movement or reorganization of database systems,
application programs and program interfaces”.
In general, the motivation for any migration
process is the incremental transition from an initial
organisational situation A, which is unsatisfactory in
some aspect, to a desired situation B where the
problem is addressed. Possible causes to such
change include perceived opportunities, threats,
social pressures or political decisions, including for
example the opportunities offered by new
technologies, increased customer demand for better
service quality or the globalisation of markets. The
main objective of our approach is the provision of a
semantic roadmap based on a set of Knowledge
States that define a migration process. We approach
migration not as an undirected process, but as a
purposive activity driven by organisational goals.
Hence, its effectiveness depends on being able to
make good decisions about what migration goals to
pursue, on selecting the appropriate strategies for
achieving the desired goals, and on guiding the
application of the chosen strategies. In order to be
able to systematically plan and model a legacy
migration process, a series of relevant procedures
are executed. It is possible to make the distinction
between six different types of Knowledge States
involved in a migration process, namely:
i) Knowledge about the current business
processes, the legacy systems that serve these
processes, as well as the requirements for migration
(As-Is).
ii) Knowledge about the stakeholders’ goals and
how they can be satisfied in terms of alternative
migration plans as well as the specific processes that
will achieve the predefined migration goals (Migrate
Goal Model – Migrate Process Model).
iii) Knowledge about a set of proposed migration
transformations that describe a unique way of
pursuing stakeholders’ goals (Migration Scenarios).
iv) Knowledge about the validity of the above
transformations and thus, knowledge about the most
suitable proposed plan (Candidate Migrate
Scenario).
v) Knowledge about the candidate legacy
systems that are to be migrated (Legacy Systems).
vi) Knowledge about the most suitable custom or
off-the-self migration solution based on the profile
of the legacy systems (System Migration).
Two additional states in the framework are
available: the Null State and the Target State. These
describe respectively the state where ‘no knowledge’
about the migration is available and the state where
‘enough knowledge’ has been obtained.
The “Migrate Method” extends across the three
different views or levels of abstraction, which
feature in enterprise modeling. It examines a
migration process from the intentional, operational
and informational perspective. The intentional view
is concerned with the enterprise objectives and the
reasons that prescribe these objectives. It also
considers the actors and the corresponding roles that
they play in the organisation as well as the business
rules. The operational view concerns the business
process level, describing the logical localization of
data in the different departments of the enterprise,
the distribution of functions in these departments
and the actors involved in each function. Finally, the
informational view defines the logical and physical
components of the information systems that support
the business processes. The “Migrate Method”
encompasses all three profiles and integrates the
three complementary views as submodels.
Knowledge States and submodels form the “Migrate
Method” Metamodel (figure 1) that defines the
logical form of the migration process. The
metamodel includes information about the semantics
of legacy migration; it identifies the entities, their
attributes and the explicit relationships between
them. The following paragraphs provide a
description of the three submodels.
With reference to figure 1, a
Migration Goal is a
desired state concerning a legacy system that needs
to be attained. Migration Goals pertain to
stakeholders. A stakeholder is defined as someone
who has an interest in the system design and usage.
Migration Goals are generated by issues. An issue is
a statement of a Strength, Weakness, Opportunity or
Threat that leads to the formation of the goal.
Migration Goals are then realized by Migration
Processes. This is expressed in the metamodel
through the Goal Realisation Relationship. Note that
the Migration Goals cannot be mapped directly onto
Migration Processes.
The transition process from intentions to
processes and thus from the intentional to
operational profile of the migration process,
encompasses the ‘causal transformations’ of general
migration goals into one or more sub-goals that
constitute the means for achieving desired ends.
Each step can result in the identification of new
goals that are linked to the original one through
causal relations, thus forming a hierarchy of goals.
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