Event Derivation Analysis
Objectives
The goal of this task is to define a migration path from legacy systems into
an event driven paradigm using redevelopment techniques. The approach is
premised on the need to expedite the analysis process, while concurrently
defining a migration path from legacy applications.
Event diagrams represent business process flow. An event is defined as a
"happening" in the business which influences behavior through the
recognition that a process has a cause and effect behavioral pattern. Events
depend on two key concepts: an "operation" or business process and a
"trigger" which activates an operation. Event modeling concepts are
derived from the Martin/Odell Object Oriented Analysis (OOA) model.
While current systems implicitly depend on events today, there is no clear
indication as to how events are invoked. So while an event driven approach to
modeling more accurately depicts reality, transition to this architecture is a
complex challenge. As in other TIM tasks, the goal is to streamline this
transition process by excavating legacy functions and the activities that
initiate those functions.
Finally, this task is a required prerequisite to business rule derivation.
Events dictate state transition timing, a key requirement for placing rules in
context. Bypassing this task will likely lead to an unsuccessful business rule
derivation effort. Specific objectives for event derivation analysis are listed
below.
· Develop a target event diagram based on analysis of legacy environment being transitioned to an event driven paradigm
· Abstract implied events from legacy applications to augment and cross check top-down event analysis
· Refine this model based on event driven techniques and analyst input
· Optionally synchronize event specification process with corresponding legacy system functions via the Legacy Transition Meta-model LTM
Entrance Criteria
This task, as much as any TIM task, is linked to techniques defined in
other development methods. Event modeling, in the context of this task, is based
on the Martin/Odell (OOA) model referenced earlier in the task objective
section.
This and other prerequisite entrance criteria are listed below.
· Acceptance and availability of event modeling techniques defined in the Martin/Odell model
· A corresponding object oriented, event driven development methodology that defines notations and techniques under an integrated approach
· Completion of general systems architecture assessment data flow analysis depicting on-line screen and batch job data flow (DFD) diagrams
· Completion of presentation layer assessment depicting user input/output views of an application
Note: User views, coupled with DFD analysis, provide a baseline for
extracting implied events from legacy architecture.
· Completion of function dependency modeling effort via function dependency analysis task
· Completion of current function to current program mapping via function hierarchy analysis task
Note: If following were pursued, either as TIM transformation tasks or
similar efforts, it further simplifies event excavation. These tasks, however,
tend to be mutually exclusive to the object/event driven redevelopment path.
· Optionally, completion of Inventory/Analysis process hierarchy/dependency analysis task or similar process flow analysis effort
Note: The following supports the analysis effort as well as linking event
definitions within this task to subsequent development activities. If business
rule derivation is envisioned, LTM utilization is required.
· Optional availability of populated LTM that links forms, programs, execution language and other legacy objects to functions and, optionally, process/bus rule objects
Roles/Skills
The personnel and skill requirements necessary to meet the event derivation
analysis task objectives are identified below.
· Event Modeling Expert
- Expertise in event modeling and object oriented development using object oriented CASE tools
Note: High degree of expertise is required since this task does not outline
full set of techniques necessary for building event models.
· Current Systems Expert
- Knowledge of the functionality of current data utilization
· Target System Functional Expert
- Knowledge of target data requirements
· Redevelopment Expert
- Ability to navigate legacy systems and source code using analysis tools defined within this task and derive events and business rules from the system
Input Requirements
The system components and related inputs required to initiate and complete
the event derivation analysis task are listed below.
Note: See Entrance Criteria section for notes regarding the optional nature
of certain input requirements.
· Environmental analysis documentation including batch run streams, load modules and related source programs
· Functional mapping form 004, built in function hierarchy analysis, that links current program to current function to, optionally, target function
· Function dependency models derived during function dependency analysis task
· On-line screen and batch job data flow diagrams (DFD) derived during general systems architecture assessment
· Inventory and cross reference of user I/O views completed during presentation layer assessment depicting
· Existing application source, JCL, PROCs, screen map definitions and other physical system components
· Batch operations procedures or guidelines
· Optionally, derived process dependency diagram as specified in process hierarchy/dependency analysis task or similar bottom-up effort
· Process mapping form 031, built in process hierarchy/dependency analysis, to link current program to current process to, optionally, target process
Note: Each of above mandatory and optional tasks contribute to the evolution
of LTM. While LTM is listed as optional, managing event derivation across large
models is virtually impossible without formal management facilities.
· Optionally, LTM repository populated with function and process object instances linked to legacy forms, JCL, programs, control tables and other legacy objects
Tool/Technology Support
Technologies supporting the event derivation analysis task include event
modeling, static analysis and open systems repository tools. These planning
tools may provide a vehicle for representing information required as input to
this task.
Event modeling tool
This tool should be able to model events within a business area and support
basic event modeling techniques using the following notations:
Define a business operation as follows:
Define a beginning and an end to event model as follows:
Define an event or stimulus to initiate a trigger as follows:
Support partitioning of an event in order to trigger multiple operations as follows:
Define a trigger to apply business rules in order to determine which operations should be triggered:
Establish a control condition to recognize and accommodate decision points where multiple triggers may initiate an operation.
Accommodate event subtypes based on a given event decomposing into multiple events for clarity or detail.
A complete diagrammatic example is shown below.
This tool should also integrate with modeling facilities used to specify
objects in the object derivation analysis and business rule analysis tasks.
Static analysis tool
Features of a static analysis tool that apply to this task include ability to
graph a program and show decision paths based on that analysis. Decision paths
may be depicted using decision trees, control flow graphs or similar facilities.
One or multiple views of program control flow should provide high-level
paragraph or module names, related hierarchy and decision paths invoking that
hierarchy.
The static analysis tool is used to abstract event subtypes, based on
decisions occurring at the module level, that invoke paths within itself or
another module. Batch and interactive tools may be used for this process.
Open systems repository
An open repository provides the ability to link events with legacy and
business rules objects. This is critical since analysts must examine countless
legacy rules spanning multiple physical components and formats. Without an audit
trail, subsequent business rule specification, rule reconciliation and legacy
rule deactivation is virtually impossible.
Requirements include the ability to reflect event objects, establish type and
other attributes, and relate events to LTM process/bus rule, source and other
objects as defined within this task. A recommended baseline LTM meta-model is
shown in the TIM Appendix section.
Task Steps
The event derivation analysis task is comprised of the following task steps:
