For queries, supply an appropriate response from the CIP. Consider a naval UoD in which sailors are identified by a sailorNr, and ships by a shipNr, although both have names as well (not necessarily unique). List at least three different kinds of fact that are captured in this diagram. add: Student Fred is enrolled in Degree BA. Student is also compositely identified (by the time you finish the mapping, you will appreciate how much better it would be to use a studentNr instead!). Consider a conceptual schema in which the only fact type associated with Department (code) is: Department at Level {UG, PG} has students in Quantity. In schemas 1 and 2.2 we have two sets of common entities, Department and Topic-area. Assume the following conceptual schema is stored. Person Norma is a parent of Person Selena. In schema 3.1 (Figure 4.7b) we see the introduction of this generalization from Report to Publication. Each ship has a captain but some captains might not command a ship. The Employee table stores the employee number and name of each employee, the department they work for, and the year they joined the firm. Refer to the MediaSurvey conceptual schema in Figure 6.53. Such systems are often poorly documented. ), Who plays both judo and aikido? For example, a key conflict occurs if an employee's full name, employee ID number, and social security number are all assigned as keys. (Do use a join.). Indicate the CIP's response in each case. The view integration process is one of continual refinement and reevaluation. The individual end user views are represented by conceptual data models, and the integrated conceptual schema results from sufficient analysis of the end user views to resolve all differences in perspective and terminology. = employment (EA = Employed by Another; SE = Self-Employed; NE = Not Employed); Acct = accounting; NS = Non-Smoker; S = Smoker. Some degrees might not be held by any lecturer. This page was last edited on 14 June 2021, at 06:00. They can often be detected by scanning different schemas and looking for common names. These can be detected by scanning the data dictionary, if one has been established for the database. Later the subschemas are integrated or merged into a global conceptual schema that covers the whole UoD. Draw an equivalent conceptual schema diagram that does make use of nesting. Add value, set-comparison, and subtyping constraints.
This level describes the structure of the whole database for a group of users. Figures present the diagram for the entityrelationship (ER) model and show the equivalent diagram for the Unified Modeling Language (UML).
For example, in 2007, five dark green Saturn SW2s were sold. List the customerNr of each customer who has purchased a copy of all the word processors that are in stock but who has never purchased a database. Draw the conceptual fact type, and Rmap it. It is possible for two students to have the same name. The user now attempts the following sequence of updates and queries. Each credit card is used by at most two clients (e.g., husband and wife). Which schema is preferable? IDEF1X is a method for designing relational databases with a syntax designed to support the semantic constructs necessary in developing a conceptual schema. Subject enrollments are entered early in the semester, and ratings are assigned at the end of semester (so rating is optional). Rmap the Taxpayer conceptual schema for Exercise 6.5 , Question 3(b). This step is driven by the goals of completeness, minimality, and understandability. Rmap the CountryBorders conceptual schema for Exercise 7.3 , Question 5. For instance, the marketing division tends to have the whole product as a basic unit for sales, but the engineering division may concentrate on the individual parts of the whole product. add: Student Bob has MaritalStatus single. Define A B in terms of , , and projection. For each subject, we record the title and the credit. Each institution is identified by its name.
del: Student Bob has MaritalStatus single. Each degree is standardly identified by its code, but also has a unique title. Draw the conceptual schema diagram, including all uniqueness constraints. The first schema (Figure 4.4a) depicts Customer, Order, and Product as entities and places and for-a as relationships. The views are based on two separate interviews of end users. True or false? Define the natural inner join operation A B in terms of , selection, and projection. If a derived fact type should be stored, include it on the diagram with an ** mark to indicate it is both derived and stored. Let relation A have attributes x, y and relation B have attributes y, z where both y attributes are defined over the same domain. add: Person Ann programs in Language SQL. Include all constraints. Discuss the practical issues involved in making this decision. Figure 4.6. This top-down design approach may be summarized as follows: Divide the universe of discourse into manageable subareas. Hence, the IDEF1X system perspective is focused on the actual data elements in a relational database. Ignore the implicit semantic connection between Year and Date. These are consolidated into a single conceptual schema that is the superset of all of those external views. Formulate each of the following queries as a single relational algebra query. Consider the following conceptual schema. Rmap the Taxpayer conceptual schema for Exercise 6.5 , Question 3(a). Completeness requires all component concepts to appear semantically intact in the global schema. list each Person who plays Sport karatedo.
The first step is to develop a conceptual data model diagram and a set of functional dependencies (FDs) to correspond to each of the assertions given. Add mandatory role constraints, and check for logical derivations. The final schema, in Figure 4.7(c), expresses completeness because all the original concepts (report, publication, topic area, department, and contractor) are kept intact. If A is 200 10 and B is 100 5, what is the size of A B? A redundant relationship might occur between Instructor and Student. However, suppose now that while, or after, working on a project, a programmer may be promoted or even demoted in class (junior, senior). Person Terry is a parent of Person Selena.
(Do not use a join. The following information samples are extracted from a fragment of this system.
Use descriptive table and column names. Who plays both judo and aikido? In cases of rejection, supply a reason (e.g., state which part of the schema is violated). Each ship may have only one captain and vice versa. For example, sample populations from existing database tables can be used as input to the CSDP. Each lecturer has exactly one identifying name, and at most one nickname. This reengineering approach is discussed in a later chapter.
