Towards Agile Architecture Architecture provides the foundation from which systems are built and an architectural model defines the vision on which your architecture is based. The scope of architecture can be that of a single application, of a family of applications, for an organization, or for an infrastructure such as the Internet that is shared by many organizations. Regardless of the scope, my experience is that you can take an agile approach to the modeling, development, and evolution of an architecture. Here are a few ideas to get you thinking:
Other programs in the suite include demonstration clients usable as code models and various diagnostic tools. GPSD is widely deployed on laptops, smartphones, and autonomous vehicles including self-driving automobiles and robot submarines.
It features in embedded systems used for navigation, precision agriculture, location-sensitive scientific telemetry, and network time service. It's even used in the Identification-Friend-or-Foe system of armored fighting vehicles including the M1 "Abrams"main battle tank.
The core team has been stable at about three developers, with semi-regular contributions from about two dozen more and the usual one-off patches from hundreds of others.
GPSD has historically had an exceptionally low defect rate, as measured both by auditing tools such as splint, valgrind, and Coverity and by the incidence of bug reports on its tracker and elsewhere.
This did not come about by accident; the project has been very aggressive about incorporating technology for automated testing, and that effort has paid off handsomely.
GPSD is sufficiently good at what it does that it has coopted or effectively wiped out all of its approximate predecessors and at least one direct attempt to compete with it. By the time you finish this chapter you should understand why. See [ Ray ] for Architecture term paper detailed discussion; in particular, you'll learn there about the vagaries of NMEA the sort-of standard for GPS Architecture term paper packets and the messy pile of poorly documented vendor protocols that compete with it.
If applications had to handle all this complexity themselves the result would be huge amounts of brittle and duplicative code, leading to high rates of user-visible defects and constant problems as hardware gradually mutated out from under the applications.
GPSD isolates location-aware applications from hardware interface details by knowing about all the protocols itself at time of writing we support about 20 different onesmanaging serial and USB devices so the applications don't have to, and reporting sensor payload information in a simple device-independent JSON format.
GPSD further simplifies life by providing client libraries so client applications need not even know about that reporting format. Instead, getting sensor information becomes a simple procedure call. The GPSD developers cooperate closely with the ntpd project in improving the network time service.
We are presently mid working on completing support for the AIS network of marine navigational receivers. In the future, we expect to support new kinds of location-aware sensors—such as receivers for second-generation aircraft transponders—as protocol documentation and test devices become available.
To sum up, the single most important theme in GPSD's design is hiding all the device-dependent ugliness behind a simple client interface talking to a zero-configuration service.
Thus, the API exposed to clients can remain the same even as the protocol grows new features for new sensor types. Other programs in the suite include a utility for low-level device monitoring gpsmona profiler that produces reports on error statistics and device timing gpsprofa utility for tweaking device settings gpsctland a program for batch-converting sensor logs into readable JSON gpsdecode.
Together, they help technically savvy users look as deeply into the operation of the attached sensors as they care to. Of course, these tools also help GPSD's own developers verify the correct operation of gpsd. The single most important test tool is gpsfake, a test harness for gpsd which can connect it to any number of sensor logs as though they were live devices.
With gpsfake, we can re-run a sensor log shipped with a bug report to reproduce specific problems. One of the most important lessons we think we have for future projects is that it is not enough for a software suite to be correct, it should also be able to demonstrate its own correctness.
We have found that when this goal is pursued properly it is not a hair shirt but rather a pair of wings—the time we've take to write test harnesses and regression tests has paid for itself many times over in the freedom it gives us to modify code without fearing that we are wreaking subtle havoc on existing functionality.
The Software Layers There is a lot more going on inside GPSD than the "plug a sensor in and it just works" experience might lead people to assume.
We'll describe these from the bottom up. Software layers The drivers are essentially user-space device drivers for each kind of sensor chipset we support. The key entry points are methods to parse a data packet into time-position-velocity or status information, change its mode or baud rate, probe for device subtype, etc.
Auxiliary methods may support driver control operations, such as changing the serial speed of the device. The entire interface to a driver is a C structure full of data and method pointers, deliberately modeled on a Unix device driver structure. The packet sniffer is responsible for mining data packets out of serial input streams.
It's basically a state machine that watches for anything that looks like one of our 20 or so known packet types most of which are checksummed, so we can have high confidence when we think we have identified one.
Because devices can hotplug or change modes, the type of packet that will come up the wire from a serial or USB port isn't necessarily fixed forever by the first one recognized. The core library manages a session with a sensor device.
The key entry points are: A key feature of the core library is that it is responsible for switching each GPS connection to using the correct device driver depending on the packet type that the sniffer returns.This college student resource is all about term papers, research papers, college essays and dissertations.
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A common agile practice is to perform some high-level architectural modeling early in the lifecycle. This helps to foster a common regarding your technical strategy within the team and with critical stakeholders. term papers - research and term paper help by geeks trained to assist college students.
In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer but not a particular implementation.
In other definitions computer architecture involves instruction set architecture.