Requirements In Context Part 3: Scope = High-Level Requirements


Part 1 (Just Know It) of this series established the context of requirements being addressed are those that relate to business information systems and that various contexts have an impact on those requirements. Part 2 (The Functional View From 10,000 Feet) addressed the first of these contexts - Functional. That context was further divided into three conceptual levels labelled Functions, Processes and Activities. An example high-level requirement was presented at each of these levels. 


This article moves on to a different context - Project Scope. We will see how scope statements, when making reference to business functionality, lead directly to High-Level requirements. 

Gathering requirements for a business information system is most often done within the context of a project. Approval of a project includes its sponsors signing off on its scope. The scope for a business information system project is typically defined in functional terms. Items in scope make reference to (or should make reference to) business functions, processes and/or activities that are to be delivered.  


NOTE: This series uses the more traditional terms High-Level Requirements and Detail Requirements. In IIBA(R) BABOK(R) Terminology the first of these terms equates to Stakeholder Requirements and the second to Solution Requirements.


A Context Diagram Is Worth A Thousand Words

In addition to the bullet-item list of scope items it is very common for the project initiation document to include a Context Diagram. The objective of a context diagram is to illustrate what is inside the system and what is outside. Things outside the system represent sources and/or consumers of data. The original form of context diagram comes from Dataflow Diagramming (DFD). The top-most level of functional decomposition using DFDs was considered a context diagram. The Unified Modelling Language (UML) Use Case modelling also supports a form of context diagram. Both of these diagramming techniques represent ‘the system’ and both portray things outside the system boundary. The DFD term for these outside things is External Entity. The UML term is Actor. The definition of these two terms is virtually identical. 




A DFD context diagram says nothing about the functions inside the system. That is left to subsequent levels of functional decomposition. Clues are provided by labels given to the dataflows. The Use Case context diagram provides more of a clue to the functions within scope by including named use cases. Dataflows in a DFD context diagram connect only to the system. Actor connectors in a Use Case context diagram connect to one or more specific use cases within the system. 


High-Level Requirements From Project Scope

Examples of high-level requirements were presented in the previous article based on a high-level business function, a medium-level business process and a low-level business activity. We are about to present an example of a project and its scope. As mentioned above, the scope of business information system projects is very often expressed in functional terms. It should therefore be possible to derive high-level requirements from scope items.  


Consider the following situation involving a large hypothetical on-line retailer we will call has a well-established purchase process for its on-line customers. The check-out portion of this process includes activities for identifying the intended shipping address and for providing some form of payment. What the process does not currently include is anything to do with tax on items being purchased. As the result of pressure from various tax authorities this needs to change. 


In establishing a project to deal with this change in the business environment the following scope items were agreed by the business sponsor and signed off: 


  • Maintaining tax-related details for designated tax authorities 

  • Determining applicable tax on items being purchased 

  • Including applicable tax with purchases 

  • Accounting for tax charged 

The Use Case form of context diagram for this example would look like this: 




Scope items will seldom be stated so conveniently that they can be converted one-for-one into the names of use cases. For the sake of brevity, please accept that the scope items in this example are “ones that I prepared earlier.”  


The objective of this article is to show that it is possible to derive high-level requirements based on a project’s scope. The following are examples of such requirements from the scope in this scenario: 


Scope Item 1 - Maintaining tax-related details for designated tax authorities  


The system shall support an administrator maintaining tax-related details required to perform tax determination. This includes establishing tax authorities that are the source of tax rates and to whom collected taxes need to be paid. It also includes mapping of products to tax rates for each authority where there are product-specific rates or specific product types that are tax exempt. 


Because charging tax is new to this organisation there may not be an in-house subject matter expert available when it comes time to sorting out the details for this requirement. Until more is known this high-level requirement acts as an appropriate placeholder for what is likely to be a number of business processes. One would likely be needed for setting up new tax authorities, one for setting up the tax rates and where applicable, one for specifying different rates for different product types. The requirement from a business perspective is fairly straight forward – maintain whatever details are necessary to be able to charge tax. The devil is in the detail.  


Scope Item 2 - Determining applicable tax on items being purchased  


The system shall be able to identify the appropriate tax that applies to the purchase of a given product based on the product type and the tax authority(s) that have jurisdiction where the shipment is to be delivered. 


Where the previous requirement calls for whole new business processes to be supported within the business information system, the functional context of this requirement would be somewhere within the “Identify the shipping address” activity within the “Purchase” process. At this point the product(s) are known and the shipping address details can be used to determine any applicable tax authority(s). Subsequent detail requirements would get into how an appropriate tax rate is determined and specifics of where that rate is used in calculating the total charge to the customer. 


Scope Item 3 - Including applicable tax with purchases 


The system shall present to the customer all applicable tax amounts as part of the purchase process. 


This statement should be sufficient as a high-level requirement from a business perspective. Part of the detailed requirements analysis would include identifying all of the places where the customer ‘sees’ purchase price details. Each of those places will require modification to include whatever tax applies, if any. 


Scope Item 4 - Accounting for tax charged 


The system shall report charged tax amounts as a distinct component of each purchase to the general ledger system identifying appropriate GL Codes and the designated tax authority. 


Wherever money is involved the organisation’s general ledger needs to be kept informed. In this case it is unlikely that there will be any new processes or even activities required. Reporting to the GL will be in place for the current un-taxed purchases. This reporting will just require an enhancement to include the tax amount and its corresponding GL Coding. There should also be an existing Accounts Payable process that handles making payments to suppliers for the organisation. The different tax authorities that are to receive payment of collected taxes should be covered under that process.  


Requirements In Context Part 4 – Keeping High-Level Requirements High-Level

The four requirements derived from the project scope items would not be the only ones for the whole project. But it must be said that they cover the agreed scope of the project, and that they are high level (not slipping into detail). Next time we will look into how to kpreep high-level requirements high-level when dealing with stakeholders that are asked to participate in the context of “Gathering high-level requirements.” 


Author: Dan Tasker


Dan is the author of over 30 requirements-related articles and other resources. His 45+ year career in Information Technology has involved organizations in a variety of industry sectors in the United States, Canada, Australia, and New Zealand. His business analysis experience includes projects involving in-house software development, software vendor solution development, and COTS software acquisition and implementation. He continues to be passionate about quality requirements and helping business analysts produce them. He can be contacted at [email protected].

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Karl Wiegers posted on Tuesday, May 7, 2019 9:45 AM
I think an important aspect of scope definition that I didn't see addressed here is delineating what is in scope from what is out of scope.That is, what is the project (or this portion of it) going to do and what is not going to do. Therefore, I like to include a statement of limitations and exclusions in the scope documentation. Stakeholders might expect that certain capabilities will be included, when in fact an explicit decision was made not to include them. It's a good idea to write those exclusions down for clarity, to help manage expectations.

Another way to use scope definitions is to state which subset of a system's ultimate capabilities will be included in a particular release or iteration. That is, each scope statement represents a defined portion of the ultimate product vision. This is helpful for expectation management with stakeholders and project planning.
Dan Tasker posted on Thursday, May 16, 2019 5:00 PM
I agree completely about the value of 'out of scope' statements. Also, where available, including some form or road map for the in-scope ones. The reason neither of these things were mentioned is that this series is about requirements definition. Scope statements are seen as a given (i.e. an input to requirements definition.
Neetu posted on Thursday, March 26, 2020 9:19 AM
its an informative article. I love reading it.
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