This post was originally published in the Talis “Nodalities” blog and in “Nodalities” magazine issue 5.
he Linked Data web might usefully be viewed as an incremental evolution beyond Web 2.0. Instead of disconnected silos of data accessible only through disconnected custom APIs, we have datasets that are deeply connected to one another using simple web links, allowing applications to “follow their nose” to find additional relevant data about a specific resource. Custom protocols and data formats are the realm of the early web; the future of the web is in an increased emphasis on standards like HTTP, URIs and RDF that ironically have been in use for many years.
Describing this as a “back to basics” approach wouldn’t be far wrong. Many might dispute that RDF is far from simple, but this overlooks the elegance of its core model. Working within the constraints of standard technologies and the web architecture allows for a greater focus on the real drivers behind data publishing: what information do we want to share, and how is it modelled?
Answering those questions should be relatively easy for any organisation. All businesses have useful datasets that their customers and business partners might usefully access; and they have the domain expertise required to structure that data for online reuse. And, should any organisation want some additional creative input, the Linked Data community has also put together a shopping list  to highlight some specific datasets of interest. This list is worth reviewing alongside the Linked Data graph , to explore both the current state of the Linked Data web and the directions in which it is potentially going to grow.
Beyond the first questions of what and how to share data, there are other issues that need to be considered. These range from internal issues that organisations face in attempting to justify the sharing of data online, through to larger concerns that may impact the Linked Data ecosystem. For the purposes of this of article, this ecosystem can be divided up into two main categories: data publishers, who publish and share information online; and data consumers, who make use of these rich datasets.
There is obvious overlap between these two categories: many organisations will fall into both camps, as do we all through our personal contributions to the web. However, for this paper I want to focus primarily on business and organisational participants, and attempt to illustrate the different issues that are relevant to these roles.
Data Publishers Perspective
The first issue facing any organisation is how to justify both the initial and ongoing effort required to support the publishing of Linked Data. Depending on existing infrastructure this may range from a relatively small effort to a major engineering task—particularly true if content has to be converted from other formats or new workflows introduced. In “A Call to Arms” in the last issue of Nodalities , John Sheridan and Jeni Tennison provided some insight into how to address the technology hurdle by using technologies like RDFa.
But can this effort be made sustainable? Can the initial investment and ongoing costs be recouped? And, if a dataset becomes popular and grows to become very heavily used, can the infrastructure supporting the data publishing scale to match?
The general aim with enabling access to data is that it will foster network effects, and drive increasing traffic and usage towards existing products and services. There are success stories aplenty (Amazon, Ebay, Salesforce, etc) that illustrate that there is real and not imagined potential.
But this justification overlooks some important distinctions. Firstly for some organisations, e.g. charities and non-governmental organisations information dissemination is part of their mission and there may not be other chargeable services to which additional traffic may be driven. In this scenario everything must be sustainable from the outset. Secondly, it also overlooks the fact that the data being shared may itself be an asset that can be commoditised. The value of access to raw data, stripped of any bundling application, has never been clearer, or been easier to achieve. New business models are likely to arise around direct access to quality data sources. Simple usage-based models are already prevalent on a number of Web 2.0 services and APIs—the free basic access fosters network effects, while the tiered pricing provides more reliable revenue for the data publisher.
Software as a service and cloud computing models undoubtedly have a role to play in addressing the sustainability and scaling issue, allowing data publishers to build out a publishing infrastructure that will support these operations without significant capital investments. But few of the existing services are really firmly targeted at this particular niche: while computing power and storage are increasingly readily available, support for Linked Data publishing or metered access to resources are not yet common-place.
This is where Talis and the Talis Platform have a distinct offering: by supporting organisations in their initial exploration of Linked Data publishing, with a minimum of initial investment, and a scaleable, standards based infrastructure, it becomes much easier to justify dipping a toe into the “Blue Ocean” (see Nodalities issue 2 ).
Data Consumers Perspective
Let’s turn now to another aspect of the Linked Data ecosystem, and consider the data consumers perspective.
One issue that quickly becomes apparent when integrating an application with a web service or Linked Dataset is the need to move beyond simple “on the fly” data requests, e.g. to compose (“mash-up”) and view data sources in the browser, towards polling and harvesting increasingly large chunks of a Linked Dataset.
What drives this requirement? In part it is a natural consequence and benefit of the close linking of resources: links can be mined to find additional relevant metadata that can be used to enrich an application. The way that the data is exposed, e.g. as inter-related resources, is unlikely to always match the needs of the application developer who must harvest the data in order to index, process and analyse it so that it best fits the use cases of her application.
Creating an efficient web-crawling infrastructure is not an easy task, particularly as the growth of the Linked Data web continues and the pool of available data grows. Technologies like SPARQL do go some way towards mitigating these issues, as a query language allows for more flexibility in extracting data. However provision of a stable SPARQL endpoint may be beyond the reach of smaller data publishers, particularly those who are adopting the RDFa approach of instrumenting existing applications with embedded data. SPARQL also doesn’t help address the need to analyse datasets, e.g. to mine the graph in order to generate recommendations, analyse social networks, etc.
Just as few applications carry out large scale crawling of the web, instead relying on services from a small number of large search engines, it seems reasonable to assume that the Linked Data web will similarly organise around some “true” semantic web search engines that provide data harvesting and acquisition services to machines rather than human users. Issues of trust will also need to be addressed within this community as the Linked Data web matures and becomes an increasing target for spam and other malicious uses. Inaccuracies and inconsistencies are already showing up.
The Talis Platform aims to address these issues by ultimately providing application developers with ready access to Linked Datasets, avoiding the need for individual users and organisations to repeatedly crawl the web. Value-added services can then be offered across these data sources, allowing features, such as graph analysis (e.g. recommendations), to become commodity services available to all. The intention is not to try and mirror or aggregate the whole Linked Data web, this would be unfeasible, but rather collate those datasets that are of most value and use to the community, as well as shepherding the publishing of new datasets by working closely with data publishers.
As an intermediary, the Talis Platform can also address another issue: that of scaling service infrastructure to meet the requirements of data consumers without requiring data publishers to do likewise. It seems likely that data publishers may ultimately choose to “multi-home” their datasets, e.g. publishing directly onto the Linked Data web and also within environments such as the Talis Platform in order to allow consumers more choice in the method of data access.
The bootstrapping phase of the Linked Data web is now behind us. As a community, we need to begin considering the next steps, especially as the available data continues to grow. This article has attempted to illustrate a few from a wide range of different issues that we face. While technology development, particularly around key standards like SPARQL, rules and inferencing, and the creation of core vocabularies, will always underpin the growth of the semantic web, increasingly it will be issues such as serviceable infrastructure and sustainable business models that will come to the fore.
At Talis we are thinking carefully about the role we might play in addressing those issues and playing our part in enabling the Linked Data ecosystem to flourish.