Mastering Data Warehouse DesignRelational and Dimensional Techniques phần 3 ppsx

Introductions. The participants introduce themselves, and the session objectives are reviewed. Education. Education is provided on the relevant concepts, on the process, and on the starter model. Review and refinement of subject areas. The subject areas in the starter model are reviewed, and a set of subject areas is derived. Definitions for those subject areas are then reviewed and refined. Refinement. The list of potential subject areas is reviewed and refined to arrive at the set of subject areas. A critical part of the agenda for the first session is education. During the edu- cational portion of the meeting, the facilitator explains what a subject area is, how it should be identified and defined, and why the resultant model is bene- ficial. The processes (for example, brainstorming) to be employed are also described along with the rules for the facilitated session. TIP If some members of the group understand the concepts and others don’t, consider having an educational session before the actual facilitated session. This provides the attendees with a choice and does not force people who know the topic to attend redundant education. The remainder of this section presumes that the group is not beginning with a starter model. Following the educational session, the group engages in a brainstorming ses- sion to identify potential subject areas. In a brainstorming session, all contri- butions are recorded, without any discussion. It is, therefore, not uncommon for people to identify reports, processes, functions, entities, attributes, organi- zations, and so on, in addition to real subject areas. Figure 3.1 shows the poten- tial result of such a brainstorming session for an automobile manufacturer such as the Zenith Automobile Company. If you look closely at the flip charts, you’ll see that most of the second sheet and part of the third sheet deviated into too great a level of detail. When this happens, the facilitator should remind the group of the definition of a subject area. Understanding the Business Model 73 Figure 3.1 Result of brainstorming session. The next step in the process is to examine the contributed items and exclude items that are not potential subject areas. Each item is discussed and, if it does not conform to the definition of a potential subject area, it is removed and pos- sibly replaced by something that conveys the concept and could conform to the definition of a subject area. When this process is over, there will be fewer subject areas on the list, as shown in Figure 3.2. Some of the transformation actions that took place follow: ■■ ITEMS and PRODUCTS were determined to be the same thing and AUTOMOBILES was selected as the term to be used since all the products and items were driven by the automobiles. Further, these were found to encompass CARS, PAINT, LUXURY CAR, PARTS, PACKAGES, MOTORS, USED CARS. ■■ CUSTOMER and CONSUMER were determined to be the same thing and CUSTOMERS was selected as the term to be used. PROSPECTS was absorbed into this area. ■■ VARIANCE REPORT and SALES ANALYSIS REPORT were determined to be reports and eliminated. POTENTIAL SUBJECT AREAS - PAGE 1 • CUSTOMERS • PRODUCTS • CARS • DEALERS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE POTENTIAL SUBJECT AREAS - PAGE 2 • SALES ORDER • CASH REGISTER • SALES REGION • DELIVERY TRUCK • EMPLOYEES • COMPETITORS • REGULATORS • GENERAL LEDGER • CREDIT CARD • LOAN • PROMOTIONS POTENTIAL SUBJECT AREAS - PAGE 3 • ADVERTISEMENT • CONTRACTOR • WARRANTY • SERVICE POLICY • SALES TRANSACTIONS • SUPPLIER • MANUFACTURERS • PARTS • PACKAGES • LOANER CARS • SALES ANALYSIS RPT POTENTIAL SUBJECT AREAS - PAGE 4 • PROSPECTS • ITEMS • MOTORS • USED CARS • WASTE • SUPPLIES • DEALER Chapter 3 74 ■■ MARKETING was determined to be a function and was eliminated. During the discussion, ADVERTISEMENTS and PROMOTIONS were added. ■■ CREDIT CARD and LOAN were grouped into PAYMENT METHODS. ■■ EMPLOYEES and CONTRACTOR were combined into HUMAN RESOURCES. ■■ DEALERSHIPS and DEALERS were deemed to be the same, and DEALERS was chosen as the subject area. The resultant list should consist solely of data groupings, but some may be more significant than others. Next, the group is asked to look at the list and try to group items together. For example, WAREHOUSES, DISTRIBUTION CEN- TERS, and FACTORIES are shown in Figure 3.2. WAREHOUSES and DISTRI- BUTION CENTERS could be grouped into a potential subject area of FACILITIES, with FACTORIES also established as a subject area. When this process is over, the most likely candidates for the subject areas will have been identified, as shown in Figure 3.3. Figure 3.2 Result of refinement process. POTENTIAL SUBJECT AREAS - PAGE 1 • CUSTOMERS • PRODUCTS • CARS • DEALERSHIPS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE POTENTIAL SUBJECT AREAS - PAGE 2 • SALES ORDER • CASH REGISTER • SALES REGION • DELIVERY TRUCK • EMPLOYEES • COMPETITORS • FACTORY • GENERAL LEDGER • CREDIT CARD • LOAN • SHOWROOM POTENTIAL SUBJECT AREAS - PAGE 3 • LUXURY CAR • CONTRACTOR • WARRANTY • SERVICE POLICY • SALES TRANSACTION • SUPPLIER • MANUFACTURERS • PARTS • PACKAGES • LOANER CARS • SALES ANALYSIS RPT POTENTIAL SUBJECT AREAS - PAGE 4 • PROSPECTS • ITEMS • MOTORS • USED CARS • WASTE • SUPPLIES • DEALER • ADVERTISEMENTS • PROMOTIONS • PAYMENT METHODS • HUMAN RESOURCES Understanding the Business Model 75 Figure 3.3 Result of reduction process. This virtually completes