=Paper=
{{Paper
|id=Vol-263/paper-9
|storemode=property
|title=Systematic Construction of Goal-Oriented COTS Taxonomies
|pdfUrl=https://ceur-ws.org/Vol-263/paper9.pdf
|volume=Vol-263
|dblpUrl=https://dblp.org/rec/conf/caise/Ayala06
}}
==Systematic Construction of Goal-Oriented COTS Taxonomies==
https://ceur-ws.org/Vol-263/paper9.pdf
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Systematic Construction of Goal-Oriented COTS
Taxonomies
Claudia Ayala
Technical University of Catalunya
Campus Nord 08034, Barcelona, Spain
cayala@lsi.upc.edu
Abstract. The use of Commercial Off-The-Shelf (COTS) components is be-
coming a strategic need because they offer the possibility to build systems at
reduced costs and within shorter development time. Having efficient and reli-
able COTS components selection methods is a key issue not only for exploiting
the potential benefits of this technology, but also for facing the problems and
risks involved. Searching COTS components requires overcoming several ob-
stacles: the growing size and evolvability of the COTS marketplace, the de-
pendencies from the components to be selected with others, and the type of de-
scriptions currently available for those components. The main goal of this thesis
is to provide support for a reliable and comprehensive structuring of a reuse in-
frastructure for the COTS components marketplace. With this aim, we propose
a method for the construction and maintenance of goal-oriented COTS taxono-
mies based on a solid domain analysis; guiding the gathering of sources of in-
formation, modeling requirements and dependency relationship among do-
mains, and organizing knowledge in any segment of the COTS marketplace.
1. Introduction
The use of COTS components for building systems is becoming a strategic need in a
wide variety of application areas. In general, COTS are software components that
provide a specific functionality, available in the market to be purchased, interfaced,
and integrated into other software systems [1]. The potential benefits of this technol-
ogy are mainly its reduced costs and shorter development time, while maintaining the
quality. Nevertheless, many challenges must be faced for adapting the traditional
software engineering activities in order to exploit these benefits [2].
One of the most critical activities in COTS-based development is the selection of
the components that must be integrated therein. Selection is basically composed of
two main activities, namely searching of candidates and their evaluation with respect
to system requirements. However, while many approaches exist for driving evaluation
[3] (e.g. CAP, CARE, CEP, CRE, OTSO, PECA, PORE, QESTA, STACE, and Story-
board), it is not the case of the searching phase, making the selection process expen-
sive and inefficient. This lack of proposals is a serious drawback that impacts in selec-
tion reliability: no matter how good is the evaluation process, selection may be wrong
if the candidates chosen to be evaluated are not the right ones.
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2. Problem Statement
One of the essential problems in reusing software components is locating and retriev-
ing them from a large collection [4]. COTS are a special class of reusable compo-
nents, this gives raise to a new problem: how to structure the knowledge about this
COTS marketplace and in particular how to know which types of COTS are available
and their objectives in such a way that searching the marketplace becomes a feasible
task? Furthermore, COTS search must cope with some critical characteristics:
1. The growing size of the marketplace: New and improved products and technologies
are continuously offered.
2. The rapid changes in the marketplace: New versions of existing products are re-
leased every few months and many times they offer services that initially were seen
as belonging to different segments (e.g. current mail servers systems usually pro-
vide instant messaging facilities)
3. Dependencies among COTS: COTS are not designed to operate isolated [5], but in
collaboration with others, which results in many dependencies among them.
4. Type of descriptions available for COTS: COTS suppliers do not provide the kind
of structured information that would allow performing automated or at least as-
sisted search. The situation is aggravated by the fact that they tend to highlight
strengths and hide weaknesses of the licensed components.
Consequently, when carrying out a particular searching process, some practical
questions arise: Which are the market segments of interest for this particular context?
Which are the relationships among the identified markets segments and which are
their implied needs? How can structured and trustable information be obtained for the
COTS available in the marketplace?
In this context, we claim that an effective COTS search strategy shall rely on a
thorough description of the COTS marketplace whose nature adapts to the above men-
tioned characteristics (diversity, size, evolvability, interoperability, lack of structure
and subjectivity) and therefore provides real answers to the questions above.
