Kingsley Idehen's Blog Data Space

In recent times a lot of the commentary and focus re. Virtuoso has centered on the RDF Quad Store and Linked Data. What sometimes gets overlooked is the sophisticated Virtual Database Engine that provides the foundation for all of Virtuoso's data integration capabilities.

In this post I provide a brief re-introduction to this essential aspect of Virtuoso.

What is it?

This component of Virtuoso is known as the Virtual Database Engine (VDBMS). It provides transparent high-performance and secure access to disparate data sources that are external to Virtuoso. It enables federated access and integration of data hosted by any ODBC- or JDBC-accessible RDBMS, RDF Store, XML database, or Document (Free Text)-oriented Content Management System. In addition, it facilitates integration with Web Services (SOAP-based SOA RPCs or REST-fully accessible Web Resources).

Why is it important?

In the most basic sense, you shouldn't need to upgrade your existing database engine version simply because your current DBMS and Data Access Driver combo isn't compatible with ODBC-compliant desktop tools such as Microsoft Access, Crystal Reports, BusinessObjects, Impromptu, or other of ODBC, JDBC, ADO.NET, or OLE DB-compliant applications. Simply place Virtuoso in front of your so-called "legacy database," and let it deliver the compliance levels sought by these tools

In addition, it's important to note that today's enterprise, through application evolution, company mergers, or acquisitions, is often faced with disparately-structured data residing in any number of line-of-business-oriented data silos. Compounding the problem is the exponential growth of user-generated data via new social media-oriented collaboration tools and platforms. For companies to cost-effectively harness the opportunities accorded by the increasing intersection between line-of-business applications and social media, virtualization of data silos must be achieved, and this virtualization must be delivered in a manner that doesn't prohibitively compromise performance or completely undermine security at either the enterprise or personal level. Again, this is what you get by simply installing Virtuoso.

How do I use it?

The VDBMS may be used in a variety of ways, depending on the data access and integration task at hand. Examples include:

Relational Database Federation

You can make a single ODBC, JDBC, ADO.NET, OLE DB, or XMLA connection to multiple ODBC- or JDBC-accessible RDBMS data sources, concurrently, with the ability to perform intelligent distributed joins against externally-hosted database tables. For instance, you can join internal human resources data against internal sales and external stock market data, even when the HR team uses Oracle, the Sales team uses Informix, and the Stock Market figures come from Ingres!

Conceptual Level Data Access using the RDF Model

You can construct RDF Model-based Conceptual Views atop Relational Data Sources. This is about generating HTTP-based Entity-Attribute-Value (E-A-V) graphs using data culled "on the fly" from native or external data sources (Relational Tables/Views, XML-based Web Services, or User Defined Types).

You can also derive RDF Model-based Conceptual Views from Web Resource transformations "on the fly" -- the Virtuoso Sponger (RDFizing middleware component) enables you to generate RDF Model Linked Data via a RESTful Web Service or within the process pipeline of the SPARQL query engine (i.e., you simply use the URL of a Web Resource in the FROM clause of a SPARQL query).

It's important to note that Views take the form of HTTP links that serve as both Data Source Names and Data Source Addresses. This enables you to query and explore relationships across entities (i.e., People, Places, and other Real World Things) via HTTP clients (e.g., Web Browsers) or directly via SPARQL Query Language constructs transmitted over HTTP.

Conceptual Level Data Access using ADO.NET Entity Frameworks

As an alternative to RDF, Virtuoso can expose ADO.NET Entity Frameworks-based Conceptual Views over Relational Data Sources. It achieves this by generating Entity Relationship graphs via its native ADO.NET Provider, exposing all externally attached ODBC- and JDBC-accessible data sources. In addition, the ADO.NET Provider supports direct access to Virtuoso's native RDF database engine, eliminating the need for resource intensive Entity Frameworks model transformations.

Related

• Attaching ODBC or JDBC accessible Relational Tables to Virtuoso
• Using an HTML based Wizard to Generate RDF based Linked Views over Relational Tables
• Screencast Demonstrating Wizard based generation of RDF based Linked Data Views Part 1
• Screencast Demonstrating Wizard based generation of RDF based Linked Data Views Part 1
• Generating RDF based Linked Data from non RDF based Web Resources via the Sponger
• Building ADO.NET based Entity Frameworks Views over Relational Data
• Building Silverlight Rich Internat Applicaitons using ADO.NET, Entity Frameworks, and RDF based Linked Data.