Finally, in the third case (Figure 4.4c), the relationship orders has been replaced by another relationship purchases; order-no, the identifier (key) of an order, is designated as an attribute of the relationship purchases. In other words, the concept of order has been variously represented as an entity, a relationship, and an attribute, depending on perspective. List the students who use a computer without owning one of that kind. A data structure diagram (DSD) is a data model or diagram used to describe conceptual data models by providing graphical notations which document entities and their relationships, and the constraints that bind them. Explain, with the aid of sample data, why these tables are badly designed. Let a focused query be: What is the ratio of postgraduate to undergraduate enrollments for the department of computer science? Although each student in reality has a marital status, it is optional to record it (e.g., some students may wish to keep their marital status private). In Figure 4.5(a) we have a view that focuses on reports and includes data on departments that publish the reports, topic areas in reports, and contractors for whom the reports are written. A methodology may require that each instance of a super-type may only be an instance of one sub-type. Understandability requires that the global schema make sense to the user.
List the departmental managers and the year they joined the firm. Super-type/sub-type relationships may be exclusive or not. The original ANSI four-schema architecture began with the set of external schemata that each represents one person's view of the world around him or her. For instance, if a supertype/subtype combination is defined as a result of the merging operation, the properties of the subtype can be dropped from the schema because they are automatically provided by the supertype entity. The conceptual design can then be validated and completed by communicating with a domain expert. A conceptual schema or conceptual data model is a map of concepts and their relationships used for databases. Who works for the Accounting department and started with the firm before 1970? The following table contains details on students who are to debate various religious topics. Subjects are identified by their codes. With a team of modelers, a consensus on terminology is reached, so the same names are used for the same concepts. list each Person who is a martial artist. Basically, the first three steps are concerned with identifying the fact types. Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Conceptual_schema&oldid=1028474134, Articles needing additional references from September 2014, All articles needing additional references, Articles with unsourced statements from March 2020, Creative Commons Attribution-ShareAlike License 3.0. There are three basic steps needed for conceptual schema integration: Comparison of schemas and identifying conflicts.
Underline keys and mark optional columns with square brackets. Such differences cause the conceptual models to seem to have incompatible relationships and terminology. Two subjects may have the same title.
The result is a variety of schemas. This schema applies to a one-semester period only, so we can ignore the possibility of student repeating a subject. add: Student Bob has MaritalStatus divorced. List the name of each customer who was sold at least one copy of all the spreadsheets on the stock list.
For example, we might add constraints as soon as the fact types are entered, rather than waiting for all the fact types to be entered before adding any constraints. This schedule is stored in the database (it is not computed by a formula). Some subjects might not be studied (e.g., PY205 might be a newly approved subject to be introduced in the next year). Let A have attributes x, y and B have the attribute y where both y attributes are defined over the same domain. The example given in the chapter presents a management of a large retail store who need a database to keep track of sales activities. The extract for clients 101105 is shown. In Figure 4.4, for example, an entity, a relationship, or an attribute can be used to model the concept of order in a business database. Invent some database populations that are inconsistent with the schema. View integration: type conflict: (a) schema 2.1, in which Keyword has been replaced by Topic-area and (b) schema 2.2, in which the attribute dept-name has been changed to an attribute and an entity.
Although primarily identified by its code (e.g., CS), each department also has a unique name (e.g., Computer Science) which is now mandatorily recorded. Next we look for structural conflicts between schemas. Which employees are not departmental managers? add: Student Fred is enrolled in Degree BSc.This level is concerned with providing. Premiums are determined by coverage, age, and smoking status, as shown in the following schedule. In another case, one user may view a project in terms of its goals and progress toward meeting those goals over time, but another user may view a project in terms of the resources it needs and the personnel involved. This chapter develops a global conceptual schema and a set of SQL tables for a relational database, given the requirements specification for a retail store database. As an example, the generalization of Individual over different values of the descriptor attribute job-title could represent the consolidation of two views of the databaseone based on an individual as the basic unit of personnel in the organization, and another based on the classification of individuals by job titles and special characteristics within those classifications. what Person is a grandparent of Person Selena? Nikolai Mansourov, Djenana Campara, in System Assurance, 2011. The requirements analysis should determine if there will be substantial database growth; what time frame that growth will take place over; and whether the frequency and type of queries and updates will change, as well. Perez, Sandra K., & Anthony K. Sarris, eds. If that is not semantically correct, change the names of entities so that each type of connectivity has a different set of entity names. The procedure for designing a conceptual schema small enough to manage as a single unit is referred to as the Conceptual Schema Design Procedure (CSDP).
Often all seven steps are performed for each model component as it is discussed with the domain expert, rather than applying step 1 to all components, then step 2 and so on. Rmap the conceptual schema in Figure 6.46 (absorb the subtypes before mapping). A novice designer develops a relational schema for this UoD that has the following two tables. Which females over 50 kg play judo but not karatedo? Large business domains are first divided into subareas (which may overlap). For physical design (access methods, etc.) For example, one team comprises Anne and Ernie.
