Traditional bookmark systems provide inadequate support for Web users with variety of devices including smart phones and their browsers. In addition, they offer very little support for sharing the bookmarks and topics between groups of users working together. Annotea annotations provide a means for users to share communication about Web documents by attaching external annotation metadata to the documents. Users can easily find annotations related to a document by using clients that present these annotations in the document context. Similarly, bookmarks can be thought of as kind of annotations that attach bookmark metadata to documents and help users find documents and informal categories or topics assigned to them. Our Annotea metadata storage and retrieval platform built on Semantic Web technologies now also supports bookmark metadata server. Clients may share, query and present the bookmarks and topics. Use of RDF metadata for bookmarks offers flexibility in connecting to other bookmark systems and to annotation functionality. The metadata is machine readable and can be converted from and to other bookmark formats. Metadata from several bookmark sources - either local or from selected bookmark servers - is trivial to merge by virtue of the underlying RDF-based data representation. It is also possible to add additional application- or user-dependent RDF properties such as links to formal ontologies to bookmarks and topics. Applications designed according to the principles of RDF will be able to accommodate this additional data even if the application can not present or edit these novel properties. The Annotea framework would also support objects that have a dual role as both bookmarks and annotations. In addition, other metadata based formats, such as RSS newsfeeds, could be presented as sources of Annotea shared bookmarks.
Bookmark data should be useful and available in many other ways. Rendering the bookmark with traditional annotation like icons on the page when the user so prefers would help the user recall context and reduce duplicated work. Shared bookmark data containing classification information would benefit users who are collaborating in similar research areas. They could open a bookmark shown on a page to find other related topics and follow them for bookmarks to other related documents.
Annotea [
Shared bookmarks use the same Annotea framework to create and maintain cooperative community indices grouping Web documents into informal categories or "topics". Annotea bookmarks are metadata about Web documents or other resources and share a similar structure with annotations. A bookmark can be catalogued under one or more topics and these topics can be presented to the user as topic hierarchies or more complex graphs. Bookmarks and topics are unambiguously identified with a URI, making it easy for users to share both the categories and the documents placed in the categories. An Annotea client could declare bookmarks to also be annotations and then present bookmarks as icons on a Web document when the document is browsed. This would help a user know immediately if she already has bookmarked a document in a certain category.
Use of metadata and URIs makes it easy to share and merge bookmarks coming from different sources. Bookmark databases with somewhat different RDF properties are still readily mergeable. A variety of presentations of the RDF data is possible. Use of this metadata design makes it easy to share bookmarks with other users, share bookmarks between browsers, and query the bookmark data in new ways not supported by current bookmark systems. Through additional properties in the data instances it is also possible to associate bookmark categories (topics) with more formal ontologies. In the following sections, we will describe in more detail the Annotea architecture for shared bookmarks, the bookmark schemas and examine some future directions for further developing Annotea.
ANNOTEA ARCHITECTURE FOR BOOKMARKS The shared bookmark application uses the same Annotea architecture as is used for annotations (see Figure 1). The annotation and bookmark metadata is stored separately from the Web documents themselves. The Hypertext Transfer Protocol is used to access this metadata from one or more RDF metadata servers. Metadata may also be stored in RDF form in local files. A user can create bookmarks and associate them with Web documents by using the functions in the client provided user interface. The same user or another user can then later use the bookmarks user interface to help find the bookmarked Web documents again or find other related information. Client implementations are free to present bookmarks in any way the developer chooses. Figure 1 also illustrates possible ways in which the user may examine the bookmarks in a topic hierarchy or as icons in the document context in a similar way as annotations are currently presented in our Amaya client.
Each individual bookmark is represented as an RDF
resource of type Bookmark. The metaphor of folders for
arranging bookmarks under informal categories or topics
has been generalized to resources of type Topic. Properties
of Topics as well as of Bookmarks are expressed as RDF
statements and stored in local files or in one or more
bookmark servers via HTTP [
SCHEMA FOR SHARED BOOKMARKS
The Annotea bookmark schema [
XBEL data can be easily mapped into the Annotea bookmark schema, though the reverse (Annotea RDF bookmark data to XBEL) will frequently involve loss of information. The shortcut resource type is intended to be used in scenarios where a user wishes to import data and add properties without exporting the added properties. Our current implementation does not yet expose an interface to shortcut resources.
The use of RDF in Annotea permits shared bookmarks to
express additional semantics either from other bookmark,
topic or annotation schemas or other not directly related
schemas. For example, a bookmark can include other
properties from the Dublin Core element set [
We briefly describe below the most common properties use
to describe an Annotea bookmark. Annotea uses the
RDF/XML namespace facility to declare and merge
properties from multiple namespaces. The classes and
properties described in this document use the following
conventions for the namespace references:
•
•
•
•
a: annotation namespace [
The document that the user has bookmarked is identified with the b:recalls property. The role of b:recalls is to identify the primary document to which the bookmark refers. The dc:title property is used to assign a title to the bookmark. The dc:description property may be used to give a longer textual description for the bookmark. To facilitate sharing of bookmark data, the dc:creator property is used to name the author who created the bookmark. The a:created and dc:date properties represent the creation and last modification time, respectively. The b:hasTopic property associates the bookmark instance with an instance of a topic. Topics are described below. We chose to model the the 'hasTopic' relationship as being a relationship between a bookmark instance and a topic rather than between the document that was bookmarked (identified with b:recalls) and a topic. This model is more flexible, as it allows a user to use a bookmark for any purpose without forcing the user to declare a property of the document itself.
