A Technical History of the SEI

The basic features of Serpent were simple enough for use during the prototyping phase, yet sophisticated
enough for use in developing the prototype into an operational system. Serpent was
designed to be extensible in the user interface toolkits that can be supported. Hence, a system developed
using Serpent could be migrated to new technologies without time-consuming and expensive
reengineering of the application portion. Serpent consisted of a language designed for the
specification of user interfaces, language to define the interface between the application and Serpent,
a transaction processing library, an interactive editor for the specification of dialogues and
for the construction and previewing of displays, and a variety of input/output (I/O) technologies.
Serpent provided many features to address the requirements, development, and maintenance
phases of a project. For the requirements phase, Serpent provided a language and an editor to define
the user interface. For the development phase, Serpent provided a set of tools that simplify
the development of the user interface. For the maintenance phase, Serpent allowed integration of
new technologies as well as the ability to modify the user interface. Specifically, Serpent did the
following:
It provided generality in supporting a wide range of both applications and I/O toolkits through
its use of database-like schemas.
It provided a set of tools that simplified the user interface implementation process.
It encouraged the separation of software systems into user interface and “core” application
portions, a separation that would decrease the cost of subsequent modifications to the system.
It supported rapid prototyping and incremental development of user interfaces.
It facilitated the integration of new user interface toolkits into the user interface portion of a
system.
It supported both synchronous and asynchronous communication, allowing real-time applications
to satisfy timing constraints without waiting for user input.
The Consequence: Understanding the Relationship Between the User
Interface and Software Architecture
The prototypes developed during this line of worldwide research into UIMS were not used directly
for the development of software. Rather, the effort sensitized a generation of user interface
researchers to the impact of software engineering architectural decisions on the ease of modifying
the user interface, and it contributed an important concept to the discipline of software architecture
that emerged in the 1990s.
Current DoD systems, such as the Command Post of the Future, now follow this separation of
user interface. DoD Program Offices, such as Force XXI Battle Command, Brigade-and-Below
(FBCB2), often require such separation.
The SEI Contribution
Much of the work on the development of different software architecture models for user interface
construction was done by the International Federation of Information Processing Working Group
on User Interface Engineering (IFIP WG2.7/13.4) as well as by ad hoc groups of user interface
software developers. Because of Serpent, the SEI was able to make significant contributions both
in the work of IFIP WG2.7 as its members developed Presentation-Abstraction-Control (PAC)
CMU/SEI-2016-SR-027 | SOFTWARE ENGINEERING INSTITUTE | CARNEGIE MELLON UNIVERSITY 249
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