Experience has shown that nearly every situation can be resolved in a meaningful way through integration techniques. Which employees worked for the firm longer than their departmental managers? (1986) to a hypothetical situation related to our example. List the codes of the subjects studied by the student(s) named Brown T. As an example of the latter case, in Figure 4.4 we see three different perspectives of the same real-life situationthe placement of an order for a certain product. C1 means that each person referred to in the database must have his/her fitness rating recorded there. Dependency conflicts result when users specify different levels of connectivity (one-to-many, etc.) When developing an information system, we first specify what is required and produce a design to meet these requirements. Then populate the tables with these data: Given this schema and database, formulate the following queries in relational algebra and state the result. Use surrogates w1, w2, for women and d1, d2, for dresses. Note:this is an informal definition of a noun concept, Definition:threaded pin that screws into a nut and is used to fasten things together, Source:New Oxford American Dictionary 2nd edition, 2005, Definition:a small ring made of metal, rubber or plastic fixed under a nut or the head of the bolt to spread the pressure when tightened or between two joining surfaces as a spacer or seal, Definition:the actuality that nut is fastened onto bolt, Note:this is an informal definition of a verb concept, Definition:the actuality that washer is fixed onto bolt, Definition:the actuality that washer1 and washer2 are fastened on the same bolt in such order that washer1 is closer to the head of the bolt than washer2, Synonymous form:washer2 is below washer1, Note:this is a definition of an individual concept, Henrik von Scheel, Ulrik Foldager, in The Complete Business Process Handbook, 2015. The set of instances of an entity class may be subdivided into entity classes in their own right. The following conceptual schema deals with applicants for positions as astronauts.
Although not shown in the schedule, age groups are identified primarily by an age group number (currently in the range 1..4). The CIP will reject a compound transaction if any of its component update operations is inconsistent with the conceptual schema. The merged schema, schema 3, is shown in Figure 4.7(a). For instance, among the attributes for the entity Product, product-number in one schema may refer to the model number and in another schema it may refer to the serial number. Rmap the Invoice conceptual schema for Exercise 6.3 , Question 3. Rmap the following conceptual schema. Similarly, a super-type/sub-type relationship may be exhaustive or not. Each car is identified by the vehicle identification number (VIN) displayed on a plate attached to the car (e.g., on its dashboard). The relational schema and a sample population for a student database are shown here. add: Student Sue has MaritalStatus single. The Department table indicates the manager and budget for each department. Map your conceptual schema to a relational schema, absorbing subtypes while maintaining subtype constraints.
Consider a UoD in which students enroll in subjects, and later obtain scores on one or more tests for each subject. The following relational schema relates to the software retailer UoD from Exercise 6.3 . These facts may also be displayed as a labeled tree (hierarchy) as shown.
For simplicity, only the latest version of the schedule is stored (a history of previous schedules is not kept).
List the computers owned (by some student) but used by no student. From time to time, this schedule may change in premiums charged, coverages offered, or even age groups. Because a conceptual schema represents the semantics of an organization, and not a database design, it may exist on various levels of abstraction. For each client a record of major illnesses (if any) is kept; one recovery figure and hospital is noted for each client illness. When this occurs, modify the keys to maintain consistency. Note that Degree is compositely identified (e.g., a Ph.D. from UCLA and a Ph.D. from MIT are treated as different degrees). Such a redundancy can be eliminated if there is a supertype/subtype relationship between Publication and Report, which does in fact occur in this case because Publication is a generalization of Report. Copyright 2022 Elsevier B.V. or its licensors or contributors. In the commercial world, there are many existing applications that have been implemented using lower level approaches, resulting in database designs that may be inconsistent, incomplete, inefficient, or difficult to maintain. Map the following conceptual schema onto a relational schema using the Rmap procedure. Constraint C1 combines two weaker constraints, since exactly one means at least one (i.e., some), and at most one. List the name and religion of all females who are not Buddhist. Map this onto a relational schema. Techniques used for view integration include abstraction, such as generalization and aggregation, to create new supertypes or subtypes, or even the introduction of new relationships. Figure 4.5(b) shows another view, with publications as the central focus and keywords on publications as the secondary data. Each captain commands a ship, and each ship has a captain. The first four fields are completed by the insurance agency and the rest by the client. add: Person David is a parent of Person David. Set out an alternative relational schema with separate tables for each node in the subtype graph. C4 means no person can be recorded as expert at more than one sport, and C5 says a person can be recorded as being an expert at a sport only if that person is also recorded as playing the same sport. The computer system has an internal clock, which may be viewed conceptually as providing an always up-to-date instance of the fact type: Date is today. Formulate the following as single queries in relational algebra. The codes y, n, PT, FT, int, and ext abbreviate yes, no, part time, full time, internal, and external. It should also be noted that minimality may not always be the most efficient way to proceed. Although the CSDP is best learned in the sequence of steps shown, in practice we might apply the steps somewhat differently. Conformation of schemas and resolving conflicts. For reasons outlined earlier, we recommend first developing this design at the conceptual level using Object-Role Modeling. List the computers used (by some student) but owned by no student. Phrase each of the following requests as a single relational algebra query. Assume that all clients have paid their 12-month fee by completing a form like that shown here (details such as name and address are omitted for this exercise). Discuss briefly how you would deal with this situation from a practical business standpoint and what changes, if any, you would suggest for the original and optimized conceptual schemas. It is exhaustive if the methodology requires that each instance of a super-type must be an instance of a sub-type. Our objective is to find meaningful ways to integrate the two views. Draw the new conceptual schema and Rmap it. Schema diversity occurs when different users or user groups develop their own unique perspectives of the world or, at least, of the enterprise to be represented in the database. As an optional exercise, map any derivation rules.
