Methodology范文-dissertation Methodology范例-Features of the Sys

Methodology范文-dissertation Methodology范例 Features of the System Engineering Process Activities (SEPA)
Methodology
K. Suzanne Barber, Thomas J. Graser,
Stephen R. Jernigan, and Brian J. McGiverin
The Laboratory for Intelligent Processes and Systems
The University of Texas at Austin
Austin, TX 78712
[email protected]
Abstract
The presence of software systems within the manufacturing enterpriseis significant and growing. The cost and complexity of softwarecomponents must be controlled to maintain competitive operations.SEPA is a design methodology that creates traceable, comprehensible,and extensible component-based system design specifications based onrequirements from system clients and domain experts. Through theapplication of Artificial Intelligence techniques, the SEPA tool suitepresents itself as a unique tool offering among software developmenttools.
1. Motivation
The presence of software systems within themanufacturing enterprise is significant and growing.Software is integral to factory floor operations: from
inventory management systems, production planning andscheduling systems to shop and machine control.
According to Gary Gettel, Director of Factory Integrationat Sematech, software continues to play an ever-increasingrole in manufacturing:
Software content in equipment is growing by morethan 25% per year. To prevent this increasedamount of software complexity from derailingeffective factory operation, more reliable,predictable fail-safe software will be required.Higher utilization of commercial software subsystems,greater maturity of the industry’ssoftware development capability and reducedsoftware customization through more configurablearchitectures will be needed. (Gettel 1998)
The cost of installing and customizing commercial-offthe-shelf (COTS) software, developing in-house softwaresystems, and integrating new software systems withexisting systems can be enormous. In semiconductormanufacturing, for example, the cost of integration is often3-10 times the basic cost of the manufacturing systemproduct (Weber 1998).
The difficulty achieving manufacturing componentintegration is influenced by a number of factors, includingever-increasing process/factory complexity and the
Copyright © 1998, American Association for Artificial Intelligence
(www.aaai.org). All rights reserved.interaction of multiple perspectives (e.g. technology,business, personal) (Weber 1998). Furthermore, it isdeceptively easy to underestimate the cost of softwaremaintenance when planning a software budget. An oftencited study by Schach places maintenance at 67% of totallifecycle costs, while the requirements and specificationphases account for only 7% (Schach 1990). The premiseof the research described in this paper is: Investment in
formal, repeatable requirements analysis and verificationwill reap rewards in later phases in the lifecycle,specifically reduction in maintenance costs and support forintegration of system components.#p#分页标题#e#
2. System Engineering Process ActivitiesSEPA is a design methodology that creates traceable,comprehensible, and extensible system design
specifications based on requirements from system clientsand domain experts (Barber, Graser et al. 1998). Thefunnel abstraction is chosen (see Figure 1) to represent a
spectrum of user inputs/requirements that are narrowed,refined, and structured into a system design.
As with many domains, software developers andintegrators in the manufacturing domain aim to address anumber of commonly recognized software engineeringissues, including changing requirements, communicationamong stakeholders, adaptable architectures, andintegration of COTS solutions. The SEPA methodologyand tool suite focus on supporting such goals by providing:
1. defined deliverables to improve communicationamong stakeholders;
2. the use of multiple views on a variety of graphicalknowledge models developed directly from knowledgeacquisition;
3. a process for merging the knowledge modelsresulting from different domain experts yielding a unifiedset of user requirements;
4. a method for distinguishing between requirementsrelating to a specific system implementation and thoserelating to general domain knowledge;
5. support for requirements changes duringdevelopment;
6. the designation of adaptable domain componentsbased on responsibilities for services and tasks. Theresulting reference architecture represents the domainindependent of implementation, allowing it to be used for afamily of applications in the domain;
7. traceability and verification throughout the analysis
Methodology范文-dissertation Methodology范例and design process; and
8. early detection of component integration issues
through a domain-based reference architecture
representation that includes integration rules describing the
constraints and dependencies between components.
