Peering Browser Http with SPARQL : Al application Http RdF often beyond your ownership or control triple(and potentially hostile), requires funda RDF HTML store mentally new approaches to ensuring engine nteroperability. No longer can we expect a priori standardization of ev Figure 1. Sample fractal"architecture of Semantic Web applications. Dynami air-wise interaction between all possi content engines, backed by rDf triple stores, act as both producers and ble systems we anticipate interacting consumers of"semantic"data. Data exchange can be facilitated using, for with; indeed, we can't even anticipate example, SPARQL all future scenarios Operating in such an open-ended world requires mechanisms for limiting technologies for scientific data integra- an RDF triple store: a component that the decision-making scope. For exam- tion, particularly in the biology sector. allows, among other things, the integra- ple, when seeking a particular kind of Joost(www.joost.com),thenewInter-tionofheterogeneousdatasourcesandnewservicetouseyoullwanttolimit net TV platform that made big news in repositories. SPARQL's emergence as the the set of candidates to something thats February in announcing a partnership standard query language for RDF lets contextually relevant(such as those with Viacom, uses RDF extensively. In data stores expose themsel that are offered in your current loca- fact, Joost announced recently that it SPARQL endpoints, thus enabling flex- tion). Similarly, traditional access-con will provide its open source RDF back- ible data exchange among systems. It is trol mechanisms might not scale to end technology to the Apache Founda- leading the way toward Web applica- situations in which we have an open- tion(www.apache.org),makingittionsthatexhibitakindof"fractal"endedsetofsystemsandusersweneed much more widely available for use by structure, with patterns in which one new decision-making mechanisms to Web developers. component uses another as a data enforce more flexible policies From the It's interesting to note how little of source(via SPARQL, for example)and representational viewpoint, Semantic this effort focuses on what was once acts as a data source to yet another Web technologies offer the possibility thought to be the Semantic Web's component (see Figure 1). Such archi- of implementing these kinds of techno major business sector: the integration tectures open up new possibilities for logical frameworks and platforms. We of enterprise data assets via ontologies. the original vision of Web services and claim that context-awareness and poli It isnt that such work isn't going on- loosely coupled distributed systems. cy-awareness are complementary rather Oracle, IBM, and several startups are Essentially, we can view Semantic than separate mechanisms - think of all providing important capabilities in Web technology as a novel approach to policies (and their enforcement )as a that area- but embedding RDF and interoperability: application developers particular kind of context. OWL on the Web, via the all-important can defer to the runtime accessible In the longer term, given that URI mechanism, is a key part of the semantics of a dialogue between two Semantic Web technologies are matur emerging excitement over Semantic information systems even after the sys- ing as a means of describing things, we Web technologies. Whereas the re- tems have been deployed By using rea- could use their representational power search community is widely exploiting soning mechanisms to access implied to describe things in the real world. One the al technologies that motivate, in information within conversations of view is that the physical objects will particular, the OWL DL sublanguage, the explicit statements, and by enabling become Web-accessible in that we will languages' more"Webby"features- systems to dynamically add capabilities be able to represent them via metadata sometimes referred to as the "dark by acquiring new ontologies and data to Just like applying semantic technolo side"of the Semantic Web+-are pow- reason over, the Semantic Web lets us gies to problems of interoperability in ering the Web 3.0 technology space. build future-proof systems that have a ubiquitous computing environments, chance of" doing the right thing"even describing physical things will expand Beyond Web 3.0 in unexpected situations. This approach our scope beyond the current Web. This How do we see the future of the Seman- is particularly ble to os is not unlike when some argue that Web tic Web and, most importantly, the and situations in which interoperability services merely exploit mechanisms and application of Semantic Web technolo- is critical - for example, the ubiquitous technologies developed for the Web, but gies for"mainstream"IT problems and computing vision of environments with really have nothing to do with it. systems? With Web 3.0, these technolo- pervasive embedded computation. To Semantic Web efforts provide an ap- gies are finding fertile ground in multi- connect, say, your handheld device to a proach to constructing flexible, intelli- tiered Web applications in which the dynamically changing set of dozens, if gent information systems; some are middle tier can be implemented using not hundreds, of other systems that are Web-based applications, but we're cer www.computer.org/internet/ IEEEINTERNET COMPUTING92 www.computer.org/internet/ IEEE INTERNET COMPUTING Peering technologies for scientific data integra￾tion, particularly