Some clients are referred by other clients (referrers) to take out a policy (this entitles referrers to special benefits outside our UoD). In a given UoD, each lecturer has at least one degree and optionally has taught at one or more institutions. For each car the dealer records the model (e.g., Saturn SW2), the year of manufacture (e.g., 2006), the retail price (e.g., $18,000), and the color (e.g., dark green).
Rmap the University schema shown. The entities as well as the key attributes may need to be renamed. The database is initially empty. Include subtype definitions and derivation rules. In later steps we add constraints to the fact types. The database is initially empty.
del: Student Sue has MaritalStatus single. Draw a conceptual schema diagram for this UoD, including uniqueness constraints, but make no use of nesting. The model does allow for what is called inheritance in object oriented terms. [citation needed] It hides the internal details of physical storage and targets on describing entities, datatypes, relationships and constraints. Applicants are given ability tests (C = Cognitive, A = Affective, P = Psychomotor) and their performance on various tasks is also measured. Throughout the procedure, checks are performed to detect derived facts and to ensure that no mistakes have been made. Draw the fact types, and apply a population check. Concepts are defined and expressed as terms and other symbols, and they are represented as vocabulary entries in SBVR Structured English. add: Person Bob is expert at Sport soccer. The resolution of these conflicts occurs in the second step: conformation of schemas. add: 3 students are enrolled in Degree BE.
List the students who own a computer but do not use a computer.
Thus, each instance of a sub-type entity class is also an instance of the entity class's super-type. for similar or even the same concepts. Structural conflicts occur in the schema structure itself. Assume questions are legal, and supply an appropriate response. Some captains might not command a ship, and some ships might not have captains. List the studentNr and degree of those students who study all the subjects listed in the database. Give the empNr, name, and year started for those managers of departments with a budget in excess of $50 000. Optimize the new conceptual schema, and Rmap it. Each instance of the super-type entity class, then is also an instance of one of the sub-type entity classes. [citation needed] It typically includes only the main concepts and the main relationships among them. The enrollment figures are now optional, but if any figures are recorded, both UG and PG figures are required. Naming conflicts include synonyms and homonyms. In practice the card type could be derived from the starting digits of the card number, but ignore this possibility for this question. Each client is identified by his/her client number (clientNr). The user now attempts the following sequence of updates and queries. List the name and gender of those who are either male Hindus or female Christians. Formulate each of the following as single queries in relational algebra. By continuing you agree to the use of cookies. View integration: the merged schema: (a) schema 3, the result of merging schema 1 and schema 2.2, (b) schema 3.1, the creation of a generalization relationship, and (c) schema 3.2, elimination of redundancy. For this UoD, students are identified by their first name. Rmap the Oz Bank conceptual schema for Exercise 6.4 , Question 6. The following table uses these abbreviations: Emp. List the students who use a computer but own no computer.
Type conflicts involve using different constructs to model the same concept. Note that a synonym exists between the entities Topic-area in schema 1 and Keyword in schema 2, even though the attributes do not match. Before we can make any meaningful statements, we need to agree on a conceptual schema that includes some noun and verb concepts as well as some individual concepts. This decision could be made during the analysis of the transactions on the database or the testing phase of the fully implemented database. The basic goal of the second step is to align or conform schemas to make them compatible for integration. What is the budget of the department in which employee 133 works? Add uniqueness constraints, and check the arity of fact types. Toby Teorey, H.V. If that person's world changes, the model must change. Records of any previous payments are outside the UoD.
Figure 4.5. One resolution of such conflicts might be to use only the most general connectivityfor example, many-to-many. Person Alice is a parent of Person Terry. add: Person Chris plays Sport karatedo. Synonyms occur when different names are given for the same concept. The third step consists of the merging and restructuring of schemas. add: Student Fred is studying Subject CS112. IDEF1X is most useful for logical database design after the information requirements are known and the decision to implement a relational database has been made. Choose suitable codes to abbreviate payment methods and card types. Assume that the Project-Programmer-Class subschema may be treated simply in snapshot fashion (i.e., only current data for these fact types are recorded). Add the uniqueness constraints to the conceptual schema diagrams for: Many manufactured products contain parts that may themselves be products of even smaller parts.
Here UG and PG abbreviate undergraduate and postgraduate, respectively. Use your schema to formulate each of the following in relational algebra. Those with differing characteristics are more difficult and, in some cases, impossible to merge. Specify a conceptual schema and relational schema for this UoD for the following cases. Person Norma is a parent of Person Paul. For each update, circle the letter if the update is accepted (based on the cumulative state of the database). The conceptual schema for a particular UoD is shown here. The relationships direct-research and advise may or may not represent the same activity or relationship, so further investigation is required to determine whether they are redundant or not. It expresses minimality because of the transformation of dept-name from an attribute in schema 1 to an entity and attribute in schema 2.2, and the merger between schema 1 and schema 2.2 to form schema 3, and because of the elimination of title as an attribute of Report and of Report relationships with Topic-area and Department. For simplicity, several data items (e.g., client's name and address) are omitted and may be ignored for this question. Figure 4.4. If the target system is not a relational system, for example, an object-oriented system, IDEF1X is not the best method. List the studentNr, name, and birth year for male students born before 1970 who obtained at least a 5 in a subject titled Databases. Specifically, it describes the things of significance to an organization (entity classes), about which it is inclined to collect information, and its characteristics (attributes) and the associations between pairs of those things of significance (relationships). Because of space limitations the dealer will never have in stock more than one car of the same model, year, and color at the same time. Jagadish, in Database Modeling and Design (Fifth Edition), 2011. The example illustrates the database life cycle steps of conceptual data modeling, global schema design, transformation to SQL tables, and normalization of those tables.
This level describes the structure of the whole database for a group of users. Figures present the diagram for the entityrelationship (ER) model and show the equivalent diagram for the Unified Modeling Language (UML).
For example, in 2007, five dark green Saturn SW2s were sold. List the customerNr of each customer who has purchased a copy of all the word processors that are in stock but who has never purchased a database. Draw the conceptual fact type, and Rmap it. It is possible for two students to have the same name. The user now attempts the following sequence of updates and queries. Each credit card is used by at most two clients (e.g., husband and wife). Which schema is preferable? IDEF1X is a method for designing relational databases with a syntax designed to support the semantic constructs necessary in developing a conceptual schema. Subject enrollments are entered early in the semester, and ratings are assigned at the end of semester (so rating is optional). Rmap the Taxpayer conceptual schema for Exercise 6.5 , Question 3(b). This step is driven by the goals of completeness, minimality, and understandability. Rmap the CountryBorders conceptual schema for Exercise 7.3 , Question 5. For instance, the marketing division tends to have the whole product as a basic unit for sales, but the engineering division may concentrate on the individual parts of the whole product. add: Student Bob has MaritalStatus single. Define A B in terms of , , and projection. For each subject, we record the title and the credit. Each institution is identified by its name.
del: Student Bob has MaritalStatus single. Each degree is standardly identified by its code, but also has a unique title. Draw the conceptual schema diagram, including all uniqueness constraints. The first schema (Figure 4.4a) depicts Customer, Order, and Product as entities and places and for-a as relationships. The views are based on two separate interviews of end users. True or false? Define the natural inner join operation A B in terms of , selection, and projection. If a derived fact type should be stored, include it on the diagram with an ** mark to indicate it is both derived and stored. Let relation A have attributes x, y and relation B have attributes y, z where both y attributes are defined over the same domain. add: Person Ann programs in Language SQL. Include all constraints. Discuss the practical issues involved in making this decision. Figure 4.6. This top-down design approach may be summarized as follows: Divide the universe of discourse into manageable subareas. Hence, the IDEF1X system perspective is focused on the actual data elements in a relational database. Ignore the implicit semantic connection between Year and Date. These are consolidated into a single conceptual schema that is the superset of all of those external views. Formulate each of the following queries as a single relational algebra query. Consider the following conceptual schema. Rmap the Taxpayer conceptual schema for Exercise 6.5 , Question 3(a). Completeness requires all component concepts to appear semantically intact in the global schema. list each Person who plays Sport karatedo.
The first step is to develop a conceptual data model diagram and a set of functional dependencies (FDs) to correspond to each of the assertions given. Add mandatory role constraints, and check for logical derivations. The final schema, in Figure 4.7(c), expresses completeness because all the original concepts (report, publication, topic area, department, and contractor) are kept intact. If A is 200 10 and B is 100 5, what is the size of A B? A redundant relationship might occur between Instructor and Student. However, suppose now that while, or after, working on a project, a programmer may be promoted or even demoted in class (junior, senior). Person Terry is a parent of Person Selena.
(Do not use a join. The following information samples are extracted from a fragment of this system.
Use descriptive table and column names. Who plays both judo and aikido? In cases of rejection, supply a reason (e.g., state which part of the schema is violated). Each ship may have only one captain and vice versa. For example, sample populations from existing database tables can be used as input to the CSDP. Each lecturer has exactly one identifying name, and at most one nickname. This reengineering approach is discussed in a later chapter.
Finally, in the third case (Figure 4.4c), the relationship orders has been replaced by another relationship purchases; order-no, the identifier (key) of an order, is designated as an attribute of the relationship purchases. In other words, the concept of order has been variously represented as an entity, a relationship, and an attribute, depending on perspective. List the students who use a computer without owning one of that kind. A data structure diagram (DSD) is a data model or diagram used to describe conceptual data models by providing graphical notations which document entities and their relationships, and the constraints that bind them. Explain, with the aid of sample data, why these tables are badly designed. Let a focused query be: What is the ratio of postgraduate to undergraduate enrollments for the department of computer science? Although each student in reality has a marital status, it is optional to record it (e.g., some students may wish to keep their marital status private). In Figure 4.5(a) we have a view that focuses on reports and includes data on departments that publish the reports, topic areas in reports, and contractors for whom the reports are written. A methodology may require that each instance of a super-type may only be an instance of one sub-type. Understandability requires that the global schema make sense to the user.
