Rogério Ferreira Rodrigues

Ginga-NCL: the declarative environment of the Brazilian digital TV system

As in all main terrestrial DTV Systems, the Brazilian middleware, named Ginga, supports both declarative applications (through its presentation, or declarative, environment Ginga-NCL) and procedural applications (through its execution, or procedural, environment Ginga-J). Since hybrid applications are common, either type of Ginga application may make use of facilities of both presentation and execution application environments. This paper focuses on the presentation environment Ginga-NCL. The main Brazilian inovations are then presented, regarding the Ginga architecture, the declarative NCL language specification, the editing commands for live application production, and the transport data structure.

Modeling, authoring and formatting hypermedia documents in the HyperProp system

Abstract. This paper discusses multimedia and hypermedia modeling, authoring and formatting tools, presenting the proposals of the HyperProp system and comparing them to related work. It also highlights several research challenges that still need to be addressed. Moreover, it stresses the importance of document logical structuring and considers the use of compositions in order to represent context relations, synchronization relations, derivation relations and task relations in hypermedia systems. It discusses temporal and spatial synchronization among multimedia objects and briefly presents the HyperProp graphical authoring and formatting tools. Integration between the proposed system and the WWW is also addressed.

Live editing of hypermedia documents

In some hypermedia system applications, like interactive digital TV applications, authoring and presentation of documents may have to be done concomitantly. This is the case of live programs, where not only some contents are not known a priori, but also some temporal and spatial relationships, among program media objects, may have to be established after the unknown content definition. This paper proposes a method for hypermedia document live editing, preserving not only the presentation semantics but also the logical structure semantics defined by an author. To validate this proposal, an implementation has been done for the Brazilian Digital TV System, which is also presented.

XConnector: extending XLink to provide multimedia synchronization

This paper proposes XConnector, a language for the creation of complex hypermedia relations with causal or constraint semantics. XConnector allows the definition of relations independently of which resources are related. Another feature is the specification of relation libraries, providing reuse in relationship definition. The main goal is to improve linking languages or the linking modules of hypermedia authoring languages in order to provide multimedia synchronization capabilities using links. Following this direction, an extension to W3C XLink is proposed, incorporating XConnector facilities.

NCL 2.0: integrating new concepts to XML modular languages

This paper presents the main new features of Nested Context Language (NCL) version 2.0. NCL 2.0 is a modular and declarative hypermedia language, whose modules can be combined to other languages, such as SMIL, to provide new facilities. Among the NCL 2.0 new features, we can highlight the support for handling hypermedia relations as first-class entities, through the definition of hypermedia connectors, and the possibility of specifying any semantics for a hypermedia composition, using the concept of composition templates. Another important goal of this paper is to describe a framework to facilitate the development of NCL parsing and processing tools. Based on this framework, the paper comments several implemented compilers, which allow, for instance, the conversion of NCL documents into SMIL specifications.

Inter and intra media-object QoS provisioning in adaptive formatters

The development of hypermedia/multimedia systems requires the implementation of an element, usually known as formatter, which is in charge of receiving the specification of a document (structure, media-object relationships and presentation descriptions) and controlling its presentation. The process of controlling and maintaining the presentation of a hyperdocument with an output of acceptable quality is a QoS orchestration problem, which needs to be treated by formatters in two related levels: the inter media-object and the intra media-object orchestration. This paper aims at discussing the issues associated to QoS provisioning in hypermedia systems, focusing on the design and implementation of formatters. We propose a QoS framework for hypermedia formatters based on a generic quality of service model for communication environments. The paper also comments the experience obtained in the framework instantiation for the HyperProp system formatter.

Versioning Support in the HyperProp System

This paper discusses version control for hypermedia models with composite nodes that allow distinct representations of the same information segment to be treated as versions. Several problems arise from the possibility of a node being contained in different nested compositions, as well as being presented (edited) with different representations. The paper discusses these issues, relating partial solutions proposed in several hypermedia models and presenting the proposal defined in the Nested Context Model of the HyperProp system.

Variable and state handling in NCL

Most time-based declarative languages have limited support for variable definition and manipulation, which causes developers to resort to imperative languages. However, a declarative language should provide a variable handling model sufficiently rich to describe a wide range of interactive applications, avoiding, as much as possible, the help of an imperative scripting language. On the other hand, the declarative simplicity should not be lost, leaving for the imperative objects more complex manipulations, with the necessary care to avoid any impact in the application’s temporal graph. Based on this principle, variables and the presentation state are handled by NCL and Ginga-NCL, as discussed in this paper. NCL is the declarative language of the Brazilian Terrestrial Digital TV System (SBTVD) supported by its middleware called Ginga. NCL and Ginga-NCL are part of ISDB standards and also of ITU-T Recommendations for IPTV services.

IMPROVING THE EXPRESSIVENESS OF XML-BASED HYPERMEDIA AUTHORING LANGUAGES

This paper presents some desirable requirements for hypermedia authoring declarative languages, discussing which ones are satisfied by existent languages, such as SMIL, and which facilities are not offered. It also presents how the missing requirements could be offered in an XML-based language, in order to improve its expressiveness, presenting elements and attributes that could be incorporated in its DTD. Among the facilities, we can highlight the possibility for reusing document components and their presentation characteristics, offering flexibility in temporal duration specifications, adapting a document presentation according to user navigation, and specifying n-ary relationships expressing causality or constraint among components.

Authoring and formatting of documents based on event-driven hypermedia models

This paper presents a critical analysis of specification and presentation environments for hypermedia documents with time constraints. The solutions implemented in the HyperProp authoring and execution environment are also presented.