I am pleased to announce the immediate availability of the Virtuoso ADO.NET 3.5 data provider for Microsoft's .NET platform.

What is it?

A data access driver/provider that provides conceptual entity oriented access to RDBMS data managed by Virtuoso. Naturally, it also uses Virtuoso's in-built virtual / federated database layer to provide access to ODBC and JDBC accessible RDBMS engines such as: Oracle (7.x to latest), SQL Server (4.2 to latest), Sybase, IBM Informix (5.x to latest), IBM DB2, Ingres (6.x to latest), Progress (7.x to OpenEdge), MySQL, PostgreSQL, Firebird, and others using our ODBC or JDBC bridge drivers.

Benefits?

Technical:

It delivers an Entity-Attribute-Value + Classes & Relationships model over disparate data sources that are materialized as .NET Entity Framework Objects, which are then consumable via ADO.NET Data Object Services, LINQ for Entities, and other ADO.NET data consumers.

The provider is fully integrated into Visual Studio 2008 and delivers the same "ease of use" offered by Microsoft's own SQL Server provider, but across Virtuoso, Oracle, Sybase, DB2, Informix, Ingres, Progress (OpenEdge), MySQL, PostgreSQL, Firebird, and others. The same benefits also apply uniformly to Entity Frameworks compatibility.

Bearing in mind that Virtuoso is a multi-model (hybrid) data manager, this also implies that you can use .NET Entity Frameworks against all data managed by Virtuoso. Remember, Virtuoso's SQL channel is a conduit to Virtuoso's core; thus, RDF (courtesy of SPASQL as already implemented re. Jena/Sesame/Redland providers), XML, and other data forms stored in Virtuoso also become accessible via .NET's Entity Frameworks.

Strategic:

You can choose which entity oriented data access model works best for you: RDF Linked Data & SPARQL or .NET Entity Frameworks & Entity SQL. Either way, Virtuoso delivers a commercial grade, high-performance, secure, and scalable solution.

How do I use it?

• Using Visual Studio 2008 & Virtuoso to build an Entity Frameworks based Windows forms application
• Using Visual Studio 2008 & Virtuoso to build an ADO.NET Data Services based application

Note: When working with external or 3rd party databases, simply use the Virtuoso Conductor to link the external data source into Virtuoso. Once linked, the remote tables will simply be treated as though they are native Virtuoso tables leaving the virtual database engine to handle the rest. This is similar to the role the Microsoft JET engine played in the early days of ODBC, so if you've ever linked an ODBC data source into Microsoft Access, you are ready to do the same using Virtuoso.

Related

• Entity Oriented Data Access
• Yoda & the Data FORCE.

I just stumbled across an post from ITBusines Edge titled: How Semantic Technology Can Help Companies with Integration. While reading the post I encountered the term: Master Data Manager (MDM), and wondered to myself, "what's that?" only to realize it's the very same thing I described as a Data Virtualization or Virtual Database technology (circa. 1998).

Now, if re-labeling can confuse me when applied to a realm I've been intimately involved with for eons (internet time). I don't want to imagine what it does for others who aren't that intimately involved with the important data access and data integration realms.

On the more refreshing side, the article does shed some light on the potency of RDF and OWL when applied to the construction of conceptual views of heterogeneous data sources.

"How do you know that data coming from one place calculates net revenue the same way that data coming from another place does? You’ve got people using the same term for different things and different terms for the same things. How do you reconcile all of that? That’s really what semantic integration is about."

BTW - I discovered this article via another titled: Understanding Integration And How It Can Help with SOA, that covers SOA and Integration matters. Again, in this piece I feel the gradual realization of the virtues that RDF, OWL, and RDF Linked Data bring to bear in the vital realm of data integration across heterogeneous data silos.

Conclusion

A number of events, at the micro and macro economic levels, are forcing attention back to the issue of productive use of existing IT resources. The trouble with the aforementioned quest is that it ultimately unveils the global IT affliction known as: heterogeneous data silos, and the challenges of pain alleviation, that have been ignored forever or approached inadequately as clearly shown by the rapid build up of SOA horror stories in the data integration realm.

