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OCR for page 25
IV. INTEROPERABILITY
It was noted earlier that researchers in one discipline sometimes have
been unable to use their data network to access the data base of another
discipline. The Committee believes that OSSA recognizes this problem and
wants to ensure that future systems are compatible, at J east to the extent
necessary to achieve the required degree of interoperability.
The present-day interoperability problems will pale in significance
when compared to those of the future, especially with respect to the earth
system sciences. According to OSSA's Earth Observing System (EOS) Data
Panel, EOS will produce several orders of magnitude more data per day than
any previous mission.* That group also reported the following:
"On the scientific level, we anticipate system resource con-
f~icts arising that will demand resolution within the confines of
the data and information system. Multidisciplinary researchers
and research teams wild have needs for particular observational
sequences, while disciplinary researchers may weld have require-
ments for entirely different measurements. Both groups wild be
affected by spectacular events and the pressures (both scientific
and political) to respond."**
An Earth System Sciences Conceptual Model. One can see the complexity
of the information flows within the Earth system sciences environment by
reviewing the conceptual mode] prepared by NASA's Earth System Sciences
Committee, shown in Figure 4.*** That committee notes that changes to our
planet during the time span of human history have been modest when
compared to those that have occurred over geological timescaJes. However
* See page 8, citation from Report of the EOS Data Panel.
** Report of the EOS Data Panel, NASA Technical Memorandum 87777,
Volume Ila, 1986, p. 26.
*** Earth System Science Overview: A Program for Global Change, Earth
System Sciences Committee (Francis Bretherton, et al.), NASA, May
1986, pp. 24-25.
25
r,
OCR for page 26
human activity over the next century or two may contribute to global
changes comparable to those of geological history.
The major components, shown as boxes in Figure 4, should be conceived
of as groups of computer subroutines incorporating detailed knowledge of
the relevant processes provided by the traditional Earth-science
disciplines. The pathways (arrows) that connect these subsystems
represent the information flow necessary to describe the interactions
among them. The ovals and the attached arrows denote inputs from, or
outputs to, an external environment.
The use of models will help scientists to understand better the
multiplicity of interactions among the Earth System components and to aid
in predicting the future evolution of the system in response to selected
changes in input variables. The mode] also illustrates the emphasis being
pi aced on an integrated view of the interactions of the lithosphere; the
physical climate system, including the atmosphere, oceans, and J and
surfaces; and the biosphere, coupled to the other components through the
biogeochemica] cycles. This integrated view is a fundamental aspect of
Earth System Science and tends to indicate a continuing and increasing
need for cross-discipline and multi-discipline data flows.
In both solar terrestrial physics and planetary science, the science
requirements for missions planned for the 199Os will be different from
those in the past two decades. By 1989 spacecraft will have visited two
comets and all of the planets of the solar system except Pluto. The first
missions were primarily missions of discovery while the missions in the
199Os wild concentrate on increasing understanding. Missions are planned
to Venus, Mars, Jupiter, a comet and an asteroid. The scientific problems
in planetary science wild require the talents of experts in a variety of
disciplines. For instance, one of the most intriguing features of the
Jovian system is lo and its interactions with corotating Jovian plasma,
which is of loan origin. An understanding of the phenomena associated
with these interactions requires the expertise of planetary geologists,
atmospheric scientists, and plasma physicists. In solar terrestrial
physics, the emphasis will be on understanding the flow of energy and
momentum through the coupled systems of the solar wind, the magnetosphere
and the ionosphere. This will require coordinated multi-spacecraft,
mu~ti-instrument and ground observations. In astronomy and astrophysics
the 199Os will begin an era of observatories in space. Late in this
decade the Rubble Space Telecope wild be launched. The Hubble Telescope
plus the Space Telescope Science Institute wild constitute an observatory
like those on earth, only with the telescope above the atmosphere.
