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The  Impact  of  Reuse  Library  Interoperability  up on  a  Software


                                       Component Industry



                                              James W. Moore

                                    IBM Federal Systems Company

                                         800 North Frederick Ave.

                                         Gaithersburg, MD 20879

                                             Tel:  [phone]

                                    Email:  [e-mail]

                                            Fax: [phone]



                                                    Abstract


      Recent work in interconnecting software reuse libraries has implications which suggest that
  a software component industry may have much greater diversity than previously expected. This
  paper will briefly describe some of the work and examine its implications upon the industry.


  Keywords:  Software reuse, reuse libraries, reuse industry, reuse economics, interoperability,
  standards.


  Workshop Goals: Improve understanding of the requirements for a software reuse industry.


  Working Groups: Reuse management, organization and economics.



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1      Background



Jim Moore was the original System Architect for IBM's role asa prime contractor in the ARPA
STARS program. Currently, heis resp onsible for all of IBM's technology refinement efforts on the
program. He served as IBM's technical lead in the founding of the ASSET library.  He is a charter
member of the RIG and serves as the chairman of its Executive Board.


(See note at end regarding acronyms.)



2      Position



Recent work in interconnecting software reuse libraries has implications which suggest that a soft-
ware component industry may have much greater diversity than previously expected.



    fflThree government-sponsored reuse libraries (CARDS, ASSET, and DSRS) have recently con-
       ducted experiments in interoperation and plan an operational capability in the fall of 1993.


    fflThe ARPA STARS program has demonstrated an architectural prototype, the Library Inter-
       operability Demonstration (LID), which shows how monolithic reuse libraries can be segre-
       gated into three distinct functions.


    fflThe Reuse Library Interoperability Group (RIG) has recently completed the first of a planned
       series of proposed standards intended to facilitate interoperability.


    fflThe ASSET library is creating a National Software Reuse Directory.



Each of these events suggests ways in which a software component industry might evolve.


ARDS/ASSET/DSRS (CAD) interoperation marks the end of an era where various reuse library
operators were attempting to position themselves as the single,b est library that everybody should
use. Each of the participating libraries (it is anticipated that more will join)provides a remote index
of components which may be obtained through the other libraries.  The other libraries incorporate
the descriptions of those components within their cataloguing mechanism just as if the component
were local. When a user attempts to extract the component, a copy is transmitted from its library
of residence to the user's library. Although the technical effort to achieve interoperation is non-
trivial, the key accomplishment is the resolution of various business issues which were obstacles to
sharing.  The most significant result, however, is the evolution toward a cultural perception that
reusable components are best stored in a network of cooperating, specializing librariesrather than
a single, general-purpose one. This perception is essential to the creation of a viable industry. After
all, a small contractor working on a large pro ject may need access to several libraries: its own, the
prime contractor's, and the customer's as well as other libraries for performing make versus buy
decisions and obtaining specialty components outside its ownfield of expertise.


The ARPA STARS LID demonstration [1 ] signals the impending end of an era whenreuse library
mechanisms were constructed as single, monolithic tools. The LID prototype segregates a library
into three distinct layers:



    ffla storage layer which safely preserves the softwarecomp onents



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    ffla catalog layer which adds value by indexing the comp onents in ways intended to be useful


    ffla user interface layer which presents the catalogs and other services to the user.



The demonstration shows that each of these layers can be implemented by separate tools commu-
nicating via high-speed links. In particular, the demonstration shows two different catalogs which
don't actually store any components; instead they delegate the storage function to a separate server
accessible by high- speed telecommunications links. In addition, the demonstration shows two dis-
tinct  user  interfaces, a  text-based  mechanism  and  a  graphics-based  mechanism, which  each  can
access either of the catalogs. Finally, the demonstration shows that a componentcan b e "copied"
from one catalog to another by means of transmitting only thedescriptive information; the com-
ponent itself remains unchanged and unmoved in the storage server. The demonstration illustrates
that the business of operating a reuse library is actually at least three distinctbusinesses which
can be individually pursued:



    fflSafely storing and preserving components for future access.


    fflPerforming value-added indexing of components selected from various storage libraries.


    fflProviding powerful user interfaces which allow access to various catalogs.



Obviously,the kind of interoperation described in the previous sections can not be achieved without
widespread agreement on suitable interfaces. For two years, the RIG has been working on standard
interfaces for the interoperability of reuse libraries.  Earlier this year, the RIG published its first
proposed standard, the Basic Interoperability Data Model (BIDM) [2],  describing the minimum
amount of information which a reuse library shouldb e able toshare with other libraries.  Addi-
tional work proceeds toward the formulation of more comprehensive data models, protocols for the
transmission of models and components, meta- models to enable communication among dissimilar
data models, interoperability metrics, and characterization of existing libraries and mechanisms.
Groups within the IEEE and the AIAA are also pursuing related work.  The significance of this
development is the additional safety that it provides for entrepreneurs interested in entering the
marketplace.  A  marketplace  with  a  stable  set  of  standards  significantly  reduces  the  risk  for  a
new business. The standards can be viewed as defining electronic niches where businesses may be
founded with a high degree of assurance that they will be able to conduct electronic commerce with
other businesses and customers. The current efforts on standardization serve to define niches ap-
propriate to the interoperability model exemplified by the CAD  interoperability. Additional work
is needed to standardize the richer interoperability implied by the LID demonstration.