The SEPA methodology emphasizes the separation of
user requirements for a particular application from the
knowledge applicable to the general domain. Whether
elicited simultaneously or independently, an application
cannot be created without gathering information about the
domain as a whole along with the requirements of the
specific application.
During Knowledge Modeling, Knowledge Engineers
employ “knowledge models” (e.g., message sequence
charts, task descriptions, etc.) to graphically depict and
document knowledge acquired from domain experts and
promote verification and validation feedback cycles. A
single KA session may result in several new KMs.
The Domain Model (DM) is a unified homogenous
model. The representation for the DM contains more
information than can be viewed at any one time, resulting
in multiple views. These views are often graphical and
usually extract relevant model details. During the KM and
DM stages, the knowledge engineer repetitively refines and#p#分页标题#e#
structures the domain information.
Concurrent with the extraction of domain requirements
during Domain Model development, the Knowledge
Engineer (KE) also extracts application requirements to
populate the Application Requirements Model (ARM).
During the KA process, Knowledge Engineers (KE) are
typically presented with two distinct types of information
from the Domain Expert (DE): the domain-specific and the
application-specific. In an ideal situation, the knowledge
engineer would have separate KA sessions with the domain
expert for each of these types of information. However,
the domain expert does not typically have this abstracted
view of his work and may find it difficult to provide
information to the KE in this manner. The preferred
approach for SEPA is to let the domain expert provide a
complete “data dump” of information, whether it relates to
the entire domain, current project, or past projects. This
information is captured in Knowledge Models, which
necessarily contain both domain-specific and applicationspecific
information. The translation from the Knowledge
Models to the Domain Model only preserves the domainspecific
information.
A Reference Architecture (RA) is a repository of
domain components reusable in a “family” of domain
applications. A component is an object-oriented class
consisting of (1) attributes and services, (2) behavior, and
(3) the set of constraints and dependencies between itself
and other components. A single component may be
realized by one or more actual objects (or components)
during implementation.
The SEPA reference architecture must be completely
domain-specific and be highly flexible for building similar
systems in the future. This flexibility is achieved because
the components are described in terms of “what” they do,
which is less dynamic over time compared to “how” they
do it. As a result, these component definitions can outlive
technology solutions that were available during the
analysis and design activities.
The requirements are originally captured in knowledge
models, which are then translated into Application
Requirement Templates (ARTs). An ART details the
application requirements in terms of classification, source,
target, and intention. Before the application requirements
are applied to the RA, they are first translated into the
Component Application Requirements Model (CARM)
which describes these requirements in the “component
language” of the RA.
Technology Brokering (TB) constructs a System
Design Specification by mapping between available
technology solutions and RA components. Knowledge in
the CARM and relationships to the RA components guide
decisions in selecting “how” a domain service in the RA#p#分页标题#e#
can be satisfied by technology solutions in a particular
application. The solutions are chosen based on any
number of design trade-off concerns (e.g. cost, availability,
ease of implementation, etc.).
3. SEPA Tools
The following section outlines the tool suite designed to
support the SEPA methodology. Gathering, managing and
refining knowledge is a significant part of the total effort in
the development of large, complex software systems.
While tool support cannot fully replace decisions and
contributions provided by system clients, users, integrators,
and developers; it can assist personnel in managing the
large quantity of information associated with a
development effort. Furthermore, tool support can guide
personnel in maintaining traceability, documenting
rationale for decisions, identifying inconsistencies, and
applying evaluation metrics. Figure 2 shows the SEPA
tool suite overlaid on the SEPA activities funnel.
Subsection 3.1 briefly outlines the implementation
approach used by each tool Subsections 3.2 through 3.5
describe the SEPA suite tools and hi-light the knowledge
representations and AI techniques they employ.
Creation of
Reference Architecture (RA)
Creation of
Domain Model (DM)
Creation of
Knowledge Models (KM)
Knowledge
Acquisition (KA)
Creation of
Application Requirements
Model (ARM)
Creation of
Component Application
Requirements Model (CARM)
Technology Brokering (TB)
User
Inputs/requirements
System Design Specfication
Figure 1: Systems Engineering Process
Activities Funnel
3.1. SEPA Tool Implementation Approach
To support such runtime objectives as third party tool
interoperability and access by many users in large
development projects, the SEPA tool suite implementation
uses a CORBA backbone accessible via web-based clients.