Data Integration via conceptualization of heterogenous data sources, that result in concrete conceptual layer data access and management, remains the greatest and most potent application of technologies associated with the "Semantic Web" and/or "Linked Data" monikers.

Related

• InforWorld 2003 Innovator article
• 2006 Podcast Interview with Jon Udell
• Enterprise Information Integration
• One of several posts about our Virtuoso Universal Server and Conceptual Model based data integration
• History of Virtuoso
• Mike Bergman's post titled: WOA: A New Enterprise Partner for Linked Data

After reading Bengee's interview with CrunchBase, I decided to knock up a quick interview remix as part of my usual attempt to add to the developing discourse.

CrunchBase: When we released the CrunchBase API, you were one of the first developers to step up and quickly released a CrunchBase Sponger Cartridge. Can you explain what a CrunchBase Sponger Cartridge is?

Me: A Sponger Cartridge is a data access driver for Web Resources that plugs into our Virtuoso Universal Server (DBMS and Linked Data Web Server combo amongst other things). It uses the internal structure of a resource and/or a web service associated with a resource, to materialize an RDF based Linked Data graph that essentially describes the resource via its properties (Attributes & Relationships).

CrunchBase: And what inspired you to create it?

Me: Bengee built a new space with your data, and we've built a space on the fly from your data which still resides in your domain. Either solution extols the virtues of Linked Data i.e. the ability to explore relationships across data items with high degrees of serendipity (also colloquially known as: following-your-nose pattern in Semantic Web circles).

Bengee posted a notice to the Linking Open Data Community's public mailing list announcing his effort. Bearing in mind the fact that we've been using middleware to mesh the realms of Web 2.0 and the Linked Data Web for a while, it was a no-brainer to knock something up based on the conceptual similarities between Wikicompany and CrunchBase. In a sense, a quadrant of orthogonality is what immediately came to mind re. Wikicompany, CrunchBase, Bengee's RDFization efforts, and ours.

Bengee created an RDF based Linked Data warehouse based on the data exposed by your API, which is exposed via the Semantic CrunchBase data space. In our case we've taken the "RDFization on the fly" approach which produces a transient Linked Data View of the CrunchBase data exposed by your APIs. Our approach is in line with our world view: all resources on the Web are data sources, and the Linked Data Web is about incorporating HTTP into the naming scheme of these data sources so that the conventional URL based hyperlinking mechanism can be used to access a structured description of a resource, which is then transmitted using a range negotiable representation formats. In addition, based on the fact that we house and publish a lot of Linked Data on the Web (e.g. DBpedia, PingTheSemanticWeb, and others), we've also automatically meshed Crunchbase data with related data in DBpedia and Wikicompany data.

CrunchBase: Do you know of any apps that are using CrunchBase Cartridge to enhance their functionality?

Me: Yes, the OpenLink Data Explorer which provides CrunchBase site visitors with the option to explore the Linked Data in the CrunchBase data space. It also allows them to "Mesh" (rather than "Mash") CrunchBase data with other Linked Data sources on the Web without writing a single line of code.

CrunchBase: You have been immersed in the Semantic Web movement for a while now. How did you first get interested in the Semantic Web?

Me: We saw the Semantic Web as a vehicle for standardizing conceptual views of heterogeneous data sources via context lenses (URIs). In 1998 as part of our strategy to expand our business beyond the development and deployment of ODBC, JDBC, and OLE-DB data providers, we decided to build a Virtual Database Engine (see: Virtuoso History), and in doing so we sought a standards based mechanism for the conceptual output of the data virtualization effort. As of the time of the seminal unveiling of the Semantic Web in 1998 we were clear about two things, in relation to the effects of the Web and Internet data management infrastructure inflections: 1) Existing DBMS technology had reached it limits 2) Web Servers would ultimately hit their functional limits. These fundamental realities compelled us to develop Virtuoso with an eye to leveraging the Semantic Web as a vehicle from completing its technical roadmap.

CrunchBase: Can you put into layman’s terms exactly what RDF and SPARQL are and why they are important? Do they only matter for developers or will they extend past developers at some point and be used by website visitors as well?

Me: RDF (Resource Description Framework) is a Graph based Data Model that facilitates resource description using the Subject, Predicate, and Object principle. Associated with the core data model, as part of the overall framework, are a number of markup languages for expressing your descriptions (just as you express presentation markup semantics in HTML or document structure semantics in XML) that include: RDFa (simple extension of HTML markup for embedding descriptions of things in a page), N3 (a human friendly markup for describing resources), RDF/XML (a machine friendly markup for describing resources).

