Building the Security Model Requirement

7/30/2019 Building the Security Model Requirement

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Building the Security Model with Use Case and Class Models

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In writing a business requirements document (BRD), the business analyst needs todocument who can access the solution (assuming software) and what data can becreated, updated, read, and deleted (CRUD). In other words, a security model thata security analyst can build access profiles with the appropriate privileges. Thisarticle provides the business analyst a method for documenting a security model inthe BRD based on information extracted from Use Case and Class models. Thissecurity model consists of three matrices with traceability from stakeholders to thedata entities that they need to create and/or manipulate:

Stakeholder / Use Case Actor Matrix

Use Case Actor / Use Case Matrix

Use Case / Data Entity Matrix

Note: this article assumes that the reader understands use case and class models.

A necessary component of the business requirements document (BRD) is the security model (nonfunctionalrequirement). The business analyst can utilize two models, Use Case (functional requirements) and Class (datarequirements), for this purpose. To illustrate this, this article utilizes a use case and a class model for a Student RecordSystem as an example. Note the models in this article are high-level in order to focus on the information needed to buildthe security model (i.e., only the use case diagram, not its description, is depicted here).

Student Record System Analysis

During the analysis of a student record keeping area for a university, the business analyst discovers the following

stakeholder goals through interviews and facilitated meetings:

professors create, read, update, and delete student course grades

department heads create, read and update student transcripts (not delete), and read student course grades

students read their course grades and transcripts

students also create, read, update, and delete campus interests

The business analyst also notes the following business rules:

only professors maintain student grades*

only department heads maintain student transcriptsand transcripts are never deleted**

The business analyst documents the goals in a use case diagram under the constraints of the business rules. In Figure 1,a context bias use case diagram is shown. The diagram exhibits the boundary of a proposed Student Record Systemwith several use cases (goals) and the associated actor roles. Besides the use case and actor associations, the businessanalyst also documents generation-specialization associations between the respective roles:

Grade Reader and Campus Interest Creator

Grade Reader and Grade Creator

Grade Reader and Transcript Reader; Grade Reader and Transcript Creator (through inheritance)

Transcript Reader and Transcript Creator

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Figure 1. Student Record System Use Case Diagram

Security Model Three Matrices

Together with the use case diagram, the business analyst builds a Stakeholder / Use Case Actor Matrix associatingstakeholders with the needed actor role to accomplish their goals (x in the intersecting cell); see Figure 2. Note astakeholder can have multiple roles.

Figure 2. Student Record System Stakeholder / Actor Role Matrix

Along with the above matrix, the business analyst also builds an Actor Role / Use Case Matrix which can be read off theuse case diagram. The x in the intersection cell associates actor roles with use cases.

Figure 3. Actor Role / Use Case Matrix

(Note if there is an additional business rule that limits professors to maintaining grades only for students in theirclasses, the business analyst needs to reference this rule within the Create Grade use case description.)*

The third and final matrix for our security model is the Use Case / Class matrix. For this matrix, the business analystdocuments the use case data needs in a Class model. The business analyst draws information for the Class model fromthe use case descriptions (not shown) via a noun analysis of the use case scenarios.


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Figure 4. Student Record System Class Model

From the data defined in the Class model and how the data are manipulated in the use case scenarios under theconstraints of the business rules, the business analyst builds a Use Case / Class Matrix associating Use Cases with theClasses that they create, read, update, delete (CRUD); see C,R,U,D in the intersecting cells on Figure 5.

Figure 5. Use Case / Class Matrix

(Note absence of D, for StudentTranscript Class per business rule)**

Traceability

From these three matrices (Figures 2, 3, 5), a security analyst can build the required security access profiles. Thematrices provide a security model with forward and backward traceability (Figure 6) that a security analyst can use tolink each stakeholder who needs access (use case actor) through each functional requirement (use case) to the data(class) that the stakeholder needs to create and/or manipulate.

Figure 6. Forward and Backward Traceability Security Model

Summary and Special Note

This article provides a business analyst a method for documenting a security model in the BRD. The model consists ofthree matrices based on information extracted from Use Case and Class models. A security analyst uses the securitymodel to build access profiles with the appropriate privileges. Note: This article does not address the security approachof securing all data or only securing sensitive data. Regardless of the approach, the matrices still apply. In addition, it isa best practice that access profiles have expiration dates. This ensures that the security analyst reviews the profiles forvalidity on a scheduled basis. Typically, the security organization determines the security approach and recommendsexpiration dates.


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Author:Mr. Monteleone holds a B.S. in physics and an M.S. in computing science from Texas A&M University.He is certified as a Project Management Professional (PMP) by the Project Management Institute (PMI), aCertified Business Analysis Professional (CBAP) by the International Institute of Business Analysis (IIBA), aCertified ScrumMaster (CSM) and Certified Scrum Product Owner (CSPO) by the Scrum Alliance, and certified inBPMN by BPMessentials. He holds an Advanced Masters Certificate in Project Management (GWCPM) and a

Business Analyst Certification (GWCBA) from George Washington University School of Business. Mark is thePresident of Monteleone Consulting, LLC and can be contacted via e-mail [email protected].

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Building the Security Model Requirement

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