The National Software Reuse Directory (NSRD) is anew pro ject of the ASSET library.  ASSET
was founded on the premises that it should be national in scope and part of a distributed network
of libraries [3].  One strategy for accomplishing this goal is to act as a "reference library" to assist
users in locating other libraries which may specialize in their areas ofinterest.  The NSRDis a kind
of software "yellow pages" intended to facilitate this kind of search.  The NSRD is a collectionof
information regarding software assets contained in various, different libraries or from other sources.
The information within the NSRD is that specified by the RIG's BIDM. The concept is that various
component producers or library operators will provide BIDM descriptions of assets tob e listed in
the NSRD. Users will search the NSRD for comp onents of interest, thereby learning of the libraries
which contain those components.  At this time,  the user would have to access the listing library
directly,  but in the future,  interoperability mechanisms will permit direct access to the libraries
containing the components. The primary significance of this development is that it points toward



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a distributed electronic marketplace where some libraries specialize inparticular areas of expertise
and others provide services to assist users in locating the specialized libraries. The current NSRD
also points the way toward future commercial indexes which add value by selecting, listing, and
perhaps reviewing, certifying or evaluating components which are actually stored elsewhere.



3      Comparison



Taken as a group,the efforts described above imply a sea change in the structure of a reuse industry.
Instead of an industry dominated by one or two large government-sponsored libraries, we can foresee
an industry providing niches for many small entrepreneurs:



    fflThe interoperability efforts provide a basis for a network of libraries as opp osedto the previous
       concept of one or two large, all-inclusive libraries.


    fflThe LID demonstration shows that libraries of the future need not be as monolithic as the
       libraries of the past.  In fact, it seems that the storage of assets, the cataloguing of assets,
       and the presentation to the user may all be distinct businesses.


    fflThe ongoing efforts for standardization reduce risk in entering the business. Previously, any
       entrepreneur who might try to add value to an existing monolithic librarywas deterred by
       the simple fact that the library might change its external interfaces at any time.


    fflThe  NSRD  is  both  a  first  step  toward  the  specialization  of  library  roles  and  a  first  step
       toward an infrastructure promoting commerce in services as well as components. Both steps
       are radically different from prior models where users dealt solely with a centralized library
       providing all services itself.



References



[1]  P. Berggren, "Library Interoperability Demonstration," in Proceedings of the DARPA Software
     Technology Conference, (Salt LakeCity, Utah), April 1993.


[2]  "Basic  Interoperability  Data  Model,"  Tech.  Rep.  RPS-0001,  Reuse  Library  Interoperability
     Group, 1993.


[3]  C. W. Lillie and J. W. Moore,  "Asset Source for Software Engineering Technology (ASSET)
     Software Reuse and Reengineering," in NISQP Software Reuse and Reengineering Conference,
     (Alexandria, VA), April 1991.



It would be improper to leave this subject without acknowledging the seminal role of the ARPA
STARS program in enabling the advances described above.  To wit:



    fflSTARS wrote a mission statement for ASSET which made it the first government-sponsored
       library chartered with the responsibilities to foster a reuse industry and to function as a node
       within a distributed network;


    fflSTARS developed the ALOAFtechnology which was the basis of the LID demonstration;and


    fflSTARS was a charter member of the RIG and has supported its efforts b oth technically and
       financially.


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4      Acronyms



Acronyms pervade both government and technology and reuse is no exception.  Since most ofthe
efforts are better known by their acronym than their name, I  have chosen to use the acronyms in
the body of the paper and explain the names here:



AIAA      :  American Institute of Aeronauticsand Astronautics


ALOAF        :  Asset Library Open Architecture Framework


ARPA       : (Defense) Advanced Research Projects Agency


ASSET       :  Asset Source for Software Engineering Technology


BIDM       : Basic Interoperability Data Model


CAD      : CARDS/ASSET/DSRS


CARDS        :  Central Archive for Reusable Defense Software


DSRS      :  Defense Software Repository System


IEEE     :  Institute of Electrical and Electronic Engineers


LID    :  Library Interoperability Demonstration


NSRD       : National Software Reuse Directory


RIG     : Reuse Library Interoperability Group


STARS       :  Software Technology for Adaptable, Reliable Systems



5      Biography



Jim Moore is a Senior Engineer at IBM's Federal Systems Company.  He currently works on the
ARPA STARS program where he served as IBM's technical lead in the founding of the ASSET
library.  He is a chartermember of the RIG  and serves as the chairman of its Executive Board.
He  holds  BS  and  MS  degrees  from  North  Carolina  and  Syracuse, respectively  and  is  a  member
of  the  IEEE Computing  Society  and  the  Association  for  Computing  Machinery.   He serves  as  a
member of the Ada Federal Advisory Board and as a member of the U.S. delegation to ISO-IEC
JTC1/SC22/WG9, the group responsible for Ada standardization.



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