This paper discusses the concept of universal accessibility [1, 2] to the grid within
the context of selected application domains involving social interaction such as
e-hospital, collaborative engineering, enterprise, e-government, and the media. Based
on this discussion the paper proposes a metagrid infrastructure [3] as an approach to
provide universal accessibility to the grid.
Universal accessibility is rooted in the concept of Design for All in Human Computer
Interaction[1, 2]. It aims at efficiently and effectively addressing the numerous and
diverse accessibility problems in human interaction with software applications and
telematic services. So far, the key concept of universal accessibility has been
supported by various development methodologies and platforms [4, 5]. Various
application domains benefited from research and development in this area, including
among others interactive television and media [6, 7]. Porting the concept of
universal accessibility to the grid is faced by major obstacles attributed to the
following: (a) the lack of an underlying functionality similar to that of a desktop
operating system allowing the plug and play of resources and the direct user
interaction with these resources; (b) the dilemma between hiding the grid versus
making it more transparent; and (c) the software engineering practice adopted in grid
middleware development, where the bottom up approach that is predominant [8]
conflicts with the ethos of universal accessibility that considers accessibility at
design time.
These obstacles and their impacts on universal accessibility to the grid are
discussed with reference to four application domains including collaborative
applications such as e-hospital, collaborative engineering, enterprise applications,
the media, and e-government. In collaborative applications the key obstacle for
universal accessibility to the grid is provision of interactivity while respecting
various Service Level Agreements (SLAs). Several efforts are underway to resolve this
issue [9, 21], but no versatile solutions have emerged so far. In the enterprise the
major concern is the management of an integrated data centre [10]; the key obstacle
confronted is that while already offering data-intensive computational power the grid
is quite immature in its provision of permanent storage of data. This is very much a
live issue in grid middleware development. In the media the major challenge is the
direct access to remote external devices at the grid boundaries. For e-government
accommodating various forms of interaction [11], such as government-to-government
(G2G), government-to-citizen (G2C), and government-to-business (G2B), is paramount,
whilst devoting a major focus on data semantics, not just structure.
So far universal accessibility to the grid was addressed from various perspectives.
Efforts undertaken involved: (a) the development of grid middleware supporting
interaction with heterogeneous mobile devices [12, 13]; (b) the use of operating
system mobility for configuring grid application on a PC and then migrating the
entire application together with the operating system instance onto the grid [14];
(c) the development of a shopping cart system based on the Web Service Resource
Framework WSRF [15]; (d) the design of an approach for middleware development, based
on wrapping the computational and resource intensive tasks, to allow the
accessibility to the grid via hand held devices [16, 22]; (e) the development of
common web-based grid application portals allowing the applications' users to
customize their interfaces to the grid [17, 23, 24]; (f) the development of
application models for the grid [18]; and (g) addressing security issues raised by
granting grid accessibility via various media delivery channels (such as wireless
devices) [19].
While each of these efforts towards universal accessibility to the grid does address
the problem to some extent, none of them enables a complete solution. This paper
proposes an approach, based on a metagrid infrastructure, that can potentially host
solutions to all issues related to universal accessibility to the grid. This metagrid
infrastructure was used thus far in the context of grid interoperability [3]. Our
proposed approach extends the notion of interoperability to embrace grid application
interoperability (interactivity and universal accessibility). While heavily based on
existing grid middleware services and architecture such as EGEE, Globus, CrossGrid,
GridPP and GGF [25, 26, 23, 27, 28], the metagrid infrastructure hosts one or more
target grid techologies (e.g. it has been demonstrated simultaneously hosting WebCom,
LCG2 and GT4) while also supporting its own services that provide things like
universal accessibility that the target grid technologies do not. By doing so it
firmly places the user within the metagrid environment rather than in any one target
grid environment. The user obtains universal accessibility via the metagrid services,
and the target grid technologies are relieved of the need to support direct user and
device interactions.
By way of example, services currently offered by the metagrid infrastructure include
a transparent grid filesystem [26] that supplies a vital missing component beneath
existing middleware. The grid filesystem can support universal accessibility by
supporting all forms of data access (r/w/x) in the course of collaborative
interaction (collaborative engineering and e-hospital), by providing a logical user
view of grid data (to support integration of the data centre in the enterprise), and
by helping locate (discover) data in the course of interaction in media applications.
In so doing it can improve the utility of, for example, the EGEE middleware. As
further examples, proposed future services include special purpose discovery services
to support various forms of interaction especially in media applications; and
intelligent interpreters to support e-Government data semantics.
The paper is divided in five sections. The first section introduces the concept of
universal accessibility and its relevance to the grid. The second section discusses
existing obstacles facing universal accessibility to the grid in application domains
involving social interaction. The third section overviews existing efforts towards
universal accessibility to the grid. The fourth section propose an approach for
universal accessibility to the grid based on a metagrid infrastructure and prototype
services offered by this infrastructure. The paper concludes with a summary and a
future research agenda.
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