Many Web-based data sources and services are available as feeds, a model that provides consumers with a loosely coupled way of interacting with providers. The current feed model is limited in its capabilities, however. Though it is simple to implement and scales well, it cannot be transferred to a wider range of application scenarios. This paper conceptualizes feeds as a way to serialize query results, describes the current hardcoded query semantics of such a perspective, and surveys the ways in which extensions of this hardcoded model have been proposed or implemented. Our generalized view of feeds as query result serializations has implications for the applicability of feeds as a generic Web service for any collection that is providing access to individual information items. As one interesting and compelling class of applications, we describe a simple way in which a query-based approach to feeds can be used to support location-based services.

Location-awareness, in the form of location information about clients and location-based services provided by servers, is becoming increasingly important for networked communications in general, and wireless and mobile devices in particular. The current fragmented landscape of location concepts and location-awareness, however, is not suitable for handling location information on a Web scale. Providing users with mechanisms which allow them to control how they want to expose their location information, and thus allow control over how to share location information with others and services, is a crucial step for better location management for mobile devices. This paper presents a concept for representing location vocabularies, matching and mapping them, how these vocabularies can be used to support better privacy for users of location-based services, and better location sharing between users and services. The concept is based on a language for describing place name vocabularies, which we call "Place Markup Language (PlaceML)", and on various ways how these vocabularies can be used in a location-aware infrastructure of networked devices.

Integrating resources into the Web is an important aspect of making them accessible as part of this global information system. The integration of physical things into the Web so far has not been done on a large scale, which makes it harder to realize network effects that could emerge by the combination of today's Web content, and the integration of physical things into the Web. This paper presents a path towards a Web where physical objects are made available through RESTful principles. By using this architectural style for pervasive and ubiquitous computing scenarios, they will scale better, integrate better with other applications, and pave the path towards a "Web of Things" that seamlessly integrates conceptual and physical resources.

Location concepts are still not part of today's Web architecture, which means that applications must rely on higher-level specifications to use and provide location-oriented services. This problem can be approached in two different approaches, the first being a tightly coupled approach for scenarios targeting an integrated system architecture, and the second being a loosely coupled approach, being centered around cooperating services in the open world of the Web. This paper argues that the current specifications for location-oriented services cater mainly for the tightly coupled approach, whereas the loosely coupled approach is not yet addressed by available specifications. A more lightweight and loosely coupled approach to location-oriented services is the central issue for making the valuable data in geographic information systems better available on the Web. Only if location-oriented services can be used easily and cooperatively, today's rapidly evolving infrastructure of wireless data services and mobile devices can take full advantage of these services.

Feeds have become an important information channel on the Web, but the management of feed metadata so far has received little attention. It is hard for feed publishers to manage and publish their feed information in a unified format, and for feed consumers to manage and use their feed subscription data across various feed readers, and to share it with other users. We present a system for managing feed metadata using feeds, which we call "feed feeds". Because these feeds are Atom feeds, the widely deployed Atom and AtomPub standards can be used to manage feed metadata, making feed management available through an established API.

While the information contained in XML documents can be accessed using numerous standards and technologies, accessing the information in an XML Schema currently is only possible using proprietary technologies. XML is increasingly being used as a typed data format, and therefore it becomes more important to gain access to the type system of an XML document class, which in many cases is an XML Schema. The XML Schema Path Language (SPath) presented in this paper provides access to XML Schema components by extending the well-known XPath language to also include the domain of XML Schemas. Using SPath, XML developers gain better access to XML Schemas and thus can more easily develop software which is type- or schema-aware, and thus more robust.

The currently established formats for how a Web site can publish metadata about a site's pages, the robots.txt file and sitemaps, focus on how to provide information to crawlers about where to not go and where to go on a site. This is sufficient as input for crawlers, but does not allow Web sites to publish richer metadata about their site's structure, such as the navigational structure. This paper looks at the availability of Web site metadata on today's Web in terms of available information resources and quantitative aspects of their contents. Such an analysis of the available Web site metadata not only makes it easier to understand what data is available today; it also serves as the foundation for investigating what kind of information retrieval processes could be driven by that data, and what additional data could be provided by Web sites if they had richer data formats to publish metadata.

Annotation of multimedia resources supports a wide range of applications, ranging from associating metadata with multimedia resources or parts of these resources, to the collaborative use of multimedia resources through the act of distributed authoring and annotation of resources. Most annotation frameworks, however, are based on a closed approach, where the annotations data is limited to the annotation framework, and cannot readily be reused in other application scenarios. We present a declarative approach to multimedia annotations, which represents the annotations in an XML format independent from the multimedia resources. Using this declarative approach, multimedia annotations can be used in an easier and more flexible way, enabling application scenarios such as third-party annotations and annotation aggregation and filtering.

RESTful services on the Web expose information through retrievable resource representations that represent self-describing descriptions of resources, and through the way how these resources are interlinked through the hyperlinks that can be found in those representations. This basic design of RESTful services means that for extracting the most useful information from a service, it is necessary to understand a service's representations, which means both the semantics in terms of describing a resource, and also its semantics in terms of describing its linkage with other resources. Based on the Resource Linking Language (ReLL), this paper describes a framework for how RESTful services can be described, and how these descriptions can then be used to harvest information from these services. Building on this framework, a layered model of RESTful service semantics allows to represent a service's information in RDF/OWL. Because REST is based on the linkage between resources, the same model can be used for aggregating and interlinking multiple services for extracting RDF data from sets of RESTful services.

An increasing number of data sources and services are made available on the Web, and in many cases these information sources are or easily could be made available as feeds. However, the more data sources and services are exposed through feed-based services, the more it becomes necessary to manage and be able to share those services, so that users and uses of those services can build on the foundation of an open and decentralized architecture. In this paper we present the Feed Subscription Management (FSM) architecture, which is a model for managing feed subscriptions and supports structured feed subscriptions. Based on FSM, it is easy to build services that manage feed-based services so that those feed-based services can easily create, change and delete feed subscriptions, and that it is easily possible to share feed subscriptions across users and/or devices. Our main reason for focusing on feeds is that we see feeds as a good foundation for an ecosystem of RESTful services, and thus our architectural approach revolves around the idea of modeling services as interactions with feeds.