3. Related Work
Due to the highly applicable nature of the subject of our research, we find related
work not only concerning cientific proposals but also in the way that the COTS mar-
ketplace is really organized nowadays. Thus, profit and non-profit organizations have
defined categories of services, products, and knowledge, usually structured in a hier-
archical form. This type of organizations range from IT consultant companies such as
Gartner [6] or Forrester [7], commercial web-based companies as ComponentSource
[8], professional societies as INCOSE [9]; to the academic world in which organiza-
tions, teams and individuals have presented their own proposals that range from spe-
cific of one domain [10] to a wide range [4], [11] or even a field [12]. Moreover, it is
well-known that the effort devoted to these activities is more valuable if the attributes
can be reused; in this sense a wide range of works about COTS characterization exists
[13-16]. However, these categorization proposals present some drawbacks, mainly
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because sometimes, the meaning of a particular domain is not clear without further
examining the items, especially if the domain is absolutely unknown to the user. Con-
sequently the understanding, use, evolution, extension, and customization of the cate-
gorization proposal may be difficult. In [17] a survey of different approaches is given
and also emphasizes some of these problems.
On the other hand, some proposals have arised for finding and identifying COTS
components, such as [18], [19] and [20] which propose the use of automatic or semi-
automatic search engines to identify COTS information in the web relying on compo-
nent catalogues supplied by related companies. However, besides the mentioned prob-
lems of these kinds of catalogues, though these approaches achieve a high level of
efficiency and low cost, they do no achieve the same level of accuracy and reliability
of the acquired information as manual approaches, increasing many risks involved in
COTS selection. Therefore, as other recent studies have concluded [21], we claim that
there is a gap among COTS selection methods and their real application.
4. Proposed Solution and Research Method
For solving the stated problem we specifically propose a prescriptive goal-oriented
method for building and maintaining a reliable reuse infrastructure that may be used in
COTS search processes by arranging marketplace segments as a taxonomy. Our pro-
posal relies on a four iteration research process supported by industrial experiences
and academic cases studies we have been undertaken under action-research premises
[22], as well as literature survey and grounded theory [23].
The initial iteration departed from an industrial experience in the context of an aca-
demic record management information system development which was planned to
include some strategic business functionalities. We undertook a thorough analysis of
the domain and experimented the problems mentioned in section 2. As a result, we
studied the state of the art and evaluated the applicability of suitable methodologies
for handling the problem, as related in [24].
In the second iteration, we consolidated previous results, proposing the use of goal-
oriented approaches as a basement of our solution. A goal is an objective that should
be achieved and may be formulated at different levels of abstraction [25]. We found
that goal characteristics are helpful to build abstract, well-founded, and stable tax-
onomies capable of dealing with the rapid evolution of the COTS market and manage
all the information related in a COTS selection process [26]. Subsequently, perform-
ing some formative case studies related with Requirements Engineering Tools, Soft-
ware Application Development Tools and some sub-categories of Enterprise Applica-
tions (with emphasis with those related to Content Management), a preliminary ver-
sion of our method called GBTCM (Goal-Based Taxonomy Construction Method)
[27] was proposed; it was inspired by GBRAM (Goal-Based Requirements Analysis
Method) [28] (a widely recognized methodology in the context of Requirements Engi-
neering) as a framework for integrating the goal-oriented mechanisms and techniques
needed for formalizing the construction of taxonomies from goals. In this stage, also
the goal-modeling dependencies strategies were studied [29], adapted, and included in
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the method [30]. The third iteration was focused on deeper analysis and preliminary
validation of the results obtained in the previous one by means of the cases related
with the Real-Time Synchronous Communication and Message-based Communication
Systems, identifying and overcoming some method design flaws, resulting in an im-
proved version of our preliminary method, called GOThIC (Goal-Oriented Taxonomy
and reuse Infrastructure Construction) [31].
The ongoing last iteration aims at achieving the complete validation of our ap-
proach, its tool implementation, and thesis writing.
Summarizing, our GOThIC method consist in 7 high-level activities stated as:
1. Exploration of information sources: This activity must be able to locate as much
relevant information as possible, dealing with the diversity of its type, supporting
media, cost, etc., by means of a knowledge acquisition program which allows ex-
tracting knowledge from the domain by reconciling the characteristics of the avail-
able sources with those of the taxonomy construction process.