SPARQL is the query language associated with the RDF Data Model, just as SQL is a query language associated with the Relational Database Model. Thus, when you have RDF based structured and linked data on the Web, you can query against Web using SPARQL just as you would against an Oracle/SQL Server/DB2/Informix/Ingres/MySQL/etc.. DBMS using SQL. That's it in a nutshell.

CrunchBase: On your website you wrote that “RDF and SPARQL as productivity boosters in everyday web development”. Can you elaborate on why you believe that to be true?

Me: I think the ability to discern a formal description of anything via its discrete properties is of immense value re. productivity, especially when the capability in question results in a graph of Linked Data that isn't confined to a specific host operating system, database engine, application or service, programming language, or development framework. RDF Linked Data is about infrastructure for the true materialization of the "Information at Your Fingertips" vision of yore. Even though it's taken the emergence of RDF Linked Data to make the aforementioned vision tractable, the comprehension of the vision's intrinsic value have been clear for a very long time. Most organizations and/or individuals are quite familiar with the adage: Knowledge is Power, well there isn't any knowledge without accessible Information, and there isn't any accessible Information without accessible Data. The Web has always be grounded in accessibility to data (albeit via compound container documents called Web Pages).

Bottom line, RDF based Linked Data is about Open Data access by reference using URIs (HTTP based Entity IDs / Data Object IDs / Data Source Names), and as I said earlier, the intrinsic value is pretty obvious bearing in mind the costs associated with integrating disparate and heterogeneous data sources -- across intranets, extranets, and the Internet.

CrunchBase: In his definition of Web 3.0, Nova Spivack proposes that the Semantic Web, or Semantic Web technologies, will be force behind much of the innovation that will occur during Web 3.0. Do you agree with Nova Spivack? What role, if any, do you feel the Semantic Web will play in Web 3.0?

Me: I agree with Nova. But I see Web 3.0 as a phase within the Semantic Web innovation continuum. Web 3.0 exists because Web 2.0 exists. Both of these Web versions express usage and technology focus patterns. Web 2.0 is about the use of Open Source technologies to fashion Web Services that are ultimately used to drive proprietary Software as Service (SaaS) style solutions. Web 3.0 is about the use of "Smart Data Access" to fashion a new generation of Linked Data aware Web Services and solutions that exploit the federated nature of the Web to maximum effect; proprietary branding will simply be conveyed via quality of data (cleanliness, context fidelity, and comprehension of privacy) exposed by URIs.

Here are some examples of the CrunchBase Linked Data Space, as projected via our CruncBase Sponger Cartridge:

1. Amazon.com
2. Microsoft
3. Google
4. Apple

My podcast interview with Paul Miller of Talis is out. As I listened to the podcast (naturally awkward affair) I got a first hand sense of Paul's mastery of the art of interviewing, even when dealing with a fast talking data blitzers like me. Personally, I think I still talk a little too fast (the Nigerian in me), especially when the subject matter hones right into the epicenter of my professional passions: Open Data Access and Heterogeneous Data Integration (aka. Virtual Database Technology) -- so you may need to rewind every now and then during the interview :-)

During this particular podcast interview, I deliberately wanted to have an conversation about the practical value of Linked Data, rather than the technical innards. The fundamental utility of Linked Data remains somewhat mercurial, and I am certainly hoping to do my bit at the upcoming Linked Data Planet conference re. demonstrating and articulating linked data value across the blurring realms of "the individual" and "the enterprise".

Note to my old schoolmates on Facebook: when you listen to this podcast you will at least reconcile "Uyi Idehen" with "Kingsley Idehen". Unfortunately, Facebook refuses to let me Identify myself in the manner I choose. Ideally, I would like to have the name: "Kingsley (Uyi) Idehen" associated with my Facebook ID since this is the Identifier known to my personal network of friends, family, and old schoolmates. This Identity predicament is a long running Identity case study in the making.

Wordpress is a Weblog platform comprised of the following:

1. User Interface - PHP
2. Application Logic - PHP
3. Data Storage (SQL RDBMS) - MySQL via PHP-MySQL
4. Application Server - Apache

In the form above (the norm), Wordpress data can be injected into the Linked Data Web via RDFization middleware such as theVirtuoso Sponger (built into all Virtuoso instances) and Triplr. The downside of this approach is that the blog owner doesn't necessary possess full control over their contributions to the emerging Giant Global Graph or Linked Data.

