantic vocabularies known as “ontologies.”

· In practice, Semantic Web techniques can potentially be applied in the following areas:

o Enterprise content management (ECM): enable more powerful/flexible content discovery, indexing, search, classification, cataloging, aggregation, correlation, navigation, mapping, transformation, and management across federated domains

o Enterprise service bus (ESB): enable speedier, automatic, policy-driven, multilayered application, process, and service interoperability across federated domains

o Enterprise information integration (EII): support virtualized, composite, unified viewing, query, and update of disparate data that has been retrieved from heterogeneous sources across federated domains

· So far, there is considerable academic discussion of Semantic Web concepts, and standards definition at the W3C, but surprisingly little commercial implementation of such Semantic Web specifications as RDF and OWL in the ECM, ESB, and EII markets.

However, there is a growing emphasis on and implementation of heterogeneous semantic interoperability—considered broadly—in all of these markets. To some extent, the so-called Semantic Web standards and initiative are only one piece of a much larger puzzle that is coming together in a environment that should more properly be called “Semantic SOA.”

So you can sort of see where I'm going with "federation" re "ontologies." But I still need to flesh that out.

More to come.