Welcome!

Microsoft Cloud Authors: Janakiram MSV, Yeshim Deniz, David H Deans, Andreas Grabner, Stackify Blog

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

Database Modeling with Object Role Modeling - Part 3

Modeling constraints commonly enforced in relational database systems

  • Database Modeling with ORM - Part 2
  • Object Role Modeling - Part 1: A Picture Is Worth a Thousand Words

    This article is the third in a series introducing Object Role Modeling (ORM). ORM is an excellent modeling methodology you can use to construct the conceptual database model. It is an approach to describing data in terms of objects and the roles they play.

    The focus of the first article (.NETDJ, Vol. 1, issue 10) was working with domain experts to identify the various object types and fact types that need to be included in the conceptual model. It introduced you to the various common types of predicate arities as well as the use of Visio to construct an ORM source model. The second article (.NETDJ, Vol. 1, issue 12) continued the study of ORM source modeling. The process of developing the database model is iterative and involves the continual refinement and verification of the various fact types and object types that make up the model. It introduced some of the concepts involved in the refinement process and focused on the concepts of primitive entity types, subtypes, derived fact types, and unique constraints.

    This article examines the process of modeling other types of constraints commonly enforced in relational database systems. It focuses on constraints such as external uniqueness, disjunctive role, and set constraints. In addition, it covers applying population checks to verify the conceptual database model.

    Uniqueness Constraints, Reference Schemes, and Mandatory Role Constraints
    Enforcing constraints is fundamental to designing the structure of a relational database. There are many different types of constraints to consider when defining the model. For example, Figure 1 shows a fact type with an arrow placed above the student role box in the predicate phrase. The arrow models a frequency constraint indicating that a student has at the most one SSN. Figure 1 also models a mandatory role constraint. The dot on the line connecting the student role to the predicate phrase indicates that each student must have a SSN. Figure 2 further constrains the roles in the fact type. It places similar constraints on the SSN role making it mandatory and unique. A student and SSN combination must be unique in the database. Since a student's SSN is unique, it can distinguish between different instances of the student entity. A unique constraint used to distinguish between identity types is the primary unique constraint (PUC) and modeled by tagging the constraint with a P. The PUC of an entity type is referred to as its reference mode, and it is often more convenient to indicate the reference mode by placing it in parenthesis within the entity role shape. Figure 3 demonstrates the two ways of modeling a reference mode.

    Up to this point, the constraints modeled have been internal to a particular fact type. When defining constraints, you must also consider external constraints that apply across a group of fact types. For example, students can have the same first name and/or the same last name but the combination of first name, middle name, and last name must be unique. To symbolize external uniqueness constraints in ORM, a dashed line connects the roles involved in the constraint to a circled letter U symbol (see Figure 4). There may be times when an external uniqueness constraint uniquely identifies instances of an entity type. This type of constraint is a compound reference scheme and a P replaces the U in the model (see Figure 5).

    In modeling external constraints sometimes it is necessary to model exclusive, or constraints. For example, it is necessary to be able to contact students by phone. Students must have either a home phone or a cell phone or both. In ORM terminology, this is a disjunctive mandatory role constraint (see Figure 6). Dashed lines connect the roles involved in the constraint to a circle symbol containing a solid dot.

    Constraint modeling in ORM is very robust and ORM can represent very intricate constraints as part of the conceptual model. Set constraints restrict the population of two roles and are primarily external in nature. They come in three flavors: exclusion, equality, and subset constraints. Exclusion constraints prevent instances of one set from appearing in another. The exclusion constraint symbol consists of a circled x with dashed lines connecting the roles involved in the constraint (see Figure 7). This constraint restricts the classifications of instructors to either full-time or part-time.

    An equality constraint ensures that all instances of one set appear in a related set. Figure 8 shows an equality constraint stipulating that full-time instructors get a salary. This is in contrast to part-time instructors who get a stipend. Notice that the symbol for this type of constraint is an equality symbol. A subset constraint ensures the instance of one set is also included in the instance of another. Figure 9 shows a subset constraint stipulating department chairs must also be full-time instructors. The symbol for the subset is a sideways underlined U. Notice that an arrow head has been added that points to the superset.