in the biology sector. Joost (www.joost.com), the new Inter￾net TV platform that made big news in February in announcing a partnership with Viacom, uses RDF extensively. In fact, Joost announced recently that it will provide its open source RDF back￾end technology to the Apache Founda￾tion (www.apache.org), making it much more widely available for use by Web developers. It’s interesting to note how little of this effort focuses on what was once thought to be the Semantic Web’s major business sector: the integration of enterprise data assets via ontologies. It isn’t that such work isn't going on — Oracle, IBM, and several startups are all providing important capabilities in that area — but embedding RDF and OWL on the Web, via the all-important URI mechanism, is a key part of the emerging excitement over Semantic Web technologies. Whereas the re￾search community is widely exploiting the AI technologies that motivate, in particular, the OWL DL sublanguage, the languages’ more “Webby” features — sometimes referred to as the “dark side” of the Semantic Web4 — are pow￾ering the Web 3.0 technology space. Beyond Web 3.0 How do we see the future of the Seman￾tic Web and, most importantly, the application of Semantic Web technolo￾gies for “mainstream” IT problems and systems? With Web 3.0, these technolo￾gies are finding fertile ground in multi￾tiered Web applications in which the middle tier can be implemented using an RDF triple store: a component that allows, among other things, the integra￾tion of heterogeneous data sources and repositories. SPARQL’s emergence as the standard query language for RDF lets many data stores expose themselves as SPARQL endpoints, thus enabling flex￾ible data exchange among systems. It is leading the way toward Web applica￾tions that exhibit a kind of “fractal” structure, with patterns in which one component uses another as a data source (via SPARQL, for example) and acts as a data source to yet another component (see Figure 1). Such archi￾tectures open up new possibilities for the original vision of Web services and loosely coupled distributed systems. Essentially, we can view Semantic Web technology as a novel approach to interoperability: application developers can defer to the runtime accessible semantics of a dialogue between two information systems even after the sys￾tems have been deployed. By using rea￾soning mechanisms to access implied information within conversations of explicit statements, and by enabling systems to dynamically add capabilities by acquiring new ontologies and data to reason over, the Semantic Web lets us build future-proof systems that have a chance of “doing the right thing” even in unexpected situations. This approach is particularly amenable to scenarios and situations in which interoperability is critical — for example, the ubiquitous computing vision of environments with pervasive embedded computation. To connect, say, your handheld device to a dynamically changing set of dozens, if not hundreds, of other systems that are often beyond your ownership or control (and potentially hostile), requires funda￾mentally new approaches to ensuring interoperability. No longer can we expect a priori standardization of every pair-wise interaction between all possi￾ble systems we anticipate interacting with; indeed, we can’t even anticipate all future scenarios. Operating in such an open-ended world requires mechanisms for limiting the decision-making scope. For exam￾ple, when seeking a particular kind of new service to use, you’ll want to limit the set of candidates to something that’s contextually relevant (such as those that are offered in your current loca￾tion). Similarly, traditional access-con￾trol mechanisms might not scale to situations in which we have an open￾ended set of systems and users: we need new decision-making mechanisms to enforce more flexible policies. From the representational viewpoint, Semantic Web technologies offer the possibility of implementing these kinds of techno￾logical frameworks and platforms. We claim that context-awareness and poli￾cy-awareness are complementary rather than separate mechanisms — think of policies (and their enforcement) as a particular kind of context. In the longer term, given that Semantic Web technologies are matur￾ing as a means of describing things, we could use their representational power to describe things in the real world. One view is that the physical objects will become Web-accessible in that we will be able to represent them via metadata. Just like applying semantic technolo￾gies to problems of interoperability in ubiquitous computing environments, describing physical things will expand our scope beyond the current Web. This is not unlike when some argue that Web services merely exploit mechanisms and technologies developed for the Web, but really have nothing to do with it. Semantic Web efforts provide an ap￾proach to constructing flexible, intelli￾gent information systems; some are Web-based applications, but we’re cer￾Figure 1. Sample “fractal” architecture of Semantic Web applications. Dynamic content engines, backed by RDF triple stores, act as both producers and consumers of “semantic” data. Data exchange can be facilitated using, for example, SPARQL. RDF triple store HTTP HTTP with SPARQL HTML Browser RDF Dynamic content engine RDF triple store AI application Code and reasoner Ontology Address: > go @ Internet Zone Back Forward Stop Refresh Print Home Mail Dynamic content engine