My Love with SQL Server

CDIs-Non Functional Requirements-Other few May 21, 2013

In the series of CDIs-Non Functional Requirements I had covered on NFRs like Performance, Scalability, Availability, Reliability, and Utilization Benchmarks that could be useful to build a CDI system. In this post I shall talk about less known but important NFRs like Maintainability, Extensibility and Security. I wouldn’t term these as NFRs but questions on these topics will help you to get an insight on how the system is expected to behave, from a business and technical perspective. Also, these don’t work in silos, instead are linked back to some of the ones mentioned in the above list.

Maintainability

1. What is the maintenance/release cycle?
   

   This question will give us an idea on the practices that is followed by the business and technical teams about the release cycle. And each release cycle would mean there would be change in the source system which may be applicable to down-stream applications. The more the release cycles, the difficult is the job of maintaining code base. And to avoid long-term overheads the system, data model and the low level design of the ETLs should be carefully built considering that this changes would be constant, and frequent.
   

2. How frequently do source or target structures change? What is the probability of such change?
   

   This point is relevant to the first question, but elicits information one level deeper by asking “if more maintenance cycles, what are those changes at source and expected to be in target”. If the changes are constant, frequent and less complex then the data model and the ETLs have to be configurable to accommodate ‘certain’ changes in the source. The configurability comes with a rider and tradeoff on other NFR like performance. The changes on data source could affect the performance of the ETL and sometimes the business laid SLA can’t be met.
   

Now having said this, I presume the next NFR will be closely related with Maintainability.

Configurability

The answers to queries under this topic is supposedly to be challenging for the business, and technical teams. Not everyone is sure of what should be configurable and what shouldn’t be based on the changes that are expected from business at the source system level. One would get the answer of “not sure”, “may be”, “near future quite possible”, “probably” the source will change, and what change will remain as a question. The challenge of providing an appropriate solution at different layers will be a daunting task for the technical team.

1. How many different/divergent sources (different source formats) are expected to be supported?
   

   The answer to this question will help in understanding what formats of sources (csv, tsv, xml..etc…) have to be supported, and if there is plenty of difference then alternate design practices could be implemented on the target which could provide extensibility to all formats.
   

2. What kind of enhancements/changes to source formats are expected to come in?
   

   An answer to this point would help in deciding if there be abstract transformations or reusable mappings.
   

3. What is the probability of getting new sources added? How frequently does the source format change? How divergent will the new source formats be?
   

   This information will help in knowing how often the sources format change, and is it with existing sources or with new ones. Again it would also help in deciding between abstract transformations or reusable mappings.
   

The last NFR is Security which is usually the last preferred in any system architecture and design, but most important.

Security

In case of CDI we are dealing with sensitive information of the customer and the transaction details. It is important to understand how business treats this type of data, and how do security compliance team want to consider the data is being gathered from different source systems and consolidated at a single place – “Data hub”. The below bunch of questions cover on the data protection level rather than access levels or privileges of different users.

1. Are there any special security requirements (such as data encryption or privacy) applicable?
   

   An answer to this question usually would be “no”, but there are certain fields that are brought in from CRM and ERP systems and needs to be hidden from any misuse in case of breach of security. It is suggested that this question is explained well with a real scenario, and then a decision of having data or database encryption enabled or not could be taken.
   

2. Are there any logging and auditing requirements?
   

   This is least required since the data from different systems is mostly massaged and made available in reporting format through a different data sink. A discussion in here would help in deciding if the security should be handled at reporting level (enabling different security features), rather than in massive data processes.
   

I hope all these posts on NFR for CDIs helps you in architecting, designing Data Hub system that is highly available, scalable, high performing, and most reliable.

Cheers!