Another route to Linked Data exposure is via Virtuoso's Metaschema Language for producing RDF Views over ODBC/JDBC accessible Data Sources, that enables the following setup:

1. User Interface - PHP
2. Application Logic - PHP
3. Data Storage (SQL RDBMS) - MySQL via the PHP-MySQL data access interface
4. Virtual Database linkage of MySQL Tables into Virtuoso
5. RDF View generated over the Virtual SQL Tables
6. Application Server - Virtuoso which provides Linked Data Deployment such that RDF Linked Data is exposed when requested by Web User Agents.

Alternatively, you can also exploit Virtuoso as the SQL DBMS, RDF DBMS, Application Server, and Linked Data Deployment platform:

1. User Interface - PHP
2. Application Logic - PHP
3. Data Storage (SQL RDBMS) - Virtuoso via PHP-ODBC data access interface (* ODBC is Virtuoso's native SQL CLI/API *)
4. RDF View generated over the Native SQL Tables
5. Application Server - Virtuoso which provides Linked Data Deployment such that RDF Linked Data is exposed when requested by Web User Agents (e.g. OpenLink RDF Browser, Zitgist Data Viewer, DISCO Hyperdata Browser, and Tabulator).

Benefits?

• Each user account gets a proper Linked Data URI (ID) that can me meshed/smushed with other IDs (so you add data from this new blog space to other linked data sources associated with you other URIs/IDs)
• Each post gets a proper URI All data is now query-able via SPARQL Discoverability increases exponentially (without drop in relevance in either direction i.e. discovering or being discovered)

How Do I map the WordPress SQL Schema to RDF using Virtuoso?

• Determine the RDF Schema or Ontologies that define the Classes for which you will be producing instance data (e.g. SIOC and FOAF)
• Declare URI/IRI generator functions (*special Virtuoso functions*)
• Use SPARQL Graph patterns to apply URI/IRI generator functions to Tables, Views, Table Values mode Stored Procedures, Query Resultsets as part of RDBMS to RDF mapping

Read the Meta Schema Language guide or simply apply our "WordPress SQL Schema to RDF" script to your Virtuoso hosted instance. Of course, there are other mappings that cover other PHP applications deployed via Virtuoso:

• phpBB3 SQL Schema to RDF
• Drupal SQL Schema to RDF
• MediaWiki SQL Schema to RDF

Live Demos?

• Virtuoso Hosting phpBB3 (example User URI)
• Virtuoso Hosting Drupal (example User URI)
• Virtuoso Hosting MediaWiki (example User URI)

John Schmidt, from Informatica, penned an interesting post titled: IT Doesn't Matter - Integration Does.

Yes, integration is hard, but I do profoundly believe that what's been happening on the Web over the last 10 or so years also applies to the Enterprise, and by this I absolutely do not mean "Enterprise 2.0" since "2.0" and productive agility do not compute in my realm of discourse.

large collections of RSS feeds, Wikiwords, Shared Bookmarks, Discussion Forums etc.. when disconnected at the data level (i.e. hosted in pages with no access to the "data behind") simply offer information deluge and inertia (there are only so many hours for processing opaque information sources in a given day).

Enterprises fundamentally need to process information efficiently as part of a perpetual assessment of their relative competitive Strengths, Weaknesses, Opportunities, and Threats (SWOT), in existing and/or future markets. Historically, IT acquisitions have run counter intuitively to the aforementioned quest for "Ability" due to the predominance of "rip and replace" approach technology acquisition that repeatedly creates and perpetuates information silos across Application, Database, Operating System, Development Environment boundaries. The sequence of events typically occurs as follows:

1. applications are acquired on a problem by problem basis
2. back-end application databases are discovered once ad-hoc information views are sought by information workers
3. back-end database disparity across applications is discovered once holistic views are sought by knowledge workers (typically domain experts).

In the early to mid 90's (pre ubiquitous Web), operating system, programming language, operating system, and development framework independence inside the enterprise was technically achievable via ODBC (due to it's platform independence). That said, DBMS specific ODBC channels alone couldn't address the holistic requirements associated with Conceptual Views of disparate data sources, hence the need for Data Access Virtualization via Virtual Database Engine technology.

