Subject Area/Entity Type Analysis
Objectives
The objective of this task is to use formal data modeling techniques to
document high-level data usage within current systems. This provides a means of
determining overlap between current system data usage and target system data
usage.
This task derives subject areas, entity types and attributes from current
systems. Entities are then linked via the entity relationship diagram. This
approach, using rationalized data definitions as input, is expanded to greater
detail under Transformation.
The number of resulting models depends on the systems being assessed.
Specific objectives for this task include the following:
· Define a subject area/entity relationship diagram for each system being assessed
· Define an integrated subject area/entity relationship diagram representing all systems being assessed
The following points are optional based on redevelopment objectives:
· Perform gap analysis between current and target subject area diagrams (individual or integrated bottom-up views)
· Summarize similarities and discrepancies between current and target subject areas and entity relationships
Note: Refer to Comsys-TIM appendix for more information on LTM.
· Establish an ongoing gap analysis facility using legacy transition meta-model (LTM) to reflect current logical to current physical and current logical to target logical data mappings
This figure overviews subject area/entity relationship analysis. Existing
data definitions captured during data definition analysis are input to the data
model derivation process. For systems undergoing strategic redesign, current
entities are mapped to top-down data models. This "gap analysis"
provides planning input to a variety of data migration and redesign scenarios.
Entrance Criteria
The entrance criteria for the subject area/entity type analysis task are
listed below.
· Completion of objective setting/proposal development
· Completion of the data definition analysis and availability or primary I/O record definitions
Optional - if no replacement is envisioned and there is no pre-defined
current to target mapping requirement
· Completion of top-down subject area analysis and entity relationship (ER) diagram for this business area
Optional - based on availability:
· Completion of Enterprise Redevelopment Planning, data architecture assessment task identifying shared data stores
· Population of LTM model as completed in entrance criteria tasks
Roles/Skills
The personnel and skill requirements necessary to meet the subject
area/entity type analysis task objectives are identified below.
· Current Systems Expert
- Knowledge of existing data structures and databases
- Knowledge of existing functional data requirements
· Target Functional System Expert
- Knowledge of target functional data requirements
· Metric Analyst
- Ability to assess & record architectural metrics
· Data Modeling Expert
- Expert at building bottom-up and top-down data models
· Repository Administrator
- Ability to update repository attribute, entity and relationship
object instances based on task guidelines
Input Requirements
The system components and related inputs required to initiate and complete
the subject area/entity type analysis task are listed below.
· I/O record groupings list from data definition analysis
· Primary I/O record definitions (layouts) from data definition
analysis
· The current physical systems environment including access to
program, Copy or DDL source code
· Access to active data dictionaries defining record, segment and
schema definition
The following objectives are optional based on redevelopment objectives and
unique scenario driving this assessment effort.
· Subject area and entity relationship diagram for target business area/system
· Blank data entity mappings section of functional assessment Form 005-2
Optional - where available
· Legacy transition meta-model (LTM) populated with all system components and relationships based on use in prior Comsys-TIM tasks
· Business Area/Data Store Matrix Form 041 defining major data stores that cross functional business area boundaries
Tool/Technology Support
Technologies supporting the subject area/entity type analysis task include
data reverse engineering, spreadsheet, open systems repository and word
processing tools. These tools are used to represent information as required by
this task.
Data Reverse Engineering Tool
Tools for this task focus on the capture, import and manipulation of data
definitions (and in some cases physical data) with the intent of deriving a
logical model. This is typically in the form of an entity relationship model for
this task. Features include:
Note: Various capture tools support COBOL, PL/I, IMS DBD and DB/2 DDL as
input to process.
· Ability to capture existing data definitions including source program layouts (COBOL, PL/I, etc.), relational tables, schema and other formats
· Ability to represent records as entities and elements as attributes in a tool encyclopedia
· Optional ability to apply artificial intelligence to captured data representations to create an ER model
· Optional, but highly recommended for tasks where multiple systems are involved, ability to merge multiple models (bottom-up and/or top-down)
· Optional ability to capture record layouts and input physical data value to derive an ER model
· Optional, based on scenario requirements, top-down planning/analysis level modeling support
Open systems repository
A repository provides an important, yet optional, capability to link business
areas, systems and components using the legacy transition meta-model. In this
task, a repository is used to establish current entity, attribute and
relationship objects and map these logical objects to physical records and
elements. Finally, current entities/attributes may be mapped to target
entities/attributes as defined in task guidelines.
Spreadsheet
This tool is used to record metric results for this task.
Word processor
This is required to record analysis results.
Task Steps
The subject area/entity type analysis task is comprised of the following task
steps:
