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lunes, septiembre 10, 2007

Requisitos para un escritorio semántico

Este artículo reflexiona sobre los requerimientos para hacer un sistema abierto, flexible.

Manageability - The Long Tail of Recombinant Components The Obje
project from Xerox Parc has defined a minimal set of architectural
attributes that enable dynamic interoperability (i.e. interoperability
outside of static standards). They list these "Meta -Interfaces" as follows:


One of the basic interfaces allows a component to represent a
collection if other components. For example, a file system component is
an aggregation of the components that are its directories and files.
The aggregation interface is also used for discovery, i.e., to find
other components on the network.

Once discovered, another basic agreement is how to negotiate a
connection. The discovery component includes the ability for third
party Obje components to serve as bridges. This means that two devices
can interoperate without direct physical connectivity if they can find
a device with connectivity to both or a chain of devices that can
connect them.

Data transfer

The Obje platform's basic view of interoperation is
(1) send data, (2) do
to data, and (3) sometimes, return a result. It
allows data transfer between components to occur
in ways that are not only independent of the underlying
wire protocol, but also independent of the format
of the data being transferred.

In the Obje platform,
components that are capable of sending data provide "custom
objects" that extend the behavior of potential
receivers in specific ways. While the Obje platform defines
the interface common to all custom objects, the
implementations of these objects can leverage mobile
code to provide dynamic, runtime extensibility
to new wire protocols and data formats.

User Interface/Control

Critical to successful interoperation
is that the "something" that is done
to the data depends on what component it is sent
to. The control meta-interface allows the user
to provide application semantics by directing the

Instead of having different
agreements for showing a picture on a display or
printing a page on a printer, the Obje platform needs
only the data transfer agreement. The user making
the connection provides the semantics by sending
the data, and adds additional information such
as size of print or number of copies. This is key
to allowing end-user assembly of solutions.


The final Obje component
interface returns a custom object that provides
contextual metadata about a component. The context
custom object returned by this interface provides
access to a set of attributes describing the component
that returns it: name, location, administrative
domain, and so on. The goal of this interface is
primarily to allow sense making by users, and secondarily
to allow programs to use metadata in their interactions.

At first glance one would recognize the attributes enumerated above
as being similar to technologies that have come before it (i.e. JINI,
uPnP etc). However the key distinguishing feature of the work is the
empahsis on humans being able to define the semantics:

Put another way, the programmatic interfaces define the syntax of interaction, while
leaving it to humans to impose semantics. It is the stabilization of the programmatic interfaces
that enable network effects; humans can, presumably, “understand” new components
in their environment, and when and whether to use them, much more easily
than machines can (and, it should be noted, without the need to be recompiled). This
semantic arbitration happens at the user level, rather than at the developer level as in
traditional component frameworks.

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