Middleware as Underwear:
Jack C. Wileden
University of Massachusetts, Department
of Computer Science
Box 34610, Amherst, MA 01003-4610 USA
Clemson University, Department
of Computer Science
Box 341906, Clemson, SC 29634-1906 USA
Toward a More Mature Approach to
Compositional Software Development
Toward Maturity and Propriety
Middleware architectures and technologies seem to have been at the center
of most recent efforts toward compositional software. As a result, a plethora
of middleware technologies have appeared over the last several years. Various
organizations (OMG, ODMG, Microsoft, JavaSoft, etc.) have been producing
increasingly elaborate middleware solutions. Is this the route to
maturity for compositional software?
We think not. Indeed, we take the position that middleware should appropriately
be considered the underwear of compositional software development. As such,
propriety dictates that it should not be the center of attention. More
specifically, we believe that middleware resembles underwear in that:
Excessive fascination with it suggests immaturity. To date, there seems
to have been an obsession with middleware and its properties. We believe
that this emphasis has been misplaced, and had inevitably led many who
are interested in compositional software to lose sight of the other points
In general, it should be kept hidden from public view. Not even seams should
be apparent. Unfortunately, contemporary middleware is often embarrassingly
visible to software users and it is far from seamless from the perspectives
both of users and of software developers.
It should never dictate, limit or prevent changes in what is publicly visible.
In compositional software terms, middleware should not determine, nor be
mistaken for, architecture. Rather, architecture should be determined at
the level of applications and expressed in applications-level terms.
No one style can be expected to meet all needs. Just as football uniforms
and tuxedos are best worn with different styles of underwear, different
software applications have different middleware needs. Attempting to provide
a single, all-purpose solution is certain to lead to chafing or lack of
necessary support. Moreover, as applications and their salient properties
(i.e., their ilities) evolve, it should be relatively easy, and
yet invisible, to make appropriate changes in middleware. Presently, an
application's choice of middleware is all to often, as noted in the workshop
description, a pervasive and irrevocable commitment.
In most circumstances, it should be as simple as possible. In particular,
while system-wide properties will necessarily impose demands upon middleware,
we do not believe that mechanisms for providing such properties are appropriately
provided by middleware.
It must be reliable. Failures can have embarrassing, and often painful,
Toward a Mature Attitude on Middleware
We believe that a truly mature discipline for compositional software development
will minimize the need for attention to middleware. Toward that end, we
advocate the following directions that, among others, may help to restore
some propriety in this area:
Formal foundations: A deeper understanding, preferably based on suitable
formalization, will be crucial to allowing multiple, minimal, flexible,
reliable and easily interchangeable middleware approaches. We have, for
example, begun to develop a formal foundation for establishing type compatibility
between software components written in different languages [BRW97]. Similar
foundations are needed for other facets of software composition addressed
by middleware. The recent FSE/ESEC workshop on Foundations
for Component-Based Software was an encouraging indication that this
direction is being pursued.
Zero language/model growth: The standard computing community approach to
any problem has always been to invent yet another language. More recently,
this approach has evolved to inventing yet another (object-oriented) type
model. Although we ourselves have been guilty of contributing to type-model
bloat in past work on interoperability [WWRT91], we are now dedicated to
crafting middleware solutions that utilize only the (already plentiful,
entirely adequate and widely used) models found in existing programming
languages [KRW97]. This approach, as exemplified by our PolySPIN interoperability
technology [KW96], not only inhibits population explosion but facilitates
both seamlessness and incorporation of legacy components in compositional
Component-based middleware: The middleware industry seems to be falling
prey to the very kind of monolithic-systems mentality that compositional
software is intended to overcome. We believe that middleware should be
based on architectures that support plugable replacement of components.
To that end, for example, our PolySPINner interoperability toolset [BKW96]
can generate middleware that utilizes any of several inter-language communication
mechanisms. Similarly, our JSpin persistent Java system [KMRW96,RTW97]
was implemented by plugging a standard Java compiler (which we had modified
in user-invisible ways) to either of two distinct persistent storage systems.
The views and positions expressed here have evolved from research that
was supported in part by Texas Instruments and the Defense Advanced Research
Projects Agency. They have also been influenced by our interactions with
numerous colleagues. These views and positions, and the way in which we've
expressed them here, however, are our own and no endorsement of them by
sponsors or colleagues should be inferred.
[BKW96] Barrett, D.J., Kaplan, A. and Wileden, J.C., Automated Support
for Seamless Interoperability in Polylingual Software Systems, Proceedings
SIGSOFT96: Fourth Symposium on the Foundations of Software Engineering,
October 1996, pp. 147--155.
[BRW97] Barrett, D.J., Ridgway, J.V.E. and Wileden, J.C., Assuring Type
Safety in Polylingual Software Systems, September 1997, 10 pp. (submitted).
[KMRW96] Kaplan, A., Myrestrand, G.A., Ridgway, J.V.E. and Wileden,
J.C., Our SPIN on Persistent Java: The JavaSPIN Approach, Proceedings
First International Workshop on Persistence and Java, September 1996,
11 pp. URL: http://www.sunlabs.com/research/forest/UK.Ac.Gla.Dcs.PJW1.pj1.html
[KRW97] Kaplan, A. Ridgway, J.V.E. and Wileden, J.C., Why IDLs Are Not
Ideal, November 1997, 8 pp. (submitted).
[KW96] Kaplan, A. and Wileden, J.C., Toward Painless Polylingual Persistence,
Proceedings Seventh International Workshop on Persistent Object Systems,
May 1996, pp. 11--22.
[RTW97] Ridgway, J.V.E., Thrall, C. and Wileden, J.C., Toward Assessing
Approaches to Persistence for Java, Proceedings Second International
Workshop on Persistence and Java, August 1997, 21 pp. (to appear).
[WWRT91] Wileden, J.C., Wolf, A.L., Rosenblatt, W.R. and Tarr, P.L.,
Specification Level Interoperability, Communications of the ACM,
34:5, May 1991, pp. 72--87. --tr7ifeQepk Content-Type: text/plain; charset=us-ascii
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