Presents your 
XML E-NEWSLETTER for January 22, 2003

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MAKE APPLICATIONS MOBILE WITH XML DATA

One of the hottest current technology trends is mobile applications.
Mobility empowers field workers to accomplish more by expanding their
toolset to include powerful devices and applications. One aspect of these
applications is XML, where there are some special considerations for mobility.

SIZE MATTERS

One of the immediate concerns about XML in a mobile environment is the
size of the XML payload. Whether the field worker is receiving new data or
is sending updates, the XML payload may be quite large. In cases where
the data set is large, there are special considerations for how to move
the data from one place to another. The reason for this is
two-fold--capacity and bandwidth.

CAPACITY

If you are sending or storing too much XML data, then the device will
become unusable. To solve this problem, many mobile applications will
truncate the XML payload by extracting only the necessary components. 
Another component of the solution is to store only what's necessary and to move
the data often. This is because many devices can fail and lose all data
stored on them. In addition, by moving the data frequently, smaller 
amounts of data are stored on the device.

BANDWIDTH

Bandwidth is determined by how the device is connected to the network.
There are many connection options including wireless links, Wi-Fi, and
hardwired connections.

Wireless links grant the ultimate in mobility, but at the expense of
reducing the amount of bandwidth. Wi-Fi is a protocol for allowing
high-bandwidth connections within a set environment. While Wi-Fi gives 
a lot of bandwidth, it's only within a certain range of the Wi-Fi receiver. 
Finally, hardwire connections usually give the most bandwidth, allowing the most
data to flow.

TIMING

Whether you move data all at once in a batch-style system or
periodically in a real-time system can be important. With a batch 
system, you are relying on the device to store more data and to move more
data in a single transfer. In a real-time environment, each time data is entered
or dispatched, a transfer occurs. Batch systems move more data less frequently,
while real-time systems move less data more frequently. The approach is
often based on both capacity and bandwidth.

WHICH IS BEST?

Ultimately, it comes down to connectivity and capacity. If your devices
have a lot of capacity and Wi-Fi connectivity, then you have a lot of
flexibility in your approach to moving XML data. On the other hand, if 
you are working with wireless devices with small capacity, but need to 
handle lots of data, a more real-time approach may be a good fit. That
way you distribute the larger data set moving across the slower link.

AFFECT ON XML

One of the affects this all has on XML is that the approach you use to
move data can change the way you describe the data. For example, if you
need to move data in a batch rather than in real-time, you may describe 
the batch of records differently than the real-time records. In addition, 
on devices with limited capacity, you may only send essential elements,
which can be identified by placing special attributes in your XML.

Brian Schaffner is a senior consultant for Fujitsu Consulting. He
provides architecture, design, and development support for Fujitsu's 
Telcom360 group.

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