2. COTS marketplace domain analysis. Its goal is to identify the basic elements of
the domain from the information sources obtained previously, organize an under-
standing of relationships among these elements, and represent this understanding in
a useful way.
3. Identification, refinement, and statement of goals. These activities are iterative
and have the next objectives: Identification aims at extracting goals from available
sources applying different goal-acquisition techniques. Refinement entails the goal
refinement considering obstacles, scenarios to uncover hidden goals and mecha-
nisms to discover synonymous or duplicated goals. Statement consists on express-
ing the goals in a systematic way. We use a pre/post style for specifying these
goals, i.e. stating which conditions are met when others hold.
4. Establishment of dependencies. We have identified that a COTS component may
need another for: enabling its functionality (e.g. in order to follow document life-
cycles, document management tools need workflow technology to define them);
complementing its functionality with an additional feature, not originally intended
to be part of its suitability (e.g. a web page editing tool can complement a web
browser for editing web pages); enhancing its quality attributes (e.g. resource utili-
zation can be improved significantly using compression tools). Relationships are
gradually identified analyzing the goal information obtained in previous activities.
These relationships are declared as dependencies using goal-oriented models, spe-
cifically i* models [32].
5. Goal-taxonomy structuring. The organization of goals comes from the analysis of
pre and postconditions stated for each goal. Goals are operationalized in terms of
variables which, in the case of categories, represent classifiers (e.g., number of
users of the system, data processing profile, …). These classifiers may take values
(e.g., for data processing profile, values are Acquisition, Storage, Preparation,
Analysis), and for each possible value, a subcategory or market segment applies.
Thus, Goals are defined over a set X ={xk}n of independent variables that
characterize the taxonomy. Goal satisfaction is defined by means of assignment to
the variables, thus for each assignment ass =(x1←v1, …, xn←vn), the expression
satass(G) yields true if the goal G evaluates to true for this assignment, otherwise
false.
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6. Taxonomy validation. In order to be useful for driving COTS search processes,
we require three conditions to the taxonomy: to be consistent, to be complete and to
be not ambiguous. Using decision trees properties we defined the process of taxon-
omy validation as the repeated application of some stated transformation rules over
the nodes to manipulate the hierarchy until reaching a stop condition. We detailed
this process in [33].
7. Knowledge base management. Many studies refer that it is necessary to build a
body of knowledge towards a knowledge-based framework for COTS components
identification [21]. GOThIC provides an efficient mechanism to maintain a reposi-
tory of the obtained knowledge. UML class diagram in Fig. 1 defines the form that
this repository exhibits -see [31] for details-. This knowledge base is the infrastruc-
ture support not only for an easy evolution and maintaining of taxonomies, but also
for their suitability to specific organizational concerns.
Fig. 1. Conceptual model for goal-oriented COTS taxonomies: overview.
Although presented as sequential for clarity, the method activities may in fact be in-
tertwined and iterated as required to obtain the target infrastructure incrementally.
Furthermore, GOThIC does not depend on the extent and characteristics of the taxon-
omy built (e.g., a small part of the COTS marketplace such as photo processing soft-
ware, or a huge portion like business applications). Its ultimate goal is to populate a
knowledge base with data according to the UML conceptual model sketched in Fig. 1.
At the heart of this model lies the taxonomy composed of two types of nodes, market
segments and categories, which are characterized by their goals and their relationships
declared as dependencies. Market segments are the leaves of the taxonomy, whilst
categories serve to group related market segments and/or subcategories (e.g., the cate-
gory of communication infrastructure systems or financial packages).
