Originally published August 16, 2007
The Business Intelligence Network has published a research study on data warehouse appliances, which can be found at www.BeyeRESEARCH.com. In preparing this study, we have talked with a number of colleagues and came to the conclusion that the term appliance is often misunderstood and misused within the information technology (IT) industry.
This article suggests a set of criteria for defining and evaluating an appliance as a generic term in the context of information technology. The article expands upon a section in the research study and extends it into evaluating general types of appliances. The article does not specifically address appliances for data warehousing or other IT roles.
The term appliance emerged in the early 1900s when electricity started to power household devices, like washing machines. Before then, electric motors were used as source of power for many devices. An appliance was initially considered a luxury because an expensive and multipurpose component (the electric motor) was used for a limited single purpose.
According to Merriam-Webster Online, the first definition of appliance is the "act of applying" which means to put to use for a practical purpose. The second definition is a piece of equipment (tool or device) "designed for a particular use or function" to enable the act of applying.
Note that the use of a universal energy input is an aspect of the definition. This characteristic is why we usually do not consider a toilet or bicycle to be an appliance.
For this article, the term appliance is:
Equipment that is designed for a special purpose and enables a practical function.
In general terms, an appliance is a solution to solving a problem by enabling the proper function. Hence, the evaluation of an appliance involves judgments about the completeness and effectiveness of the solution, as discussed later.
Ordinary household appliances, such as toasters, can be used to illustrate this definition. A toaster enables us to do the practical and specific function of browning bread so that butter and jam can be properly presented for consumption.
A search of the websites for Sears, Target, and Wal-Mart produced some interesting observations about toasters:
This discussion illustrates the difficulty of applying the term appliance meaningfully to ordinary products. This is especially true for IT appliances. A vendor can label any product as an appliance; however, the challenge is to understand the intended implications of that label.
We suggest that there are three criteria for evaluating an appliance – purpose, convenience and value, as described below.
According to our definition, an appliance is designed for a specific purpose, which puts the burden on how purpose is defined. A quote by Albert Einstein is appropriate: "Everything should be made as simple as possible, but not one bit simpler." Hence, an appliance must encapsulate its purpose in the simplest manner possible, but not one bit simpler. This is quite a challenge and places the burden on both the vendor and consumer of the appliance to define its purpose properly.
We suggest that there are three aspects to defining purpose: scope, design and ends.
Returning to Webster's definition, an appliance is designed for a specific purpose. But, what level of specificity is required?
For instance, an oven can brown bread and thus make toast. Is an oven also an appliance? Is an oven any less of an appliance than a toaster? This point is that a toaster has a narrower scope than an oven, while an oven has a broader scope with a more general purpose.
Is a narrow scope better than a broader scope? Applying Einstein's principle, the scope should be as narrow as possible for its purpose, but not one bit narrower. In other words, the best scope is one that provides a complete solution for what is needed with no more or no less functionality.
The purpose should be reflected in the design of the appliance. The expression purpose-built is often used to imply this point. A good example is Danish furniture whose form has an artistic harmony with a practical function.
The nature of the design can vary because there are several ways of instilling purpose into the design of an appliance. Consider the differences between native appliances and packaged appliances.
A native appliance is one whose components are designed specifically for the appliance and tightly integrated into the solution. The advantage comes from using "best-of-breed" components, but the reusability of components for other purposes may be limited (which given the short life of these components may not be important).
A packaged appliance is one whose components are standard and mass produced according to de facto or de jure standards. The advantage comes from properly configuring standard components, incrementally evolving those components over time, and the ability to reuse components.
A related question is whether an appliance can consist of only software without hardware. Our position is that the term appliance is appropriate if the hardware is insignificant in fulfilling the purpose of the appliance. This would be the case if the required hardware is readily available and assumed to be part of the current infrastructure.
Evaluating the design of an appliance involves complex judgments about whether the design provides a complete solution in an effective manner.
Ends, Not Means
The purpose of an appliance should be defined in terms of what it does, rather than on how the function is achieved. In other words, the emphasis should be on the ends, rather than on the means.
For example, the purpose of a toaster should be described in terms of the quality of browning and the types of bread, rather than the way that electricity heats the bread or how the timer pops the bread up at the right moment. Stating the ends, instead of the means, may be simple for toasters, but imagine the complexity of an appliance.
The next sections add convenience and value to the criteria for evaluating appliances.
The second criterion for evaluating an appliance is convenience, which is described in terms of ease of use, simplicity and compatibility.
Ease of Use
Ease of use is defined as the amount of required time, effort, and resources to use an appliance. Ease of use relates to all phases in the product life cycle from selection, purchase, deployment, operation, administration and retirement.
Ease of use for deployment is the effort needed before you can use the appliance and is often called time-to-value, a critical factor for appliances. In other words, an appliance should be plug-and-play like plugging in the toaster and making your toast, with its purpose achieved within a few minutes. Ease of use for operation and maintenance is the effort required to use and operate the appliance. In this case, ease of use is highly dependent on appliance architecture, as discussed in the earlier section of this article on Design.
An appliance should encapsulate all the necessary components into a single integrated package that appears as a black box to external users. Only the set of external features necessary for its purpose should be visible to the user.
