Software Architecture in Practice: the Luther Architecture
Workers involved in the maintenance or operation of large vehicles (such as tanks and aircraft) or portions of the industrial infrastructure (such as bridges and oil rigs) have great difficulty using computers to support their tasks. Because the object being maintained or operated is large, work on it must be in situ, outdoors or in special structures, neither of which is conducive to desktop computing. In particular, a computer solution usually involves a wireless infrastructure and either a handheld or a hands-free computing device.
Inmedius is a company that was established in 1995 as an outgrowth of Carnegie Mellon University's Wearable Project (see the sidebar History of Wearable Computing) to provide support for front-line maintenance and operation workers. Initially producing one-of-a-kind solutions for its customers, as the company grew it realized the necessity for general solutions that could be quickly tailored to a customer's needs.
The front-line worker does not work alone but requires a great deal of back-office support. Problem reports must be collected and work must be scheduled to enable repairs to be made, replacement parts must be taken from inventory and re-ordered, and maintenance records must be analyzed. All of this work-flow management requires integrating the front-line worker with the back-office worker who has access to a desktop computer.
The Luther architecture was designed to provide a general framework within which Inmedius could provide customized solutions for the maintenance problems of its customers. It is based on the Java 2 Enterprise Edition (J2EE) architecture, so becomes an application of the general J2EE/EJB framework (discussed in Chapter 16) to an environment where the end user is connected over a wireless network and has a device with limited input/output capabilities, limited computational capabilities, or both.
History of Wearable Computing
Arguably, the first wearable computer was the wristwatch. It was invented around 1900 and at first was unable to compete with the pocket watch. Why would someone wear a watch on his wrist when his existing pocket watch kept good time and could be accessed quite freely? However, during World War I, the British Army issued wristwatches to its troops so that they could synchronize attacks while keeping their hands free for weapons. Suddenly, it became fashionable in Britain to show support for the "boys in the trenches" by wearing wristwatches. Now, of course, you rarely see a pocket watch.
By the early 1990s, technology had begun to support the wearing of digital, full-function computing devices. One organization investigating the use of these devices was the Wearable Group of Carnegie Mellon University headed by Dan Siewiorek. They viewed a wearable computer as a tool to support workplace functions, with the workplace epitomized by locales where aircraft and other large vehicles were maintainedout of doors or within large buildings such as hangars or railroad roundhouses.
The focus on use in a workplace meant that ease of use and design sophistication were primary. The Wearable group conducted experiments with computers designed and constructed by students in actual workplaces. The success of these experiments created the demand that Inmedius was organized to exploit.
A second group, operating at the same time and centered at the Media Laboratory of the Massachusetts Institute of Technology, styled themselves "borgs." They viewed the wearable computer as a consumer product designed to change the lives of those who wore it. They wore their computers all of the time and were interested in innovative uses of them and in memory support applications. One example was using the conductivity of the skin as a network medium and having two computers exchange business cards when their wearers shook hands.
By the late 1990s, the two groups were collaborating to make wearable computers a viable academic discipline. Various commercial companies had begun to offer computers and head-mounted displays, and large commercial concerns had begun to show interest. Now, with the increasing miniaturization of hardware and the increasing sophistication of software (as evidenced by this chapter), wearable computing can only become more prevalent.
17.1 Relationship to the Architecture Business Cycle
Figure 17.1 shows the Architecture Business Cycle (ABC) as it pertains to Inmedius and the Luther architecture. The quality goals of re-usability, performance, modifiability, flexibility of the end user device, and interoperability with standard commercial infrastructures are driven, as always, by the business goals of the customer and the end user.
Figure 17.1 The ABC as it pertains to Inmedius and Luther
Influences on the Architecture
The next sections elaborate on the things that influence the Luther architecture.
Inmedius's business is providing computer support for front-line workers. Figure 17.2 shows such a worker utilizing one of the hardware configurations supported by Luther applications. The worker is performing an industrial process, the steps of which are displayed on the head-mounted display apparatus that he is wearing. The computer is worn on the user's chest and uses a dial as its primary input device. The process is described in a manual stored on the back-office computers, and the manual pages are served to the worker as various steps of the process are completed, which can number more than 500. The worker reports the results of portions of the process to the back office via the system. A part may be replaced, for example, and the part number is reported so that the inventory can be adjusted and any quality-control ramifications analyzed.
Figure 17.2 A field service worker using the Inmedius solution.Å@Courtesy of Inmedius Corporation.
The workers may need to use one or both hands to perform the process, so those hands are not available for computer input. Further, workers may need to be mobile to carry out the tasks.
Different processes and customers may require different hardware configurations because requirements, such as mobility and the number of hands available for computer input, can vary.
If the Luther architecture can facilitate the development of complex enterprise solutions in a fraction of the time they take to develop as standalone, "stovepipe" systems, Inmedius gains a significant competitive advantage. To achieve this, the company must meet increasingly shorter time-to-market for enterprise solutions. The development cycles for these solutions have to be in the low single-digit months for Inmedius to remain competitive in its target markets.
Solution development must be performed quickly and frugally by a few tens of engineers. The quality of the delivered solution must be high to ensure customer satisfaction. Also, the delivered software artifacts must be easily modifiable so that corrections and enhancements require little effort by Inmedius and do not compromise the integrity of the original solution's architecture.
Luther has been influenced by developments in both software and hardware. As we discussed in Chapter 16, J2EE provides enterprise solutions for commercial organizations. It was a good fit with the Luther requirement to interoperate with back-office processes. J2EE also facilitates the packaging of domain-specific application capabilities into re-usable components that can be combined in different ways.
In addition to software influences, emerging hardware technology has influenced Lutherspecifically, in the need to support small wireless computers with voice input capabilities and high-resolution, head-mounted displays. On the other hand, differing environments may require different types of devices, each with its own set of capabilities. This imposes a requirement that Luther be flexible with respect to the types of user interfaces supported.
Influences on the Organization
The influences of Luther on the organization are in the areas of organizational structure, software developers' experience, and business approach.
Prior to Luther, Inmedius was a solution factory, with each solution developed as a stovepipe application for a specific customer. Organizationally, the Solution Group was the largest engineering group in the company. Luther's development created the need for a Products Group (containing a Component Development Group) to engineer and maintain the domain-specific component capabilities the Solution Group uses to create its solutions for customers. The Product Group is concerned with generalized capabilities for markets, whereas the Solution Group is concerned with specific applications for individual customers. This is an instance of a two-part organizational structure for software product lines, as described in Chapter 14 and illustrated by CelsiusTech case study in Chapter 15.
Software Developers' Experience
Prior to Luther, Inmedius was staffed with experienced and sophisticated software developers, who nonetheless had a number of new criteria to satisfy in Luther's development:
Learning the Java programming language
Becoming Sun Java Programmer Certified
Learning the J2EE application architecture
Learning how to package capabilities as J2EE/EJBs
Learning how to create Java servlets and JavaServer Pages
Learning how to use the various J2EE services provided by J2EE implementations
The Luther architecture has had a dramatic effect on the way Inmedius does business. As we said in Chapter 14, single-system solutions require a large amount of resources, and this resource drain and the stovepipe mentality associated with single system development inhibits global thinking. The move to a product line based on Luther enabled Inmedius to begin thinking about product lines instead of focusing on individual systems. Furthermore, as we saw with CelsiusTech, new markets became available to Inmedius that could be seen as generalizations of existing markets, not only in a business sense but also in a technical sense.