These changes and others indicate that OSSA faces a significant chal-
Jenge in the development of interoperable information systems to support
forthcoming interdisciplinary and multidisciplinary missions. There are
no simple solutions; the issue is:
Issue #2. How can interface requirements be established that would
ensure interoperability with a minimum of standards?
26
OCR for page 27
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OCR for page 28
Interconnection and Interoperability of Information Systems. Certain-
~y the easiest way to achieve interoperability is to have one system with
identical or compatible hardware and software throughout. Practically,
though, there are many reasons for keeping information systems separate,
such as the need to keep old but relatively cheap systems in operation
rather than lose the data or have to move it to another system. There-
fore, there will always be a number of systems supporting OSSA's missions,
and it appears there wild be an increasing requirement for interoperabili-
these systems. OSSA already knows that ease in
iJitv will depend directly on the degree of homogen-
ty among a number of
achieving interoperab ~
eity of its systems: the more alike they are the easier it is to intercon-
nect them. Unfortunately, OSSA information systems differ substantially
in their data base formats and languages, their operating systems, and the
composition of their network protocols. OSSA, in concert with the Office
of Space Tracking and Data Systems (OSTDS), GSFC, and JPL, has been
addressing several aspects of the interoperability problem. Examples:
On-Line CataJoq Activities. The trend toward decentralized and
-
distributed data bases is causing increasing difficulty for users
who need information about the data bases or data from them. The
NSSDC On-Line Data Catalog System (NODCS), consisting of the
Central On-Line Data Directory (CODD) and the Distributed Data
Catalog System (DDCS), is being developed to alleviate these prob-
Jems. Once a user has decided to access a particular catalog in
the DDCS, it will in some cases be possible to gain access auto-
matical~y through CODD. In other cases, it will be necessary to
follow procedures that CODD wild provide. However, there is no
mechanism planned to allow a user in any catalog to gain direct
access to data in any other catalog within the DOGS, since the
interface languages and data query systems differ and the systems
are structured to be top-down and menu driven. The Committee felt
this was a useful first step, but that further efforts are needed,
perhaps through the provision of gateways, to ensure interoperabil-
ity across the ocean, land, climate, and planetary data systems
and perhaps among other science data systems and odder meteorolog-
ical and earth-observation systems.
Data Interchange. Both OSSA and OSTDS have strong interests in
(and have been heavily involved in) the development of Standard
Formatted Data Units (SFDU) as a means of facilitating both data
transfer and interoperabiJity among data systems. Most data
formats now are mission-specific, but NASA wants a transition to
generic structures and processes, since the goals are to maintain
the data sets and relevant information in a consistent form and to
enable users to obtain data with no manual intervention. OSIDS
and GSFC have represented NASA on the Consultative Committee on
Space Data Systems (CCSDS), a standards body that concentrates on
standards for interface protocols including the SFDU. JPL also
has done quite a Jot of work in this area, including the develop-
ment of standards that are consistent with the CCSDS recommenda-
tions regarding the SFDU. OPE's Planetary Data System will serve
28
1.
OCR for page 29
as the SFDU test bed for the planetary community. JPL also plans
to require the use of the SFDU in other missions.
Since the less two interconnected systems are alike the more they will
need conversions across the various layers of the information systems
architecture, OSSA must concentrate on eliminating differences among its
systems. It will not be possible for OSSA to change its older systems, so
the problem is not going to go away for many years. However, the planning
must begin now.
The Department of Defense (DoD) Experience with Transport Protocols.
It is useful to consider the experience of the DoD, which encountered a
similar problem in the 1970s, a period that saw the evolution of a number
of new networks, using many different protocols. The DoD's Advanced
Research Project Agency (ARPA) established a network--ARPANET--in the
early 1970s to serve as a research vehicle and testbed for computer
communications protocols. In 1978 the agency concluded four years of
developmental testing on a Transmission Control Protocol (TCP) and an
subsequently were mandated for u~ ac
`, a
Internet Protocol (IP), which . ~
standards throughout the DoD. It has been concluded that the momentum for
the DoD program to establish interoperability among its networks resulted
primarily from the directed use of TCP/IP.