List the departmental managers and the year they joined the firm. Super-type/sub-type relationships may be exclusive or not. The original ANSI four-schema architecture began with the set of external schemata that each represents one person's view of the world around him or her. For instance, if a supertype/subtype combination is defined as a result of the merging operation, the properties of the subtype can be dropped from the schema because they are automatically provided by the supertype entity. The conceptual design can then be validated and completed by communicating with a domain expert. A conceptual schema or conceptual data model is a map of concepts and their relationships used for databases. Who works for the Accounting department and started with the firm before 1970? The following table contains details on students who are to debate various religious topics. Subjects are identified by their codes. With a team of modelers, a consensus on terminology is reached, so the same names are used for the same concepts. list each Person who is a martial artist. Basically, the first three steps are concerned with identifying the fact types. Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Conceptual_schema&oldid=1028474134, Articles needing additional references from September 2014, All articles needing additional references, Articles with unsourced statements from March 2020, Creative Commons Attribution-ShareAlike License 3.0. There are three basic steps needed for conceptual schema integration: Comparison of schemas and identifying conflicts.
Underline keys and mark optional columns with square brackets. Such differences cause the conceptual models to seem to have incompatible relationships and terminology. Two subjects may have the same title.
The result is a variety of schemas. This schema applies to a one-semester period only, so we can ignore the possibility of student repeating a subject. add: Student Bob has MaritalStatus divorced. List the name of each customer who was sold at least one copy of all the spreadsheets on the stock list.
For example, we might add constraints as soon as the fact types are entered, rather than waiting for all the fact types to be entered before adding any constraints. This schedule is stored in the database (it is not computed by a formula). Some subjects might not be studied (e.g., PY205 might be a newly approved subject to be introduced in the next year). Let A have attributes x, y and B have the attribute y where both y attributes are defined over the same domain. The example given in the chapter presents a management of a large retail store who need a database to keep track of sales activities. The extract for clients 101105 is shown. In Figure 4.4, for example, an entity, a relationship, or an attribute can be used to model the concept of order in a business database. Invent some database populations that are inconsistent with the schema. View integration: type conflict: (a) schema 2.1, in which Keyword has been replaced by Topic-area and (b) schema 2.2, in which the attribute dept-name has been changed to an attribute and an entity. Although primarily identified by its code (e.g., CS), each department also has a unique name (e.g., Computer Science) which is now mandatorily recorded. Next we look for structural conflicts between schemas. Which employees are not departmental managers? add: Student Fred is enrolled in Degree BSc.This level is concerned with providing. Premiums are determined by coverage, age, and smoking status, as shown in the following schedule. In another case, one user may view a project in terms of its goals and progress toward meeting those goals over time, but another user may view a project in terms of the resources it needs and the personnel involved. This chapter develops a global conceptual schema and a set of SQL tables for a relational database, given the requirements specification for a retail store database. As an example, the generalization of Individual over different values of the descriptor attribute job-title could represent the consolidation of two views of the databaseone based on an individual as the basic unit of personnel in the organization, and another based on the classification of individuals by job titles and special characteristics within those classifications. what Person is a grandparent of Person Selena? Nikolai Mansourov, Djenana Campara, in System Assurance, 2011. The requirements analysis should determine if there will be substantial database growth; what time frame that growth will take place over; and whether the frequency and type of queries and updates will change, as well. Perez, Sandra K., & Anthony K. Sarris, eds. If that is not semantically correct, change the names of entities so that each type of connectivity has a different set of entity names. The procedure for designing a conceptual schema small enough to manage as a single unit is referred to as the Conceptual Schema Design Procedure (CSDP).
Often all seven steps are performed for each model component as it is discussed with the domain expert, rather than applying step 1 to all components, then step 2 and so on. Rmap the conceptual schema in Figure 6.46 (absorb the subtypes before mapping). A novice designer develops a relational schema for this UoD that has the following two tables. Which females over 50 kg play judo but not karatedo? Large business domains are first divided into subareas (which may overlap). For physical design (access methods, etc.) For example, one team comprises Anne and Ernie.
Experience has shown that nearly every situation can be resolved in a meaningful way through integration techniques. Which employees worked for the firm longer than their departmental managers? (1986) to a hypothetical situation related to our example. List the codes of the subjects studied by the student(s) named Brown T. As an example of the latter case, in Figure 4.4 we see three different perspectives of the same real-life situationthe placement of an order for a certain product. C1 means that each person referred to in the database must have his/her fitness rating recorded there. Dependency conflicts result when users specify different levels of connectivity (one-to-many, etc.) When developing an information system, we first specify what is required and produce a design to meet these requirements. Then populate the tables with these data: Given this schema and database, formulate the following queries in relational algebra and state the result. Use surrogates w1, w2, for women and d1, d2, for dresses. Note:this is an informal definition of a noun concept, Definition:threaded pin that screws into a nut and is used to fasten things together, Source:New Oxford American Dictionary 2nd edition, 2005, Definition:a small ring made of metal, rubber or plastic fixed under a nut or the head of the bolt to spread the pressure when tightened or between two joining surfaces as a spacer or seal, Definition:the actuality that nut is fastened onto bolt, Note:this is an informal definition of a verb concept, Definition:the actuality that washer is fixed onto bolt, Definition:the actuality that washer1 and washer2 are fastened on the same bolt in such order that washer1 is closer to the head of the bolt than washer2, Synonymous form:washer2 is below washer1, Note:this is a definition of an individual concept, Henrik von Scheel, Ulrik Foldager, in The Complete Business Process Handbook, 2015. The set of instances of an entity class may be subdivided into entity classes in their own right. The following conceptual schema deals with applicants for positions as astronauts.