    Modeling External Constraints Using Visio
    The following activity demonstrates adding external constraints to a Visio ORM model. Note: You need Visio for Enterprise Architects in order to create an ORM Source Model.

    1.  Start up Visio. On the File menu, choose New > Database > ORM Source Model.

    2.  If the Business Rules Editor is not visible at the bottom of the window, on the Database menu, choose View > Business Rules.

    3.  Double-click the first Object Type cell in the Business Rules Editor. Create an Instructor entity object type with a reference mode of EmpNo. Repeat this procedure to add the rest of the object types shown in Figure 10.

    4.  Select the Fact Types tab at the bottom of the Business Rules Editor. Press the F2 key to launch the Fact Editor window. Using the left Object dropdown choose Instructor. In the relationship textbox enter "is a". In the right object drop down choose Full Time Emp. Repeat this procedure to add the rest of the fact types shown in Figure 11.

    5.  Click and drag the fact types "Instructor is a Part Time Emp" and "Instructor is a Full Time Emp" from the Business Rules Editor onto the drawing surface.

    6.  Select both fact types on the design surface by clicking on the predicate phrases while holding down the shift key. Right click on one of the predicate phrases and choose Add Constraints, which launches the Add Constraint dialog box.

    7.  Select exclusion from the constraint type dropdown and select the instructor role in each of the predicate phrases listed by clicking in the role box (see Figure 12). Click OK to close the Add Constraint dialog. The resulting diagram is similar to that in Figure 7.

    8.  Experiment with adding the various types of constraints. See if you can construct a diagram similar to that in Figure 13.

    Verifying the Conceptual Model using Verbalizations and Population Checks
    One of the most powerful features of ORM is the ability to verify the model with the domain experts using verbalizations and population checks. Verbalizations are natural language statements of the fact type and applied constraints that domain experts can easily understand and verify. Providing an ORM diagram such as Figure 14 to the domain experts for verification would not be very effective. Instead, a verbalization of the fact type is generated that can be easily understood and verified against the data artifacts that have been collected. Figure 15 contains the verbalization of the fact type of Figure 14. Using Visio, you can export the verbalizations of the various fact types contained in the model to a report. This report is very useful to the domain experts when they verify the model.

    Population checks are an extremely useful way to verify the accuracy of the constraints modeled. Sample populations represent data from a variety of sources such as reports and forms that currently exist to maintain and manage the data. In order to achieve a valid and useful population check, the sample data must be actual real world data and not fictitious data created to conform to the constraints of the model. Figure 16 shows a sample population entered for the fact type in Figure 14. Using the sample population, Visio can verify the constraints, report any errors and make recommendations for modifying the constraints. In order for a proper analysis, it is important that the sample population is large enough to be statistically significant.

    Analyzing Constraints Using Visio
    1.  Start up Visio. On the File menu, choose New > Database > ORM Source Model.

    2.  If the Business Rules Editor is not visible at the bottom of the window, on the Database menu, choose View > Business Rules.

    3.  Double-click the first Object Type cell in the Business Rules Editor. Create a class object type, room object type and a time value type.

    4.  Select the Fact Types, tab at the bottom of the Business Rules Editor. Press the F2 key to launch the Fact Editor window. Construct the ternary fact type using the settings shown in Figure17. Add the constraint settings using the constraint tab shown in Figure 18.

    5.  Select the Examples tab and enter a sample population as shown in Figure 16. Click the Analyze button and examine the results. Experiment with changing the sample population to see how it affects the resulting analysis.

    6.  Close the Fact Editor and drag the fact type to the design surface.

    7.  Under the Database menu, select Report. The New Report Wizard launches. Select the Fact Type Report, click Next, and then finish. Experiment with the different report setting options and preview the report.

    Review
    This article concludes this series on Object Role Modeling. ORM is an excellent aid to modeling the data and data relations that will comprise the backend database structure of your application. The real strength of ORM is its ability to extract the business data requirements from the domain experts into a conceptual model that is easily understood and verifiable by those same domain experts. By spending time creating a thorough and accurate conceptual model, the application's chance of success as it progresses to the logical and physical stages significantly increases.

    The goal of this series was to give you a sufficient introduction into the process of ORM modeling with Visio so that you are comfortable enough to start experimenting with the process. As you become more comfortable with ORM and Visio, you will gain an appreciation of its capabilities and benefits. Remember that the ORM model does not replace the traditional entity relationship model. ORM captures the conceptual requirements while the ER model describes the logical requirements. Once the ORM model is developed, you can use Visio to create and refine the logical and physical models of the relational database system. Although this series of articles did not cover the process of developing the logical and physical database models, it may be fodder for a future series. Let me know if this would be of interest to you.

  • More Stories By Dan Clark

    Dan is a Microsoft Certified Trainer, Microsoft Certified Solution Developer, and a Microsoft Certified Database Administrator. For the past seven years he has been developing applications and training others how to develop applications using Microsoft technologies. Dan has been developing and training Microsoft's .NET technologies since the early betas. He has recently authored the book "An Introduction to Object-Oriented Programming with Visual Basic .NET," published by Apress.

    Comments (0)

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    @ThingsExpo Stories
    SYS-CON Events announced today that Synametrics Technologies will exhibit at SYS-CON's 22nd International Cloud Expo®, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Synametrics Technologies is a privately held company based in Plainsboro, New Jersey that has been providing solutions for the developer community since 1997. Based on the success of its initial product offerings such as WinSQL, Xeams, SynaMan and Syncrify, Synametrics continues to create and hone inn...
    To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
    With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...
    Recently, WebRTC has a lot of eyes from market. The use cases of WebRTC are expanding - video chat, online education, online health care etc. Not only for human-to-human communication, but also IoT use cases such as machine to human use cases can be seen recently. One of the typical use-case is remote camera monitoring. With WebRTC, people can have interoperability and flexibility for deploying monitoring service. However, the benefit of WebRTC for IoT is not only its convenience and interopera...
    The 22nd International Cloud Expo | 1st DXWorld Expo has announced that its Call for Papers is open. Cloud Expo | DXWorld Expo, to be held June 5-7, 2018, at the Javits Center in New York, NY, brings together Cloud Computing, Digital Transformation, Big Data, Internet of Things, DevOps, Machine Learning and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding busin...
    Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
    No hype cycles or predictions of a gazillion things here. IoT is here. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, an Associate Partner of Analytics, IoT & Cybersecurity at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He also discussed the evaluation of communication standards and IoT messaging protocols, data...
    Product connectivity goes hand and hand these days with increased use of personal data. New IoT devices are becoming more personalized than ever before. In his session at 22nd Cloud Expo | DXWorld Expo, Nicolas Fierro, CEO of MIMIR Blockchain Solutions, will discuss how in order to protect your data and privacy, IoT applications need to embrace Blockchain technology for a new level of product security never before seen - or needed.
    In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
    A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
    Cloud Expo | DXWorld Expo have announced the conference tracks for Cloud Expo 2018. Cloud Expo will be held June 5-7, 2018, at the Javits Center in New York City, and November 6-8, 2018, at the Santa Clara Convention Center, Santa Clara, CA. Digital Transformation (DX) is a major focus with the introduction of DX Expo within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive ov...
    "Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, discussed how they built...
    Digital Transformation (DX) is not a "one-size-fits all" strategy. Each organization needs to develop its own unique, long-term DX plan. It must do so by realizing that we now live in a data-driven age, and that technologies such as Cloud Computing, Big Data, the IoT, Cognitive Computing, and Blockchain are only tools. In her general session at 21st Cloud Expo, Rebecca Wanta explained how the strategy must focus on DX and include a commitment from top management to create great IT jobs, monitor ...
    "Digital transformation - what we knew about it in the past has been redefined. Automation is going to play such a huge role in that because the culture, the technology, and the business operations are being shifted now," stated Brian Boeggeman, VP of Alliances & Partnerships at Ayehu, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
    SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
    Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
    22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
    22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...