In the early 19SOs, the National Bureau of Standards (NBS), in coop-
eration with the DoD, industry, and the International Standards Organiza-
tion ("ISO"), developed a new Transport Protocol (TP-4) and a new Inter-
network Protocol.* While DoD's TOP and IP have proven to be highly
effective, and IP and the "ISO" Internetwork Protocol can easily be made
compatible, TOP is not compatible with TP-4. TP-4 and the Internetwork
Protocol were approved by the "ISO" as Draft International Standards in
1983 and 1984, respectively. Since commercial vendors normally consider
Draft International Standards to be ready for implementation, there has
been some expectation that commercial equipment manufacturers will employ
the "ISO" standard protocols. If this were to prove true, organizations
that employ other standards would find it difficult to find commercia1ly-
avaiJable, off-the-shelf hardware for their networks. However, industry
has not produced TP-4 products as rapidly as had been expected. As a
result, DoD has indicated that it will adopt TCP/IP and TP-4/"ISO" IP as
coequal standards after a satisfactory demonstration of the Jatter's
suitability for use in military networks. A final commitment will be
deferred until the demonstration has been evaluated and TP-4 products are
commercially available.**
In this report, "ISO" represents the International Standards Organiza-
tion and ISO represents the OSSA's Information Systems Office.
** See Transport Protocols for Department of Defense Data Networks, a
.
report of the Committee on Computer-Computer Communications Protocols,
Board on Telecommunications and Computer Applications, NRC, National
fContinued on p. 30]
29
OCR for page 30
This approach will provide maximum flexibility for the DoD, by enab-
ling it to determine whether to convert to TP-4 or to remain with TCP,
depending on which standard proves to be the popular choice among equip-
ment manufacturers. In either case, the DoD will obtain the benefits of
standard commercial products at an early date. Once commercial products
are available, development, procurement' and support costs should be low-
er. The main points illustrated by the DoD experience are: (~) adherence
to some standard is necessary to achieve (inter alia) interoperability,
and (2) the decision to adopt or not adopt protocols that have been
promoted by national and international voluntary standards organizations
can be driven as much by factors such as product availability as by the
goal of interoperability.
Onen Systems Interconnection (OSI) Architecture. It should be noted
~ ,
that TP-4 is part of a broader scheme called the OST Architecture. The
"ISO" began developing this architecture in the late 1970s, at the same
time the International Telegraph and Telephone Consultative Committee
(CCITT) began to develop its own OST reference model. By 1984 the CCITT
had adopted the same language as the "ISO", and the reference model now is
known as International Standard ISO 7498 and CCITT Recommendation X.200.
As an indication of the seriousness with which the OSI architecture
being regarded throughout government and industry, OSSA should consider
the following recent events, which also tend to indicate that OSSA might
wish to orient its thinking toward eventual migration to TP-4.
Establishment of the Corporation for Open Systems (COS). In early
January 1986, a group of computer and communications manufacturing
companies incorporated COS in the Commonwealth of Virginia as a
nonstock, not-for-profit membership corporation. The purpose of
COS is: "to provide an international vehicle for accelerating the
introduction of interoperable, multivendor products and services
operating under agreed-to OSI, Itegrated Services Digital Network
(ISDN) and related international standards to assure acceptance of
an open network architecture in world markets." COS proposes to
achieve its objectives through establishment of conformance and
interoperability test programs to verify member-companies' product
compliance with the "ISO" OSI standards and by identifying areas
"Continued from 0.29]
Academy Press, Washington, D.C., February 1985. The report notes that
the services provided by TOP and TP-4 are functionally quite similary,
but that some functions are provided in significantly different ways
by the two protocols. This includes data transfer interface, flow
control, connection establishment binding, and out-of-band signals.