the first facilitated session. In preparation for the next session, each subject area should be assigned to two people. Each of these peo- ple should draft a definition for the subject area and should identify at least three entities that would be included within it. (Some people may be responsible for more than one subject area.) The work should be completed shortly following the meeting and submitted to the facilitator. The group should be advised that on the intervening day, the facilitator uses this information and information from subject area model templates (if available) to provide a starting point for the second session. Consolidation and Preparation for Second Facilitated Session During the period (potentially as little as one day) between the two facilitated sessions, the facilitator reviews the definitions and sample entities and uses these to create the defined list of subject areas that will be used in the second facilitated session. The facilitator should create a document that shows the contributions provided, along with a recommendation. For example, for the subject area of Customers, the following contributions could have been made: Contribution 1. “Customers are people who buy or are considering buying our items.” Sample entities are Customer, Wholesaler, and Prospect. Contribution 2. “Customers are organizations that acquire our items for their internal consumption.” Sample entities are Customer, Customer Sub- sidiary, and Purchasing Agent. POTENTIAL SUBJECT AREAS - PAGE 4 • CUSTOMERS • PRODUCTS • CARS • DEALERSHIPS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE POTENTIAL SUBJECT AREAS - PAGE 3 • CUSTOMERS • PRODUCTS • CARS • DEALERSHIPS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE POTENTIAL SUBJECT AREAS - SUMMARY • CUSTOMERS • DEALERSHIPS • FACILITIES • SALES • EQUIPMENT • EXTERNAL ORGS • FINANCIALS • SUPPLIERS • PRODUCTS • INCENTIVE PROGRAMS • HUMAN RESOURCES • SALES ORGS POTENTIAL SUBJECT AREAS - PAGE 2 • CUSTOMERS • PRODUCTS • CARS • DEALERSHIPS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE POTENTIAL SUBJECT AREAS - PAGE 1 • CUSTOMERS • PRODUCTS • CARS • DEALERSHIPS • WAREHOUSES • DISTRIBUTION CTRS • CONSUMER • PAINT • VARIANCE REPORT • MARKETING • DISPLAY CASE Chapter 3 76 The subject area template information (previously shown in Table 3.3) pro- vides a definition of Customers as “People and organizations who acquire and/or use the company’s products,” and provides Customer, Prospect, and Consumer as sample entities. Using this information, the facilitator could include the information for CUSTOMERS shown in Table 3.5. Similar informa- tion would be provided for each of the subject areas. Second Facilitated Session The agenda for the second session should include the following items: Review. The results of the first session and the work performed since then are reviewed. Refinement. The subject areas and their definitions are reviewed and refined. Relationships. Major relationships between pairs of subject areas are created. Conclusion. The model is reviewed, unresolved issues are discussed, and follow-up actions are defined. Table 3.5 Potential Subject Area: CUSTOMER POTENTIAL RECOMMENDED SAMPLE DEFINITIONS DEFINITION ENTITIES COMMENTS •Customers are People or •Consumer •Some customers lease people who buy organizations •Customer our items, hence or are considering who acquire the •Customer acquire is more buying our Company’s items Purchasing appropriate than buy. products. Agent •“Considering buying” •Customers are •Prospect is left out since all organizations definitions imply past, that acquire our present, and future. items for their •Customer Purchasing internal Agent is not used since consumption. this is part of Human •People and Resources. organizations who acquire and/or use the company’s products Understanding the Business Model 77 The success of the second session is highly dependent on each of the partici- pants completing his or her assignment on time and on the facilitator compiling a document that reflects the input received and best practices. A limit should be placed on the discussion time for each subject area. If the subject area is not resolved by the end of the allotted time, the responsibility to complete the remaining work should be assigned to a member of the team. Often, the remaining work will consist of refining the wording (but not the meaning) of the definition. After all of the subject areas have been discussed, the major relationships among the subject areas are identified and the resultant subject area diagram is drawn. This step is the least critical one in the process because the subject area relationships can be derived naturally from the business data model as it is developed. A critical final step of the second facilitated session is the devel- opment of the issues list and action plan. Follow-on Work The issues list and action plan are important products of the second facilitated session, since they provide a means of ensuring that the follow-on work is completed. The issues list contains questions that were raised during the ses- sion that need to be resolved. Each item should include the name of the person responsible and the due date. The action plan summarizes the remaining steps for the subject area model. Often, the product of the session can be applied immediately to support development of the business data model, with refine- ments being completed over time based on their priority. Subject Area Model Benefits Regardless of how quickly the subject area model can be developed, the effort should be undertaken only if there are benefits to be gained. Three major ben- efits were cited in Chapter 2: ■■ The subject area model guides the business data model development. ■■ It influences data warehouse project selection. ■■ It guides data warehouse development projects. The subject area model is a tool that helps the modeler organize his or her work and helps multiple teams working on data warehouse projects recognize areas of overlap. The sidebar shows how the subject area model can be used to assist in data warehouse project definition and selection. Chapter 3 78 Subject Area Model for Zenith Automobile Company A potential subject area model for the Zenith Automobile Company is pro- vided in Figure 3.5. Only the subject areas needed to answer the business ques- tions and Customers are shown. Understanding the Business Model 79 Data Warehouse Project Definition and Selection Figure 3.4 shows the primary subject areas that are needed to answer the busi- ness questions for the Zenith Automobile Company. Figure 3.4 Mapping requirements to subject areas. Using the information in Figure 3.4, a logical implementation sequence would be to develop the Automobiles, Dealers, and Sales Organizations subject areas first since virtually all the questions are dependent on them. Factories or Incen- tive Programs could be developed next, followed by the remaining one of those two. For the business questions posed, no information about Customers and Sup- pliers is needed. Even if the business considered question 3 or 7 to be the most significant, they should not be addressed first. The reason for this conclusion is that in order to answer those questions, you still need information for the other three subject areas. This is an example of the iterative development approach whereby the data warehouse is built in increments, with an eye toward the final deliverable. QUESTION 1 AUTO- MOBILES CUSTOMERS DEALERS SUBJECT AREA FACTORIES INCENTIVE PROGRAMS SALES ORGS 2 3 4 5 6 7 8 9 10 11 Figure 3.5 Zenith Automobile Company partial subject area. Definitions for each subject area follow: ■■ Automobiles are the vehicles and associated parts manufactured by Zenith Automobile Company and sold through its dealers. ■■ Customers are the parties that acquire automobiles and associated parts from Dealers. ■■ Dealers are agencies authorized to sell Zenith Automobile Company automobiles and associated parts. ■■ Factories are the facilities in which Zenith Automobile Company manufac- tures its automobiles and parts. ■■ Incentive Programs are financial considerations designed to foster the sale of automobiles. ■■ Sales Organizations are the groupings of Dealers for which information is of interest. Figure 3.6 provides a potential subject area model for a retail company. This model is provided as a reference point for some of the case studies used in Chapters 5–8. DEALERS AUTOMOBILES CUSTOMERS FACTORIES INCENTIVE PROGRAMS SALES ORGANIZATIONS Chapter 3 80 Figure 3.6 Retail subject area model starter. Sample definitions for each of the subject areas follow. ■■ Communications are messages and the media used to transmit the messages. ■■ Customers are people and organizations who acquire and/or use the company’s items. ■■ Equipment is movable machinery, devices, and tools and their integrated components. ■■ Human Resources are individuals who perform work for the company. ■■ Financials is information about money that is received, retained, expended, or tracked by the company. ■■ Internal Organizations are formal and informal groups to which Human Resources belong. ■■ Items are goods and services that the company or its competitors provide or make available to Customers. ITEMS CUSTOMERS SALES STORES VENDORS FINANCIALS OTHER FACILITIES LOCATIONS EQUIPMENT INTERNAL ORGANIZATIONS HUMAN RESOURCES COMMUNICATIONS Understanding the Business Model 81 ■■ Locations are geographic points and areas. ■■ Other Facilities are real estate and other structures and their integrated components, except stores. ■■ Sales are transactions that shift the ownership or control of an item from the Company to a Customer. ■■ Stores are places, including kiosks, at which Sales take place. ■■ Vendors are legal entities that manufacture or provide the company with items. Business Data Model As we explained in Chapter 2, a model is an abstraction or representation of a subject that looks or behaves like all or part of the original. The business data model is one type of model, and it is an abstraction or representation of the data in a given business environment. It helps people envision how the infor- mation in the business relates to other information in the business (“how the parts fit together”). Products that apply the business data model include appli- cation systems, the data warehouse, and data mart databases. In addition, the model provides the meta data (or information about the data) for these data- bases to help people understand how to use or apply the final product. The subject area model provides the foundation for the business data model, and that model reduces the development risk by ensuring that the application sys- tem correctly reflects the business environment. Business Data Development Process If a business data model does not exist, as is assumed in this section, then a portion of it should be developed prior to embarking on the data warehouse data model development. The process for developing the business data model cannot be described without first defining the participants. In the ideal world, the data stewards and the data modelers develop the business data model jointly. Most companies do not have formal data stewardship programs, and the busi- ness community (and sometimes the information technology community) may not see any value in developing the business data model. After all, it delays producing the code! The benefits of the business data model were pre- sented in Chapter 2, but in the absence of formal data stewards, the data mod- eler needs to identify the key business representatives with the necessary knowledge and the authority to make decisions concerning the data defini- tions and relationships. These are often called “subject matter experts” or Chapter 3 82 [...]