Although not shown in the schedule, age groups are identified primarily by an age group number (currently in the range 1..4). The CIP will reject a compound transaction if any of its component update operations is inconsistent with the conceptual schema. The merged schema, schema 3, is shown in Figure 4.7(a). For instance, among the attributes for the entity Product, product-number in one schema may refer to the model number and in another schema it may refer to the serial number. Rmap the Invoice conceptual schema for Exercise 6.3 , Question 3. Rmap the following conceptual schema. Similarly, a super-type/sub-type relationship may be exhaustive or not. Each car is identified by the vehicle identification number (VIN) displayed on a plate attached to the car (e.g., on its dashboard). The relational schema and a sample population for a student database are shown here. add: Student Sue has MaritalStatus single. The Department table indicates the manager and budget for each department. Map your conceptual schema to a relational schema, absorbing subtypes while maintaining subtype constraints.
Consider a UoD in which students enroll in subjects, and later obtain scores on one or more tests for each subject. The following relational schema relates to the software retailer UoD from Exercise 6.3 . These facts may also be displayed as a labeled tree (hierarchy) as shown.
For simplicity, only the latest version of the schedule is stored (a history of previous schedules is not kept). List the computers owned (by some student) but used by no student. From time to time, this schedule may change in premiums charged, coverages offered, or even age groups. Because a conceptual schema represents the semantics of an organization, and not a database design, it may exist on various levels of abstraction. For each client a record of major illnesses (if any) is kept; one recovery figure and hospital is noted for each client illness. When this occurs, modify the keys to maintain consistency. Note that Degree is compositely identified (e.g., a Ph.D. from UCLA and a Ph.D. from MIT are treated as different degrees). Such a redundancy can be eliminated if there is a supertype/subtype relationship between Publication and Report, which does in fact occur in this case because Publication is a generalization of Report. Copyright 2022 Elsevier B.V. or its licensors or contributors. In the commercial world, there are many existing applications that have been implemented using lower level approaches, resulting in database designs that may be inconsistent, incomplete, inefficient, or difficult to maintain. Map the following conceptual schema onto a relational schema using the Rmap procedure. Constraint C1 combines two weaker constraints, since exactly one means at least one (i.e., some), and at most one. List the name and religion of all females who are not Buddhist. Map this onto a relational schema. Techniques used for view integration include abstraction, such as generalization and aggregation, to create new supertypes or subtypes, or even the introduction of new relationships. Figure 4.5(b) shows another view, with publications as the central focus and keywords on publications as the secondary data. Each captain commands a ship, and each ship has a captain. The first four fields are completed by the insurance agency and the rest by the client. add: Person David is a parent of Person David. Set out an alternative relational schema with separate tables for each node in the subtype graph. C4 means no person can be recorded as expert at more than one sport, and C5 says a person can be recorded as being an expert at a sport only if that person is also recorded as playing the same sport. The computer system has an internal clock, which may be viewed conceptually as providing an always up-to-date instance of the fact type: Date is today. Formulate the following as single queries in relational algebra. The codes y, n, PT, FT, int, and ext abbreviate yes, no, part time, full time, internal, and external. It should also be noted that minimality may not always be the most efficient way to proceed. Although the CSDP is best learned in the sequence of steps shown, in practice we might apply the steps somewhat differently. Conformation of schemas and resolving conflicts. For reasons outlined earlier, we recommend first developing this design at the conceptual level using Object-Role Modeling. List the computers used (by some student) but owned by no student. Phrase each of the following requests as a single relational algebra query. Assume that all clients have paid their 12-month fee by completing a form like that shown here (details such as name and address are omitted for this exercise). Discuss briefly how you would deal with this situation from a practical business standpoint and what changes, if any, you would suggest for the original and optimized conceptual schemas. It is exhaustive if the methodology requires that each instance of a super-type must be an instance of a sub-type. Our objective is to find meaningful ways to integrate the two views. Draw the new conceptual schema and Rmap it. Schema diversity occurs when different users or user groups develop their own unique perspectives of the world or, at least, of the enterprise to be represented in the database. As an optional exercise, map any derivation rules.
Some clients are referred by other clients (referrers) to take out a policy (this entitles referrers to special benefits outside our UoD). In a given UoD, each lecturer has at least one degree and optionally has taught at one or more institutions. For each car the dealer records the model (e.g., Saturn SW2), the year of manufacture (e.g., 2006), the retail price (e.g., $18,000), and the color (e.g., dark green).