Figure 3 presents a high-level view of general
implementation approach followed by each of the SEPA
tools. Included in the architecture are an interface client
process (implemented in Java and accessed through a web
browser), a set of SEPA backend services with persistent
storage, and a LISP-based reasoning service. The
processes run on separate platforms communicating via
CORBA. Interface Definition Language (IDL)
descriptions of SEPA tools assist in incorporating thirdparty
tool interactions. (Orfali, Harkey, Edwards. 1998)
Browser-based
Java
CLIENT
Procedural
SEPA Services
Reasoning
Services (LISP)
CORBA
Figure 3 - SEPA Tool Architecture
3.2. Hybrid Domain Representation Archive
(HyDRA)
The Hybrid Domain Representation Archive (HyDRA)
focuses on knowledge modeling and the translation of the
Knowledge Models (KMs) to the Domain Model (DM).#p#分页标题#e#
HyDRA’s objectives are to:
·aid the knowledge engineer by providing tool support
for knowledge acquisition and modeling. The tool
includes document management functions (e.g.
versioning, access control, change logs, etc.) in addition
to intelligent reasoning functions to guide the user in
model creation and unification.
·automate the transition from unstructured, incomplete
requirements to formal, complete, and consistent
requirements.
The following section provides an overview of the
HyDRA tool and is followed by a more detailed look at
HyDRA’s knowledge representation issues.
3.2.1 HyDRA tool overview
The benefits of formal requirements to designers are
unquestionable. However, clients are not likely to know a
formal specification language. The “requirements gap”
that ensues typically results in implementation and
maintenance cost overruns, rework, and delay. HyDRA
provides a semi-automated facility for iterative
requirements refinement. The translation process used in
requirement refinement identifies inconsistencies and
incompleteness in the KMs. The process continues by
abstracting away the application requirements and
synthesizing the KMs into a complete, consistent DM. It
further helps to document rationale for KM and DM
creation as well as to evaluate propagation effects of
changes on requirements in the future.
During translation, the user guides the application of
heuristic rules and corrects default rules where needed.
Rule applications and user corrections are cached for
documentation and future re-application of the translation
process. Traceability is preserved across the translation and
assists in the definition and validation of requirements
from multiple knowledge sources. HyDRA provides “back
verification” of modifications to the Domain Model against
the original Knowledge Models and records decisions
where the KE wishes the requirements captured in the
Domain Model to deviate from information in a
Knowledge Model.
The examples shown in Figures 4 and 5 show a portion
of two knowledge models that HyDRA could merge.
These knowledge models are representative of those that
would be derived from knowledge acquisition with experts
from an electro-mechanical assembly plant. When HyDRA
attempts to merge these representations, it will detect the
inconsistency between the process orderings (i.e., is "Resin
Encapsulation" before or after the creation of sub-assembly
6. HyDRA asks the user how to resolve the inconsistency
and records this decision as a "rationale at issue" point.
LRU
Mat.
Store
Sub-assy
5
Sub-assy
6
Sub-assy
4
Resin#p#分页标题#e#
Encapsulation
Major
Assy 7
Major
Assy 9
Figure 4 - Portion of an example Materials
Flow Knowledge Model
Figure 2. SEPA Tool Suite
Assemble of LRU component
Create Major
Assy 9
Create Major
Assy 10
Create Major
Assy 7
Create Sub
Assy 4
Create Sub
Assy 6
Resin
Encapsulation
Create Sub
Assy 5
Figure 5 - Portion of an example Assembly
Task Hierarchy Knowledge Model
3.2.2 HyDRA Knowledge Representation Issues
Design of the HyDRA’s knowledge representations
focused on enabling the features identified in Section 2.
This section details how the SEPA methodology features
impact HyDRA’s knowledge representations.