From a semantic point of view, market segments stand for the basic types of COTS
components available in the marketplace (e.g., the domain of anti-virus tools or
spreadsheet applications), i.e. atomic entities covering a significant group of function-
ality such as their decomposition would yield to too fine-grained domains. As a con-
sequence, COTS components are associated with market segments and not with cate-
gories (although an indirect relationship exists, because market segments belong to
categories). Components may cover more than one market segment. For simplification
purposes, we are not distinguishing at the moment versions of components; two differ-
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ent versions are treated as two different products. Dependencies among nodes provide
a comprehensive view of the marketplace. In the case of dependencies among market
segments, they stand for interoperability needs (e.g. mail server systems depend on
anti-virus tools to support integrity). Concerning categories, more abstract relation-
ships are modeled. In addition to taxonomy nodes, dependencies may involve goals,
when the relationship can be established more accurately. The Dependable Entity
superclass allows modeling this situation comfortably. Note that dependencies are
represented by a ternary association, because they involve two elements (depender and
dependee) and the relationship itself. Finally, nodes have auxiliary artifacts bound,
which are built during the domain analysis activity. Their construction is a result of
the analysis of some information sources which are gathered, analyzed, and prioritized
according to several characteristics. Further method description, is available at [31].
5. Validation and Future Work
As we mentioned above, preliminary validation of each research stage was performed
by means of formative case studies [26],[27],[31],[33],[34]. The results are promising
from the academic point of view, therefore, our main purpose for future work is fo-
cused on industrial validation of the final proposal involving an industrial partner, by
means of some action-research collaboration, based on the principles of [35] for as-
sessing the usability and effectiveness of the GOThIC method; as well as the devel-
opment of tool support starting from the UML conceptual model sketched in Fig. 1.
6. Applicability of the Proposal
Basically it requires the following characteristics to be applicable:
• The taxonomy addresses a category of market segments that is of general interest.
This means that a great deal of organizations needs to select COTS components
from these segments (i.e. communication infrastructure, ERP systems, security-
related systems, etc); hence, the number of selection processes that take place will
be high and then reusability of the models likely to occur.
• The addressed market segments offer COTS components of coarse-grained granu-
larity. This makes domain understanding more difficult, time-consuming and cum-
bersome and therefore domain analysis and taxonomy construction are helpful.
Market segments such as CRM and ECM systems are typical examples, whilst time
or currency converters are not. Thus, having knowledge available and classifiers to
know when a market segment is of interest is a great help, especially appealing in
those selection contexts in which the organization that is interested in the selection
does not have clear requirements about the kind of system needed.
• The COTS components search activity is monitored by an organization that accu-
mulates experience from past selection processes. This organization will find valu-
able to have means to transfer knowledge from one experience to another and to as-
sist their clients in the maintenance of their COTS-based software systems.
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7. Contributions and Target Audience
Our method is aimed at face COTS components search, based on the notion of goal
for building abstract, well-founded and stable taxonomies, which may evolve as the
marketplace does. It is a way to overcome the COTS marketplace characteristics:
• Growing size of the COTS marketplace. Proliferation of information is taken into
account by prioritizing information sources in the bases of given criteria (time,
money, reliability, …). Appearance of a new market segment is easier to handle
than in other approaches, since it requires to locate its place in the taxonomy using
the defined classifiers, and once there even some useful artifacts are inherited (e.g.,
quality models and glossaries).
• Rapid changes in the COTS marketplace. We use a goal-oriented approach, in the
belief that goals are stable concepts [25]. Also, the fact that taxonomy nodes do not
stand for types of COTS components available but for related groups of functional-
ities, makes the taxonomy more robust with respect to the segment barriers move-
ment effect mentioned in the introduction.
• Dependencies among COTS components. We represent explicitly these dependen-
cies with a model built with i*, a widespread and accepted notation in some other
disciplines (e.g., requirements engineering, agent-oriented development).
• Type of descriptions available for COTS components. We have identified activities
to cope with the diversity, lack of structure and lack of reliability of information
about COTS components. Also, our resulting taxonomy provides an external view
that is: well-founded (with a clear rationale of the proposed structure), validated
(sound, complete, pair-wise disjoint and balanced) and ready to browse (using the
defined classifiers).
As a result, diverse actors may benefit from our approach: a) IT consultant compa-
nies offering assessment for business automation may structure their services better; b)
Commercial web-based companies or portals may structure their offering in well-
founded categories with a clear rationale behind; c) Medium- and large-size compa-
nies with their own IT department may be more confident on their own selection proc-
esses; d) Software engineers which usually carry out COTS components selection may
structure better their knowledge and may aim at a better return of investment.
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