If a user cares what is inside the appliance package, this indicates a problem. Either the user is a control freak who is unwilling to trust the appliance vendor, or the appliance vendor has created a poor design requiring the user to crawl inside. Do you care what is inside your toaster?
This criterion is particularly important for the configuration of IT appliances. With proper encapsulation, the only parameters visible to the user of the appliance are those that are directly related to its purpose. Configuration should not require special skills unrelated to the purpose of the appliance or require detailed knowledge of its internals.
For instance, a toaster should only have controls related to toasting (light or dark) and not to the temperature of the heating element or to the duration of heating.
The compatibility2 of an appliance implies a harmony with its environment. A toaster should be compatible to its power source. If you plug a U.S. appliance (using 110 volts) into a European power outlet (supplying 220 volts), sparks will fly.
With IT appliances, compatibility becomes a difficult issue that involves the harmony with complex infrastructures. A simple adapter will make the U.S. appliance compatible with the power outlet mechanically, but that compatibility is not sufficient electrically.
The third criterion for evaluating an appliance is value, which is described in terms of alignment, cost and performance.
The criterion of alignment is having the purpose of the appliance aligned to business requirements. Without this alignment, there can be no value attributed to the appliance.
For instance, a bagel shop requires a toaster that can handle bagels. However, some toasters have a problem because the bagel is too thick and gets stuck inside. The purpose of those toasters is not aligned to the required business requirements; therefore, the appliance cannot deliver value.
The cost of an appliance is much more than its purchase price. It is often much more complex, involving an estimate of the total cost of ownership (TCO) across all of the product life cycles. Hidden may be significant intangible costs, such as education, electrical power and space requirements.
An important factor related to cost is time to business value. Even if the TCO is low, the appliance will not be a good investment if the time to provide business value is excessive.
The performance of an appliance is based on its performance for achieving its purpose. For instance, the performance of the toaster should be related to toasting a slice of bread. Other aspects are irrelevant.
Each of these purposes will have different performance requirements. Even in these cases, however, performance may involve many interrelated factors, such as the number of users, and workload, query and schema complexity. When the business purpose is complex, a proof of concept may be required before actual performance can be estimated.
Another factor related to performance is scalability. When we want to upgrade from a two-slice toaster to a four-slice one, we would normally just replace the toaster. In the IT world, this approach may not be acceptable. Instead, there may be the need to upgrade the appliance in place as performance and scalability requirements increase.
And, a final factor of performance is the reliability or the dependability of an appliance to perform its purpose. For instance, a toaster is reliable if it does what it is supposed to do all the time. Some IT systems require 24 by 7 operations with four 9's (or 99.99 percent) reliability and offsite disaster recovery capabilities, whereas others have less stringent requirements.
We have discussed nine criteria for evaluating an appliance based on purpose, convenience and value. A summary of these criteria is shown in Figure 2.
Figure 2: Summary of Evaluation Criteria
Note that the figure implies that the value criteria are the foundation, upon which the convenience criteria and then purpose criteria build. In other words, the value must first be present to allow the other criteria to be considered.
The evaluation of an appliance, especially within information technology field, is a complex task. To aid with this task, we suggest that there are three general classes of appliance and that a chart can be used to visualize the profile of an appliance.
First, appliances can be classified according to which criteria are the strongest. For instance, there are three classes of appliances based on the criteria for purpose, convenience and value, as follows.
An appliance will be, in reality, a mixture of these classes, but there will be a tendency to emphasize one over the others.
Second, we offer an evaluation worksheet using an Excel spreadsheet as shown in Figure 3. It lists the nine criteria, along with specific questions for each. Each of the criteria can be rated on a five-point scale, with five being "very high." The XLS file is available here.
Figure 3: Excel Spreadsheet Example
Third, we offer a chart using a radar-like profile of the nine criteria, which is a better visualization to see the balance among the criteria. For example, Figure 4 shows the profile for a high-convenience appliance, with high scores for ease of use, simplicity and compatibility.
Figure 4: Profile for a High-Convenience Appliance
Of the three dimensions, the value criteria of alignment of purpose, total cost of ownership, time to business value, performance, and reliability are important deciding factors in acquiring an appliance. These decision criteria are unique to each business. So, the best appliance for one company is not necessarily the best appliance for another.
A more realistic profile of an appliance's strengths is shown in Figure 5. In this case, this appliance is strong in performance and design, while its simplicity is weak. Hence, the use of this appliance requires more resources, especially skilled personnel, to realize its value to the business.
Figure 5: A More Realistic Profile
When evaluating appliances, there are two independent viewpoints to consider – one from the vendor's perspective and one from the customer's perspective. The responsibility of the vendor is to define clearly the purpose, design to that purpose, and deliver on specific value criteria. The responsibility of the customer is to define clearly their unique business requirements, state the required purpose of the appliance, select the best design for that purpose, and insure the expected value is realized. If the two perspectives match, a win-win situation will result. If not, there will be great frustration by one or both of the parties.
The objective of this article was to suggest evaluation criteria of appliances in the information technology field, along with an evaluation approach that displays a profile of strengths based on those criteria. Using this profile as a discussion focus, a better decision can be made as to the relevance and priority of the appliance to the requirements of the business.