It was estimated that an experienced programmer would require about
six months to design, implement, and test modifications of the three
major, higher-level, DoD protocols (fide transfer, mail, and Telnet)
to work with TP-4.
30
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in which standards development needs to be accelerated. By early
1987, COS membership comprised 61 computer hardware, communica-
tions, and software companies; computer and communications ser-
vices providers, computer and communications users, and companies
involved in the development of underlying technologies. The total
includes three British companies, one Italian company, and agen-
cies of the British and Canadian governments.*
Establishment of the Government OS] Users Committee. In early
. .
September 1986, the government announced establishment of the OST
Users Committee, whose goal is to determine an OS] standard for
the government. The government also is considering a revision of
its procurement policies to prohibit the purchase of commercial
products that do not conform to the standard, which the committee
hopes to develop during 1987. Fifteen agencies, including NASA,
belong to the committee.**
Considering these recent developments, it would appear that OSSA's
future strategy has been set, but that it stir] needs to concern itself
with the '.tactica1" problems of dealing with its older networks and, for
those networks that require interoperabiJity, the establishment of a clear
migration path to the OS] architecture.
The following factors (and perhaps others) need to be examined, in
order to develop criteria against which OSSA can identify and evaluate
suitable options:
functional and operational specifications (that is, will the pro-
toco] designs meet OSSA's present and future operational needs?;
interoperabiJity requirements (for example, must OSSA networks be
interoperable at the applications level as well as at the network
access level?;
minimum procurement, development, and support costs; and
ease of transition (migration) to new protocols.
As with the issue of centralization, the Committee believes that OSSA
is justified in taking a rather cautious approach to the interoperability
Information supplied by COS, January 1987.
** The other 14 members of the Government OS] Users Committee are the
Departments of Agriculture, Commerce, Defense, Energy, Health and
Human Services, Housing and Urban Development, Interior, Justice,
Labor, Transportation, and Treasury; the Environmental Protection
Agency, the General Services Administration, and the Office of
Management and Budget.
31
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issue. While it is clear that cross-discipline data accessibility wild be
increasingly important in earth-oriented discipline programs, it is not so
clear that this will be the-case for programs in space physics, solar
physics, astronomy and astrophysics, and planetary science. It is impor-
tant to determine as soon as feasible which of the disciplines require or
can benefit from coordinated or common data systems and which do not
require coordination. To force commonality where it is not needed runs
the serious risk of increasing costs and hampering the scientific work.
Resolving these questions requires working with the discipline program
managers and scientists.
For those new networks that wild require interoperability, it would
appear the proper approach would be to focus attention on non-proprietary
standards that are in place and emerging for high-speed data networks.
There is no evident need for OSSA to develop new standards or technolo-
gies, but it needs to develop a strategy for the adoption of standards so
that its future networks wild be compatible with those of the agencies
with which it wild need to interoperate, such as the DoD, the National
Oceanographic and Admospheric Administration (NOAA), the National Science
Foundation (NSF), the Department of Energy (DOE), and other agencies with
evolving networks.
The Committee understands that OSSA is considering use of the NSFnet
for data as weld as electronic mail distribution to researchers. Within
the time-frame currently being assumed for the NASA environment, there is
a reasonable expectation that the evolving NSFNet will be able to support
the data rates implied by the l- and lO-Mbps rates discussed above. The
current short-term plans call for networking technology based on T!
carrier facilities (~.544 Mbps) and internet protocol (IP) routers--the
switches of the NSFNet backbone--capabJe of 1,200 maximum-length packets
per second. The limitations of current networking are not in the
transmission facilities, which can go to one gigabit per second (Gbps)
rates, but in the switches, gateways, and packet handlers. The
development of these units to support fiber speeds is happening slowly.