Rmap the University schema shown. The entities as well as the key attributes may need to be renamed. The database is initially empty. Include subtype definitions and derivation rules. In later steps we add constraints to the fact types. The database is initially empty.
del: Student Sue has MaritalStatus single. Draw a conceptual schema diagram for this UoD, including uniqueness constraints, but make no use of nesting. The model does allow for what is called inheritance in object oriented terms. [citation needed] It hides the internal details of physical storage and targets on describing entities, datatypes, relationships and constraints. Applicants are given ability tests (C = Cognitive, A = Affective, P = Psychomotor) and their performance on various tasks is also measured. Throughout the procedure, checks are performed to detect derived facts and to ensure that no mistakes have been made. Draw the fact types, and apply a population check. Concepts are defined and expressed as terms and other symbols, and they are represented as vocabulary entries in SBVR Structured English. add: Person Bob is expert at Sport soccer. The resolution of these conflicts occurs in the second step: conformation of schemas. add: 3 students are enrolled in Degree BE.
List the students who own a computer but do not use a computer.
Thus, each instance of a sub-type entity class is also an instance of the entity class's super-type. for similar or even the same concepts. Structural conflicts occur in the schema structure itself. Assume questions are legal, and supply an appropriate response. Some captains might not command a ship, and some ships might not have captains. List the studentNr and degree of those students who study all the subjects listed in the database. Give the empNr, name, and year started for those managers of departments with a budget in excess of $50 000. Optimize the new conceptual schema, and Rmap it. Each instance of the super-type entity class, then is also an instance of one of the sub-type entity classes. [citation needed] It typically includes only the main concepts and the main relationships among them. The enrollment figures are now optional, but if any figures are recorded, both UG and PG figures are required. Naming conflicts include synonyms and homonyms. In practice the card type could be derived from the starting digits of the card number, but ignore this possibility for this question. Each client is identified by his/her client number (clientNr). The user now attempts the following sequence of updates and queries. List the name and gender of those who are either male Hindus or female Christians. Formulate each of the following as single queries in relational algebra. By continuing you agree to the use of cookies. View integration: the merged schema: (a) schema 3, the result of merging schema 1 and schema 2.2, (b) schema 3.1, the creation of a generalization relationship, and (c) schema 3.2, elimination of redundancy. For this UoD, students are identified by their first name. Rmap the Oz Bank conceptual schema for Exercise 6.4 , Question 6. The following table uses these abbreviations: Emp. List the students who use a computer but own no computer.
Type conflicts involve using different constructs to model the same concept. Note that a synonym exists between the entities Topic-area in schema 1 and Keyword in schema 2, even though the attributes do not match. Before we can make any meaningful statements, we need to agree on a conceptual schema that includes some noun and verb concepts as well as some individual concepts. This decision could be made during the analysis of the transactions on the database or the testing phase of the fully implemented database. The basic goal of the second step is to align or conform schemas to make them compatible for integration. What is the budget of the department in which employee 133 works? Add uniqueness constraints, and check the arity of fact types. Toby Teorey, H.V. If that person's world changes, the model must change. Records of any previous payments are outside the UoD.
Figure 4.5. One resolution of such conflicts might be to use only the most general connectivityfor example, many-to-many. Person Alice is a parent of Person Terry. add: Person Chris plays Sport karatedo. Synonyms occur when different names are given for the same concept. The third step consists of the merging and restructuring of schemas. add: Student Fred is studying Subject CS112. IDEF1X is most useful for logical database design after the information requirements are known and the decision to implement a relational database has been made. Choose suitable codes to abbreviate payment methods and card types. Assume that the Project-Programmer-Class subschema may be treated simply in snapshot fashion (i.e., only current data for these fact types are recorded). Add the uniqueness constraints to the conceptual schema diagrams for: Many manufactured products contain parts that may themselves be products of even smaller parts.
Here UG and PG abbreviate undergraduate and postgraduate, respectively. Use your schema to formulate each of the following in relational algebra. Those with differing characteristics are more difficult and, in some cases, impossible to merge. Specify a conceptual schema and relational schema for this UoD for the following cases. Person Norma is a parent of Person Paul. For each update, circle the letter if the update is accepted (based on the cumulative state of the database). The conceptual schema for a particular UoD is shown here. The relationships direct-research and advise may or may not represent the same activity or relationship, so further investigation is required to determine whether they are redundant or not. It expresses minimality because of the transformation of dept-name from an attribute in schema 1 to an entity and attribute in schema 2.2, and the merger between schema 1 and schema 2.2 to form schema 3, and because of the elimination of title as an attribute of Report and of Report relationships with Topic-area and Department. For simplicity, several data items (e.g., client's name and address) are omitted and may be ignored for this question. Figure 4.4. If the target system is not a relational system, for example, an object-oriented system, IDEF1X is not the best method. List the studentNr, name, and birth year for male students born before 1970 who obtained at least a 5 in a subject titled Databases. Specifically, it describes the things of significance to an organization (entity classes), about which it is inclined to collect information, and its characteristics (attributes) and the associations between pairs of those things of significance (relationships). Because of space limitations the dealer will never have in stock more than one car of the same model, year, and color at the same time. Jagadish, in Database Modeling and Design (Fifth Edition), 2011. The example illustrates the database life cycle steps of conceptual data modeling, global schema design, transformation to SQL tables, and normalization of those tables.