... facilitate creation of data marts that need cross-tab analysis, and data is segregated based on stability (to reduce the number of rows added to the data warehouse) and usage (to reduce the need to join data to satisfy queries These steps help organize the data to meet performance objectives in loading data into the data warehouse, minimizing storage requirements, and delivering the data to the data marts Once... business data model and applies eight steps to arrive at a model that is optimized to meet the objectives of the data warehouse The specific information requirements will be identified, and these will be used as the basis for developing the data warehouse model Some of the issues to be addressed include selecting the data elements of interest, handling historical requirements, ensuring data consistency, and. .. design of the data warehouse reflect its primary mission, which is to serve as a collection point for the needed data stored in various operational systems and as a distribution point for sending this data to the data marts The major factors affecting the content of the data warehouse are the information needs of the people who will use the resultant data marts and the organization of the data in the... and partitioning may also be applied Step 1: Select the Data of Interest The first step in developing the data warehouse is to select the data of interest There are two major reasons for making this the first step First, it places the purpose and business objectives of the data warehouse project in the foreground All decisions made concerning the data warehouse model consider the business purpose and. .. deleterious effect on the data marts already in production The data warehouse model, and hence in the physical data warehouse, will evolve as additional needs are discovered Since the business community is not directly accessing the data, changes in the data warehouse can be made without affecting users who do not need the changed data, as shown in Figure 4.1 Figure 4.1 Benefit of data segregation Dealer... prototypes, existing reports and queries, and the system or physical models of the systems expected to be sources to the data warehouse The modeler needs to recognize that despite best intentions, not all of the information requirements can be defined in advance One of the advantages using a relational model for the data warehouse and of segregating the data warehouse from the data marts is that this facilitates... facilitate data delivery to the data marts Some additional changes to improve the performance of the model are then provided Methodology The data warehouse system data model is developed by applying an eightstep transformation process to the business data model The eight steps are: 1 Select the data of interest 2 Add time to the key 3 Add derived data 4 Determine granularity level 5 Summarize data 6 Merge... possibly thousands, of data elements The development team needs to quickly cull the elements to only those that must be included in this iteration of the data warehouse When a business data model does not exist and the development team creates the business data model for the scope of the project, virtually all of the elements in that model are included in the data warehouse model Since only the data elements... not the best structure for the data warehouse Using the third normal form model for the data warehouse is analogous to selecting any screwdriver for the job Just as the screwdriver should be based on the size of the screw being driven, the third normal form model needs to be adjusted to meet the data warehouse needs The business scenario used to develop the data warehouse data model is the Zenith Automobile... used to name and define entities and attributes Table 3. 6 presents the results of this activity for the entities of interest for the business questions that need to be answered 86 Chapter 3 Entity- and Attribute-Modeling Conventions The rules for naming and defining entities and attributes should be established within each enterprise Entities and attributes represent business-oriented views, and the naming . business data model include appli- cation systems, the data warehouse, and data mart databases. In addition, the model provides the meta data (or information about the data) for these data- bases. needed to answer the business ques- tions and Customers are shown. Understanding the Business Model 79 Data Warehouse Project Definition and Selection Figure 3. 4 shows the primary subject areas that. CASE Chapter 3 76 The subject area template information (previously shown in Table 3. 3) pro- vides a definition of Customers as “People and organizations who acquire and/ or use the company’s products,” and