The Importance of Data Analysis in Producing a Robust Physical Data Model

The Importance of Data Analysis in Producing a Robust Physical Data Model

By Declan Chellar

Hierarchy of Data Analysis

When “data modelling” is mentioned on

projects…


Physical Data Model


projects…

…too many people only think of the

physical data model, DB tables, etc.


Physical Data Model


projects…

…too many people only think of the

physical data model, DB tables, etc.

But what about the data analysis that leads to a robust

physical data model?


Conceptual Data Model• A fundamental part of the

information architecture




• Identifies the business entities and shows the relationships between them





• An essential complement to the business architecture






• Ought to be in place before any related software project even starts!






• Ought to be in place before any related software project even starts

• In reality, often missing altogether


Logical Data Model(normalised)







• Expands upon the CDM by identifying the attributes of each entity and the keys to each relationship






• Normalised to reduce redundancy







• Ideally in place before any related software project even starts



Data Dictionary





Data Dictionary



• Provides the essential business definitions for each attribute identified on the LDM



Data Dictionary




• Traceable back to the LDM



Data Dictionary








Data Dictionary






• Can be enhanced iteratively throughout requirements gathering



Data Dictionary

Process Steps(data in/out at the functional level)


requirements definition



Data Dictionary




• For any process step, identifies the relevant attributes



Data Dictionary





• Traceable to/from the Data Dictionary



Data Dictionary






• Its elaboration can feed details back into the Data Dictionary



Data Dictionary







• In reality, often contains details that should reside in the Data Dictionary, leading to redundancy



Data Dictionary


Screen Specification(fields, etc., required for screens)





Data Dictionary





• Documents the required behaviour of each screen and the relevant data to be displayed or captured (not to be confused with screen design/layout)



Data Dictionary









Data Dictionary







• Should be documented after the relevant logical process steps



Data Dictionary







• Should be documented after the relevant logical process steps

• In reality, often contains details that should reside in the Data Dictionary, leading to redundancy



Data Dictionary



Conceptual Data ModelRobust data analysis

provides the basis for good physical data modelling



Data Dictionary



Conceptual Data ModelRobust data analysis

provides the basis for good physical data modelling

Otherwise, the data architects might have to

reverse-engineer the data needs of the business

based on screen designs



Data Dictionary



Conceptual Data Model

Physical Data Model



Data Dictionary




Physical Data Model

This takes a little longer, but results in a robust, adaptable and durable

physical data model




Physical Data Model




Physical Data Model

This is sub-optimal and is likely to result in an

inefficient database that will under-perform as it

grows larger




Physical Data Model

This is sub-optimal and is likely to result in an

inefficient database that will under-perform as it

grows larger

Unfortunately, this approach is quite common



Physical Data Model



Physical Data Model

This worst-case-scenario will definitely lead to an

under-performing database within as little as six months



Physical Data Model

This worst-case-scenario will definitely lead to an

under-performing database within as little as six months

Unfortunately, this approach is not uncommon


Of course, physical data models often come “out of

the box” in the case of BPM or ERP systems


However, “out-of-the-box” does not mean “magic“ and the PDM does not

automatically fit the data needs of the business


“Out of the box”Physical Data Model

The PDM must be tailored to suit the

specific needs of the business





Data Dictionary





Data Dictionary

Otherwise, there will be a significant gap between

the PDM and the business needs it should support


“Out of the box”Physical

Data Model



Data Dictionary

Once in production, this gap eventually becomes a chasm


And, financially, that chasm can feel like a

bottomless pit

REMEMBER!


Physical Data Model€

€

€$$ $

£ £

£

REMEMBER!

Functional Specification(data required for process steps)


Physical Data Model€ €

$

$£

£

REMEMBER!


Data Dictionary

Functional Specification(data required for process steps)



Physical Data Model

€

$

£

REMEMBER

“Out of the box”Physical

Data Model



Data Dictionary€€

€$$ $

£ £

£

REMEMBER!




Data Dictionary

€

$

£

With thanks to the following for reviewing the draft slideshow:

• Simon Duckett, Enterprise Data Architect• Jonathan Hunsley, Senior Business Architect

www.chellar.com/blog

The Importance of Data Analysis in Producing a Robust Physical Data Model

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