Just as is the case on the Web today, with the emergence of the "Linked Data" meme, enterprises now have a powerful mechanism for exploiting the Data Integration benefits associated with generating Data Objects from disparate data sources, endowed with HTTP based IDs (URIs).

Conceptualizing access to data exposed Databases APIs, SOA based Web Services (SOAP style Web Services), Web 2.0 APIs (REST style Web Services), XML Views of SQL Data (SQLX), pure XML etc.. is problem area addressed by RDF aware middleware (RDFizers e.g Virtuoso Sponger).

Here are examples of what SQL Rows exposed as RDF Data Objects (identified using HTTP based URIs) would look like outside or behind a corporate firewall:

Customer - Alfreds Futterkiste

Customer Contact - Maria Anders

Salesrep - Nancy Davolio

Customer Orders Numbers - 11084, 11011, 11078, 11085

What's Good for the Web Goose (Personal Data Space URIs) is good for the Enterprise Gander (Enterprise Data Space URIs).

Related

Data Access - A Cultural or Technical Challenge?

Note: An updated version of a previously unpublished blog post:

Continuing from our recent Podcast conversation, Jon Udell sheds further insight into the essence of our conversation via a “Strategic Developer” column article titled: Accessing the web of databases.

Below, I present an initial dump of a DataSpace FAQ below that hopefully sheds light on the DataSpace vision espoused during my podcast conversation with Jon.

What is a DataSpace?

A moniker for Web-accessible atomic containers that manage and expose Data, Information, Services, Processes, and Knowledge.

What would you typically find in a Data Space? Examples include:

• Raw Data - SQL, HTML, XML (raw), XHTML, RDF etc.
  
  
• Information (Data In Context) - XHTML (various microformats), Blog Posts (in RSS, Atom, RSS-RDF formats), Subscription Lists (OPML, OCS, etc), Social Networks (FOAF, XFN etc.), and many other forms of applied XML.

• Web Services (Application/Service Logic) - REST or SOAP based invocation of application logic for context sensitive and controlled data access and manipulation.

• Persisted Knowledge - Information in actionable context that is also available in transient or persistent forms expressed using a Graph Data Model. A modern knowledgebase would more than likely have RDF as its Data Language, RDFS as its Schema Language, and OWL as its Domain  Definition (Ontology) Language. Actual Domain, Schema, and Instance Data would be serialized using formats such as RDF-XML, N3, Turtle etc).

How do Data Spaces and Databases differ?
Data Spaces are fundamentally problem-domain-specific database applications. They offer functionality that you would instinctively expect of a database (e.g. AICD data management) with the additonal benefit of being data model and query language agnostic. Data Spaces are for the most part DBMS Engine and Data Access Middleware hybrids in the sense that ownership and control of data is inherently loosely-coupled.

How do Data Spaces and Content Management Systems differ?
Data Spaces are inherently more flexible, they support multiple data models and data representation formats. Content management systems do not possess the same degree of data model and data representation dexterity.

How do Data Spaces and Knowledgebases differ?
A Data Space cannot dictate the perception of its content. For instance, what I may consider as knowledge relative to my Data Space may not be the case to a remote client that interacts with it from a distance, Thus, defining my Data Space as Knowledgebase, purely, introduces constraints that reduce its broader effectiveness to third party clients (applications, services, users etc..). A Knowledgebase is based on a Graph Data Model resulting in significant impedance for clients that are built around alternative models. To reiterate, Data Spaces support multiple data models.

What Architectural Components make up a Data Space?

• ORDBMS Engine - for Data Modeling agility (via complex purpose specific data types and data access methods), Data Atomicity, Data Concurrency, Transaction Isolation, and Durability (aka ACID).
  
  
• Virtual Database Engine - for creating a single view of, and access point to, heterogeneous SQL, XML, Free Text, and other data. This is all about Virtualization at the Data Access Level.

• Web Services Platform - enabling controlled access and manipulation (via application, service, or protocol logic) of Virtualized or Disparate Data. This layer handles the decoupling of functionality from monolithic wholes for function specific invocation via Web Services using either the SOAP or REST approach.

Where can I see a DataSpace along the lines described, in action?