First, to support communication among system
development participants, HyDRA has well defined
deliverables. Since HyDRA has been implemented in a
CORBA client/server architecture, the objects that together
makeup HyDRA’s knowledge representation necessarily
have their interface defined in the Interface Definition
Language (IDL). IDL definitions for the knowledge
representations ease the interaction of automated tools by
decoupling the implementation details of each tool
component from the other tool components and other tools
(e.g., current SEPA tool suite development involves both
Java and LISP components).
One of SEPA’s main tenets is the emphasis on an
extended requirements gathering and analysis phase. The
implementation responsibility for this tenet rests more so
on HyDRA than other SEPA suite tools. When
transitioning from KA transcripts to KMs, the KM
notations used to describe basic concepts must be similar
to the notations used for those concepts in the KA
transcripts. The similarity in notations lessens the
possibility for errors as knowledge engineers, who lack
experience in the domain, attempt to translate the
notations. Therefore, a wide variety of graphical notations
is required and the set of required notations changes as the
project progresses. That is, representations with higher
fidelity are required to capture the fine details that are
uncovered late in the requirements gathering process.
Until recently, no clear standard “family” of graphical
notations was agreed upon. With the proliferation of
object-oriented methodologies, several more complete
notations exist for describing systems but they assume an
underlying object-oriented semantics. The Unified
Modeling Language (UML) [Rational, 1997 #121] is the
most successful example of such a notation.
Unfortunately, no corresponding standard exists for
representing information at a point when objects have not
yet been identified. HyDRA incorporates several of the#p#分页标题#e#
independent notations associated with non-object-oriented
methodologies (e.g., task hierarchies, data flows). In
addition, HyDRA leverages the popularity of the UML by
borrowing its notations where possible, yet remaining
cognizant of the fact that UML-defined semantics are often
object-based. For instance, as long as the activity diagrams
are drawn without swimlanes, they are sufficiently nonobject-
oriented to be useful as a notation in HyDRA. Just
as with the UML, HyDRA’s multiple representations allow
for an extended analysis that progresses through stages
with different representational needs.1
Another difficulty faced in borrowing from standardized
notations is over-formalization. That is, the formalism of
graphical notations, such as it is, is still too constrictive
when representing early analysis information that is
plagued with inconsistencies and incompleteness. The
analysis can not be completed instantaneously, but delay
between knowledge acquisition and the modeling of the
elicited information threatens validity. The evolution of
requirements occurs on every development effort and
contributes to cost overruns and delays. Therefore, the
SEPA methodology and HyDRA have been designed to
encourage the capture of incomplete and inconsistent
information till such a time when these problems can be
resolved. Specifically, HyDRA relaxes the syntax of the
notations, increases the expressiveness of the individual
notations, and provides a means of checking syntax and
semantics when the appropriate level of detail is available.
These changes in the notations often require the
underlying representation to be specialized. In the case of
the UML activity diagram, the notation retains its
similarities to the standard but the underlying
representation is quite different. Heterogeneous
representations are problematic when the information
contained in the various representations is inconsistent.
This case occurs often in requirements analysis because the
requirements are gathered from a diverse set of users.
Each of these users may have a different set of
terminology, a different level of abstraction, and possibly
different processes for accomplishing the same tasks.
HyDRA’s main research contribution is the merging of
heterogeneous representations with possibly inconsistent
information into a single representation that contains a
unified, consistent model of the domain. The unified
representation has more restrictions on syntax and more
formality than the individual knowledge model
representations. The translation process is a semiautomated,
iterative application of heuristic rules that is
guided by the knowledge engineer. During the translation
process, the knowledge engineer may be asked to help in#p#分页标题#e#
the resolution of inconsistencies.
In accordance with the SEPA methodology, all of the
SEPA tools maintain the ability to trace artifacts back
through the process used to derive them. HyDRA
establishes the base of this chain by maintaining links from
each model back to the knowledge acquisition where the
information was originally elicited and the domain expert
who stated the requirement. This necessitates the inclusion
of these links on each model and the creation of new links
when new models are synthesized or derived from existing
models. Furthermore, since SEPA’s open architecture may
1 The modular architecture for representations has the added benefit of
allowing HyDRA to be applicable to a variety of domains with varying
special representational needs (e.g. representations with support for
advanced geometric reasoning for manufacturing).
involve third-party tools, this link mechanism must include
a stable, external reference that can be used to refer to the
target at any later date. Careful management of this
external link is required when versioning is also
incorporated.
While verification is most often thought of in terms of
implementation compliance, the SEPA methodology
applies some form of verification to every activity. In the
analysis phase, formal verification of compliance testing is
not realistic given the form and completeness of the
information. Instead, SEPA encourages the return of each
knowledge acquisition transcript and early knowledge
model back to the associated domain expert for approval.
This feedback gives the domain expert an opportunity to
rethink his or her answers and correct misunderstandings.
The HyDRA tool assists in this process by maintaining this
verification information as a series of changes and digital
signatures indicating domain expert signoff. The state of
each model proceeds through a cycle (i.e., new, verified,
modified, reverified, … ).
Models that represent information gathered from
multiple domain experts present a unique verification
problem. It may be impossible for any one expert to verify
the entire model due to his or her limited perspective and
level of abstraction. On the other hand, allowing each
expert to verify a portion of a model can lead to models
that are only partially verified or models that are
completely piecewise verified yet still do not form a valid
whole. HyDRA’s approach is to couple the verification of
single-expert knowledge models with strict traceability
links to provide a degree of verification on models derived
through the synthesis process. As mentioned above, the
synthesis process may require additional input from the
knowledge engineer to resolve inconsistencies. This input
is recorded as a “rationale at issue” point and included as#p#分页标题#e#
part of the verification for the derived model.
Future work will expand HyDRA's reasoning
capabilities and address project progress estimations
through statistical analysis on the current set of models.
Metrics may include the amount of model integrated in
unified representations, the amount of flux in models, the
number of syntax errors, the average age of verified
models, etc.
3.3. Reference Architecture Representation
Environment (RARE)
The Reference Architecture Representation Environment
(RARE) guides the transition from the functional DM
generated by HyDRA to a component-based Reference
Architecture (RA). RARE provides support for capturing
decision rationale and tracing RA components back to
elements of the DM. To measure RA quality, RARE uses
domain independent metrics quantifying the achievement
of domain design principles.
3.3.1 Representing Reference Architecture Components
The manufacturing domain requires a modular, adaptive
software architecture that can both accommodate new
technologies as they become available and accurately
capture domain knowledge. Thus, the architecture’s
representation must strike a balance between the detail
required to describe manufacturing processes and the
degree of abstraction required for technology
independence.
A modular software architecture can be based on either
functional or object-oriented components. Objectoriented
(OO) knowledge representations, particularly
focused on extensibility and reuse are typical desirable
qualities in a modular Reference Architecture. OO
approaches define classes which present interfaces
describing “what” the class can provide, hiding the
implementation details.
RARE assigns responsibilities to components based on
domain tasks. Task resources (or service dependencies)
determine the data (or services) required (or provided) by
a component. For example, for a Car component to
provide a Drive service, it requires the DeliverFuel service
provided by a Carburetor component. A component’s
behavior is defined by the services it provides.
To represent this information, components in the RARE
Reference Architecture are represented by three categories
of information (Graser 1996):
Declarative Model (DM) - defines the attributes
contained and the services offered by a component.
Behavioral Model (BM) - defines the states of a
component, the transitions between those states, and the
events which affect transitions.
Integration Model (IM) - defines the constraints and
dependencies between components described by rules of
composition.
Components in a domain are assigned individual
responsibilities and, through mutual cooperation, achieve
system goals that satisfy domain requirements. This type#p#分页标题#e#
of cooperation leads to dependencies between
components. The integration model represents these
dependencies, categorizing them as either “static” or
“dynamic.” Static dependencies define a
consumer/supplier relationship between components.
Dynamic dependencies are rules that restrict the set of
Search
Attempt
Interim
Versions
“Search
Path”
“Search
Space”
Initial Empty RA
(No domain
coverage)
New Optimal RA
Version
(complete domain
coverage)
Increasing
Domain
Coverage
Figure 6 - Reference Architecture "Search
Space"
allowable configurations in which a component instance
can participate. For example, for a Car component to
deliver a specified power, it requires a Carburetor
component able to DeliverFuel at some minimum rate.
While all Carburetor components provide this service, the
ability to deliver fuel at the needed rate depends on the
specific Carburetor instance. These rules are used by
RIVT (See Section 3.5) during application design.
3.3.2 “Searching” for a Satisfactory Reference
Architecture
Given the set of all possible architectures that fulfill the
requirements represented in the Domain Model, there may
exist many viable architectures. There is often no single
“right” architecture. RARE approaches the Reference
Architecture creation process from the following
perspective – given a prioritized set of qualities desired in
the Reference Architecture, there is a near optimal
Reference Architecture to be "found." Figure 6
characterizes the Reference Architecture derivation
“search space.” The search begins with a complete
Domain Model and a “null” Reference Architecture. The
depth of the search space represents the degree to which
the Reference Architecture covers the information
represented in the Domain Model (i.e. completeness, to
the extent the Domain Model accurately represents the
domain). The breadth of the search space represents the
multitude of structuring and abstraction options (e.g.,
concepts X and Y could be abstracted into component A
or defined directly as components X and Y) available to
the architect given a particular set of desired qualities and
domain information from the Domain Model. The end
objectives are to sufficiently cover domain information
and to satisfy the quality goals set forth by the architect
(Barber, Graser et al. 1998).
As is typical with many applications involving search,
the traversal of a branch in a search path may need to be
abandoned if it produces unsatisfactory results; pruning
branches and reducing the search space mitigate this#p#分页标题#e#
problem and backtrack if necessary.
To navigate the search space shown in Figure 6, RARE
systematically employs the following concepts: (i) Goals:
High-level qualities determined by the architect to be
important for the RA to exhibit in this domain, such as
extensibility, comprehensibility, and maintainability; (ii)
Heuristics: "Rules of thumb" compiled from expert
experience on past projects which assist the architect in
making rational decisions in defining RA components; and
(iii) Metrics: Measurements of particular RA
characteristics that indicate whether the architect adhered
to respective heuristics.
3.4. Tool for Application Requirements
Extraction and Technology Specification
(TARETS)
The Tool for Application Requirements Extraction and
Technology Specification (TARETS) extracts the
application-specific data from the knowledge models for
use in the design of the RA and the implementation of a
System Design Specification. This extraction process is
guided by a set of heuristics that help requirements
engineers locate the application requirements within the
knowledge models. Once identified, TARETS uses that
information to populate an Application Requirements
Template (ART). Each ART is an atomic element,
describing a single application requirement, and divided
into four major sections:
Type - a hierarchical classification of the requirement,
Sources - who or what generated the requirement,
Targets - model elements impacted by this requirement,
and
Intention - justification and other descriptive
information.
The Sources and Targets sections refer to elements
found in the Knowledge Model via “semantic links”. As a
result, a key responsibility of TARETS during the Creation
of the Application Requirements Model (ARM) is to
monitor the evolution of the Knowledge Models as they
are synthesized into the Domain Model to keep the links
valid. For the user, this means that as concepts, tasks, and
other model elements are being merged, modified, and
renamed by HyDRA, the domain terminology used to
describe the application requirements will be updated
accordingly.
This monitoring and updating process also occurs during
the Creation of the Component Application Requirements
Model (CARM), due to the analogous process of building
the Reference Architecture from the information found in
the Domain Model. Describing the application
requirements from a component perspective is necessary
for RIVT to index the CARM and insure technology
instances satisfy appropriate application requirements.
3.5. Requirements Integration and Verification
Tool (RIVT)
The components defined in the SEPA Reference
Architecture are domain-based – that is, they are designed#p#分页标题#e#
to be technology independent. RIVT aids the developer in
realizing system designs by performing Technology
Brokering based on application requirements from
TARETS and domain requirements represented in RARE
components. This entails matching RA components to
available technologies, insuring that those technologies
satisfy the application requirements, and integrating those
technologies into a complete system configuration.