Topic Resources
A topic defines an informal category for the purpose of classifying bookmarks. Topics may have subtopics and may sometimes also refer to categories in more formal ontologies. In a similar way as bookmarks, each instance of a topic is identified with a unique URIref. Figure 3 presents an instance of a topic hierarchy associating parts of an anatomy. The b:subTopicOf property defines the hierarchy. While the example in Figure 3 shows a strict hierarchy, the use of b:subTopicOf is not restricted to trees; full graphs are permitted. To keep the figure simple, most other core topic properties are not shown as these are similar to Figure 2. The dc:title property assigns a title to the topic and the dc:description property is used to give a longer textual description for the topic. The a:created and dc:date properties also have the same meaning as for bookmarks.
Shortcut Resources When sharing bookmarks, a user may wish to associate a bookmark with a personal classification scheme without declaring that the shared bookmark itself is really in this personal topic. The same user may wish to include Topics from a formal classification structure in a personal topic hierarchy where it may be inappropriate to declare that the formal topic has a b:subTopicOf relationship to the user's personal hierarchy. In such cases the user may define a "shortcut" to a bookmark or a topic. A shortcut is an indirect reference to another object.
Figure 4 shows an instance of a shortcut. A shortcut has its own b:hasTopic or b:subTopicOf properties depending on whether it is making a shortcut to a bookmark or a topic. The indirect reference is made with a b:leadsTo property. The client follows the b:leadsTo property to access the corresponding bookmark or topic as necessary.
USING BOOKMARKS IN AMAYA Client implementations are free to present bookmarks in any way the developer chooses. Currently, Amaya has implemented the basic bookmark and topic related functions. We also have separately implemented and tested the bookmark HTTP protocol with a bookmark server but need to put the user interface and the shortcut resources together with it.
The user creates a bookmark by selecting the New Bookmark item in the menu. This opens a bookmark window similar to the screen capture shown on the right in Figure 5. The user may choose to use default values for the bookmark or use the selection widgets in the window to choose one or more topics in the Topic Hierarchy field to classify the bookmark and write a title and description for it. The user can create a new topic for the hierarchy by using the New Topic button, at the bottom of the window or select New Topic from the menu.
The View Bookmarks menu item opens a hierarchy
window presenting bookmarks in a topic hierarchy. Figure
5 shows a hierarchy window on the left side with the
bookmark and topic hierarchy that is fully defined in [
An RDF model of bookmark and topics makes it easy to
present other information in the bookmark format. This
allows the user to select bookmarks when the bookmark
user interface helps her be more effective. For instance, it is
easy to define transformations from other bookmark
formats, such as the XBEL format. In addition, it is also
possible to declare semantic relationships for formats not
originally designed for bookmark use that then permit tools
to interpret other data, such as RSS [
Many groups of users working closely together want to
define their own annotation or bookmark subtypes to
convey more specialized semantics. After creating
annotations and bookmarks we expect that users will find it
useful to be able to merge them and create hybrids with
functionality from both. With new RDF metadata
definitions it is straightforward to create new annotation or
bookmark types and also define new RDF properties for
these types. Currently in Amaya these modifications are
done by updating a list of schemas that Amaya reads at
startup. In the future, we would like to enhance this and
make the definition of new annotation and bookmark types
more dynamic, and to dynamically build parts of the user
interface from the schemas without need for user interface
programming every time a new property is added. Some
preliminary investigations have been made into a stylesheet
language in cooperation with IsaViz GSS [
There are also needs for easily changing the styles of
annotations and bookmark presentations. Arakne [
RELATED WORK
URIs are designed to be created according to whatever
structure the administrator of the Web server finds most
appropriate for the particular site. In general, users are not
expected to have to recite or remember URIs. As a
consequence, bookmark systems in common browsers such
as Internet Explorer, Netscape, and Opera provide
functionality to store the URI with some information that
helps users identify it, such as descriptive title and
information about its container or folder.Often browsers or
separate converter tools [
We have some experience with transformations of
annotations. For instance, the IBM SemTag [
There is a growing body of annotation and Semantic Web
related work [
Often users don't only want to share bookmarks but also good topic hierarchies. For instance, students may sometimes benefit from copying a topic hierarchy commonly used in the research field or a group of researchers may want to start gathering research information in a commonly agreed hierarchy and then later adapt to a custom hierarchy to classify their Web documents. With Annotea it is easy to copy only skeletons of topic hierarchies when needed.
Annotea-like metadata based annotations and bookmarks
can be used not only in browsers but also with other
metadata as part of other clients or environments. For
instance, Haystack adopted RDF metadata based
annotations for searching different personal information
objects by using the natural language content of the
annotations [
CONCLUSIONS Shared bookmarks is another annotation-like application using Annotea architecture. Shared bookmarks is a tool that permits users to informally classify Web resources and share these classifications. Adding bookmark data to Annotea metadata store ensures that the basic Annotea architecture is flexible and extensible and has possibilities to support many similar kinds of applications either directly or by using some transformation rules. The biggest work ahead is to find ways to support the user interface of new annotation or bookmark types so that new annotation and bookmark types can be easily created and presented in various ways without a need to write client code to present them.
ACKNOWLEDGEMENTS:
Annotea is result of team work. Jose Kahan has
enormously influenced the current Annotea design and also
implemented the current Amaya interface for annotations
and bookmarks. Annotea also has many valuable
contributors and collaborators both within W3C and
outside and we highly appreciate the work of this
community. Some of them are mentioned in Annotea
contributors page [
Development of Annotea is supported in part by funding from US Defense Advanced Research Projects Agency (DARPA) and Air Force Research Laboratory, Air Force Materiel Command, USAF, under agreement number F30602-00-2-0593, "Semantic Web Development", by the European Commission Information Society Technologies (IST-7) programme under SWAD-Europe, and by Elisa Communications Oyj (Finland). namespace namespace namespace file Language