Annotation-based Web content Transcoding Masahiro Hori, Goh Kondoh, Kouichi Ono, Shin-ichi Hirose, and Sandeep Singhal IBM Tokyo Research Laboratory

Outline Introduction Annotation Framework Annotation-Based Transcoding System Page Fragmentation Discussion

Introduction Content adaptation is crucial for transparent Web access under different conditions. Such content adaptation also called transcoding. Results in better presentation and faster delivery to the client device. The role of annotations is to provide hints that enable a transcoding engine to make better decisions on transcoding. Existing Web documents are associated with content adaptation hints as separate annotation files.

Introduction(Cont.) Transcoding system with particular focus on the authoring- time integration between a WYSIWYG annotation tool and a transcoding module. Finally, after giving an example of content adaptation using a page fragmentation module for small-screen devices,

Annotation Framework The role of annotation is to characterize ways of content adaptation rather than to describe individual contents. The framework needs to specify a vocabulary for constraining the possibilities for decomposition, combination,and partial replacement of contents. The Resource Description Framework(RDF) is used as the syntax of annotation files. The RDF data model defines a simple model for describing relations among resources in terms of named properties and values.

Figure 1: Adaptation of HTML documents for personal computing devices

Figure 2: Framework of external annotation

Annotation Framework(Cont.) An annotation file refers to portions of an annotated document. Example: /HTML/BODY/P[3] points to the third P element of the BODY element of the annotated document. Annotation Vocabulary for Transcoding ： The vocabulary includes three types of annotation ： alternatives, splitting hints and selection criteria.

Annotation Framework(Cont.) Alternatives For example, a color image may have a grayscale image as an alternative for clients with monochrome displays. A transcoding proxy selects the one alternative that best suits the capabilities of the requested client device. Splitting hints An HTML file may be divided into multiple pages on clients with smaller display screens.The tag specifies a set of elements to be considered as a logical unit. Another usage is to provide appropriate page break points.

Annotation Framework(Cont.) Selection criteria –Client device capability –Resource requirements –Role of an annotated element –Importance of an annotated element The role tag is provided with a value attribute,which may be either proper content,advertisement,decoration or icon.

Annotation Framework(Cont.) tag specifies the priority of an annotated element. The importance value ranging from -1 (low) to 1(high). An element may not be sent to a lightweight client, when the element is provided with a decoration role and a low importance value such as –0.2.

Annotation-Based Transcoding System Transcoding Architecture Computational entities stay along the Web transaction path are called intermediaries. The intermediary-based approach allow us to provide a transcoding module as an intermediary without modifying browser or server.

Annotation-Based Transcoding System WBI ： a programmable proxy server for HTTP requests and responses. The processing is controlled by plugins available at an intermediary processor.WBI’s plugin is constructed from three fundamantal blocks ： Monitors,Editors and Generators. It realized a page-splitting module as a WBI plugin that adapts a requested document to the capabilities of a particular client.

Figure 4: Annotation-based transcoding by a page-splitting plugin

Annotation-Based Transcoding System Authoring-Time Transcoding –Annotation description may be too complicated for a simple source tag editor to maintain. –It developed an annotation tool for the external annotation by extending an existing HTML authoring tool. –It consists of a WYSIWYG editor, a source editor and a previewer.

Figure 5: Annotation tool configuration for authoring-time transcoding

Annotation-Based Transcoding System –When a previewer is invoked, a transcoding proxy is called over HTTP and the corresponding annotation is applied to the subject document. –The annotation tool is fully integrated with the transcoding proxy, users can see the results of content adaptation and revise annotation on the fly.

Page Fragmentation

Table[1] Table[2] Table[3] Search form Side bar Menu omitted

Page Fragmentation Figure 9 illustrate how the news page will be fragmented in a small display. According to the header role of the top table, the same header appears in the previewer as in the original page. The “Side bar ” anchor in the center is created in accordance with the auxiliary role.

Figure 9: Annotation for fragmentation of an actual news page

Discussion The purpose is to distinguish content with meta information. The external annotation approach allows such application- specific meta-information to be specified separately from the HTML spec.