Technology Brokering produces a System Design
Specification that describes the chosen technology
solutions and how they inter-operate to satisfy the
requirements of the system. If RIVT is unable to locate a
satisfactory technology solution during the brokering
process, the tool can generate a “notional” component.
After the System Design Specification is approved, the
specification of this notional component can be exported
and sent to technology providers as a “Request To Build”.
As component instances are selected from the repository
and configured to form a System Design Specification,
RIVT’s integration engine ensures interdependency
requirements (represented in RARE’s component
Integration Model) are not violated. Furthermore, the set
of interdependency rules fired, messages issued, and
evaluation results are captured in a log. The log then
serves as a rationale to support the System Design
Specification.
4. Conclusion
The Systems Engineering Processing Activities (SEPA)
methodology being developed at the University of Texas at
Austin in the Laboratory for Intelligent Processes and
Systems (LIPS) seeks to improve the systems engineering
process by providing of a comprehensive, object-oriented
development methodology and a suite of supporting tools.
Today’s manufacturing systems are critically dependent on
the development and maintenance of software systems,
including installing and customizing COTS solutions as
well as developing in-house solutions. For this reason, the
control of software development and maintenance costs has
a direct impact on the control of manufacturing process
costs.
An overall emphasis of the SEPA methodology is to
provide a domain-based approach that expands reuse by
enabling the development of multiple applications from a
single domain analysis effort. SEPA also assists in the
communication between client and developer during the
requirements gathering process.
Recognizing that many modeling methodologies do not
adequately support early analysis efforts, SEPA
emphasizes earlier activities to provide a sound foundation
for component derivation, reuse, and integration. Issues
inherent to software development for manufacturing and
SEPA’s approach for addressing them include:#p#分页标题#e#
· Managing requirements in a complex domain:
SEPA aids in managing complex domain and
system requirements throughout the development
process. Traceability is an integral part of the
SEPA tool suite, linking requirements as they
evolve from their original informal representation to
a structured, component-based representation.
· Multiple perspectives: HyDRA’s knowledge
representation scheme supports multiple domain
perspectives and guides the knowledge engineer in
resolving these perspectives into a synthesized
Domain Model.
· Knowledge capture in an increasingly advancing
domain: The increase and refinement of domain
knowledge is inevitable, and a considerable amount
of effort is spent merging this information into
existing knowledge. The knowledge representation
schemes in HyDRA and subsequent SEPA tools are
designed to support the capture and evolution of
requirements over time. HyDRA assists in merging
new or additional information into existing domain
knowledge and SEPA’s traceability features allow
this information to be reflected in Reference
Architecture components and system designs.
· Higher utilization of components and sub-systems:
RIVT aids the developer in realizing system designs
by performing Technology Brokering based on
application (system) requirements from TARETS
and domain requirements represented in RARE
components. Greater component reuse is achieved
because requirements for a specific system are
represented separately from requirements inherent
to the domain. Furthermore, components are
represented in a technology-independent manner,
allowing their definition to endure changes in
technology.
· Reduced customization through more configurable
architectures: Based on user-established
architecture goals. RARE assists the system
architect in transitioning from a functional-based
Domain Model to a component-based Reference
Architecture.
· Integrating COTS systems: RIVT allows the
designer to compare system design options using
commercial technologies registered as instantiations
of domain components. Furthermore, because
SEPA Reference Architecture components are
represented independent of implementation,
commercial technologies can be registered as
instantiations of domain components without
modifying the Reference Architecture.
Through the comprehensive application of Software
Engineering methods and Artificial Intelligence
techniques, the SEPA tool suite presents itself as a
unique tool offering among software development tools.
Furthermore, it supports the needs of the manufacturing
domain by providing a more mature software
development capability.#p#分页标题#e#
5. References
Barber, K. S., T. J. Graser, et al. (1998). The Systems
Engineering Process Activities: The Methodology and
Supporting Tools. Austin, TX, The University of Texas at
Austin.
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