However, the foregoing assumes that the information that flows onto
the NSFNet is created by networks that support the NSFNet protocol family
-- namely DoD's TCP/IP, evolving to the "ISO" TP-4, which has also been
recommended by the CCITT. Many of the constituent NASA networks, such as
the Space Physics Applications Network (SPAN), do not conform to these
standards. This creates a variety of problems. The most critical is the
inability of researchers to reach across from, say, the ocean data net-
works to the Earth science databases. also, the lack of clearly defined
standards in electronic mail, file transfer, etc., which is common across
the OSSA discipline networks, makes it difficult, if not impossible, for
researchers to communicate with each other. In addition the app~ication-
level gateways required would severely restrict the network throughput
across such incompatible networks. Keeping in mind the approach being
taken by the NSF, the DoD, and other agencies that have elected to stay
with TCP/IP but eventually to migrate to TP-4, OSSA might want to consider
a similar strategy in future information systems acquisitions.
32
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Based on presentations on procurement made to the Committee, the
information systems procurement process appears to be one that follows the
sequence in which designs and design specifications are developed
internally to a fairly detailed, well-coordinated level and then issued
for competitive procurement. The process described by the presenters is
quite lengthy, consuming from one to three years before a definitized,
coordinated specification is generated. During the process, some dialogue
takes place with potential contractors, but for competitive purposes many
details are closely held internally within NASA. Contractors usually are
given the opportunity to review and comment on the specification and
statement of work. However, once the formal Request For Proposal (REP)
has been issued, contractors must respond to a "design-to-specification"
requirement in a relatively short time. This approach often results in
systems with technologies that are not state-of-the-art, and architectures
that are not cost-effective in terms of the system life.
NASA presenters indicated that several significant NASA information
system procurements have been issued or are planned to be issued using
this approach. These include the Technical Management Information System,
Program Support Communications Network, and Earth Observing Information
System.
A Procurement Strategy to Foster InteroperabiJity. The Committee
suggests that an alternative information systems procurement strategy be
considered--one that has been used successfully by NASA on many large
space procurements--involving a competitive Concept Design Phase (COP)
based on performance requirements that will lead to design specifications.
Some of the characteristics and benefits of this approach are the
following:
Effort "Multiplier." It is expected that competing contractors
wild commit substantial resources during the COP, which fact wild
permit the project to move forward further and faster than would
be possible with government funding alone.
Enhanced Options. OSSA will be provided several design solutions,
reflecting both the technological state of the art and the
creativity of the competing contractors, enabling it to select
system and subsystem design configurations that wild do the job at
the best price. This would enable OSSA to request and evaluate
proposals that include provisions for a migration path to TP-4.
Industry Perspective. OSSA will J earn the industry's perspective
on system costs and alternatives.
Improved User Support. OSSA will obtain a better product by
offering industry the opportunity to participate in its dialogue
with the users on the mission to be satisfied. Included in this
dialogue would be users who must access the system indirectly.
33
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Faster System Development. OSSA will have the opportunity to
prototype systems or elements of systems rapidly, as a step in
shortening the development of design specifications (by intro-
ducing user requirements to engineering design, for example, as a
step in the specification generation process).
The Committee believes that a procurement strategy and process foster-
ing competition as early as possible in the acquisition cycle, particular-
~y on large information system procurements, would enhance the probability
of satisfying user and mission requirements in a more timely manner' with-
in life cycle cost-effectiveness goals.
The adoption of common standards among the research networks of major
agencies such as NASA allows users to have maximum flexibility with res-
pect to access to their data, use of common campus networks and facili-
ties, use of alternative access routes that provide flexibility, and use
of nationally-supp~ied communications facilities. We believe OSSA is
taking the proper approach to this issue. Time is the enemy now, however,
and OSSA is faced with critical choices that must be made before the
massive flood of data from the new NASA initiatives and the desire of
researchers to access such data both increase the frustration of the users
and make it difficult to convert from the status quo to state-of-the-art
information systems that satisfy NASA's and the users' needs.
34
Representative terms from entire chapter:
planetary science