Just look at my blog, and take the journey as follows:

• Front Door (Web 1.0)
• Lounge (Web 2.0) via GData or OpenSearch
• Floor Plan via FOAF or SIOC RDF Data Sets (Graphs)
• Rest of the house (beyond Web 2.0) sending  SPARQL Queries to a SPARQL Endpoint.
  

What about other Data Spaces?

There are several and I will attempt to categorize along the lines of query method available:
Type 1 (Free Text Search over HTTP):
Google, MSN, Yahoo!, Amazon, eBay, and most Web 2.0 plays .

Type 2 (Free Text Search and XQuery/XPath over HTTP)
A few blogs and Wikis (Jon Udell's and a few others)

•    SIOC enabled sites (aka points of semantic web presence)
  
•    PingTheSemantic
  

• My Blog Data Space (as stated earlier in this post)
  
• My General Data Space - (ditto; note that this is currently experimental)
  

What About Data Space aware tools?

•    OpenLink Ajax Toolkit - provides Javascript Control level binding to Query Services such as XMLA for SQL, GData for Free Text, OpenSearch for Free Text, SPARQL for RDF, in addition to service specific Web Services (Web 2.0 hosted solutions that expose service specific APIs)
•    Semantic Radar - a Firefox Extension
•    PingTheSemantic - the Semantic Webs equivalent of Web 2.0's weblogs.com
•    PiggyBank - a Firefox Extension

I am pleased to unveil (officially) the fact that Virtuoso is now available in Open Source form.

What Is Virtuoso?

A powerful next generation server product that implements otherwise distinct server functionality within a single server product. Think of Virtuoso as the server software analog of a dual core processor where each core represents a traditional server functionality realm.

Where did it come from?

The Virtuoso History page tells the whole story.

What Functionality Does It Provide?

1. Object-Relational DBMS Engine (ORDBMS like PostgreSQL and DBMS engine like MySQL)

2. XML Data Management (with support for XQuery, XPath, XSLT, and XML Schema)

3. RDF Triple Store (or Database) that supports SPARQL (Query Language, Transport Protocol, and XML Results Serialization format)

4. Service Oriented Architecture (it combines a BPEL Engine with an ESB)

5. Web Application Server (supports HTTP/WebDAV)

6. NNTP compliant Discussion Server

90% of the aforementioned functionality has been available in Virtuoso since 2000 with the RDF Triple Store being the only 2006 item.

What Platforms are Supported

The Virtuoso build scripts have been successfully tested on Mac OS X (Universal Binary Target), Linux, FreeBSD, and Solaris (AIX, HP-UX, and True64 UNIX will follow soon). A Windows Visual Studio project file is also in the works (ETA some time this week).

Why Open Source?

Simple, there is no value in a product of this magnitude remaining the "best kept secret". That status works well for our competitors, but absolutely works against the legions of new generation developers, systems integrators, and knowledge workers that need to be aware of what is actually achievable today with the right server architecture.

What Open Source License is it under?

GPL version 2.

What's the business model?

Dual licensing.

The Open Source version of Virtuoso includes all of the functionality listed above. While the Virtual Database (distributed heterogeneous join engine) and Replication Engine (across heterogeneous data sources) functionality will only be available in the commercial version.

Where is the Project Hosted?

On SourceForge.

Is there a product Blog?

Of course!

Up until this point, the Virtuoso Product Blog has been a covert live demonstration of some aspects of Virtuoso (Content Management). My Personal Blog and the Virtuoso Product Blog are actual Virtuoso instances, and have been so since I started blogging in 2003.

Is There a product Wiki?

Sure! The Virtuoso Product Wiki is also an instance of Virtuoso demonstrating another aspect of the Content Management prowess of Virtuoso.

What About Online Documentation?

Yep! Virtuoso Online Documentation is hosted via yet another Virtuoso instance. This particular instance also attempts to demonstrate Free Text search combined with the ability to repurpose well formed content in a myriad of forms (Atom, RSS, RDF, OPML, and OCS).

What about Tutorials and Demos?

The Virtuoso Online Tutorial Site has operated as a live demonstration and tutorial portal for a numbers of years. During the same timeframe (circa. 2001) we also assembled a few Screencast style demos (their look feel certainly show their age; updates are in the works).

BTW - We have also updated the Virtuoso FAQ and also released a number of missing Virtuoso White Papers (amongst many long overdue action items).