03 Database Models PART2 — Transcript

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1. 0:00this is the continuation of topic three
2. 0:02which is about the evolution of data
3. 0:05models
4. 0:11we previously discussed hierarchical
5. 0:14network model
6. 0:15relational model was introduced in 1970
7. 0:18by ef
8. 0:18cod of ibm in its landmark paper
9. 0:22a relational model of data for large
10. 0:25shared data banks now we will discuss
11. 0:28entity relationship model
12. 0:30or erm which was introduced by peter
13. 0:33chen
14. 0:33in 1976 erm is the graphical
15. 0:38representation of entities and their
16. 0:39relationships in a database structure
17. 0:42quickly became popular because it
18. 0:44complemented the relational data model
19. 0:46concepts
20. 0:47the relational data model and erf
21. 0:50combine to provide
22. 0:51the foundation for tightly structured
23. 0:53database design
24. 0:55er models are normally represented in an
25. 0:58entity relationship diagram or erd
26. 1:02which uses graphical representations to
27. 1:04model database components
28. 1:07the er model is based on the following
29. 1:09components
30. 1:11entity relationship diagram or erd that
31. 1:14uses
32. 1:15graphic representations to model
33. 1:17database components
34. 1:20entity instance or entity occurrence
35. 1:23rows in the relational table
36. 1:26attributes describe particular
37. 1:28characteristics
38. 1:30and then its connectivity which is a
39. 1:32term used to label
40. 1:34the relationship types
41. 1:39figure 2.3 shows the different types of
42. 1:41relationships
43. 1:43using three er notations the original
44. 1:46shen notation the kraus foot notation in
45. 1:49the newer class diagram notation
46. 1:51which is part of the unified modeling
47. 1:54language or uml
48. 1:56the left side of the er diagram shows
49. 1:59the shen
50. 2:00notation based on peter shen's landmark
51. 2:02paper
52. 2:03in this citation the connectivities are
53. 2:06written next to each entity box
54. 2:08the relationships are represented by a
55. 2:11diamond
56. 2:12connected to the related entities
57. 2:14through a relationship
58. 2:16line the relationship name is written
59. 2:19inside the diamond
60. 2:21the middle of figure 2.3 illustrates the
61. 2:24kraus-foot notation
62. 2:26the name kraus foot is derived from the
63. 2:28three
64. 2:29prong symbol used to represent the many
65. 2:32side
66. 2:33of the relationship as you examine the
67. 2:36basic cross foot erd
68. 2:38in figure 2.3 note that the
69. 2:40connectivities are represented by
70. 2:42symbols
71. 2:43for example the 1 is represented by a
72. 2:46short line segment
73. 2:48and the m is represented by the three
74. 2:51prong
75. 2:52kraus foot in this example the
76. 2:55relationship name is written
77. 2:56above the relationship line
78. 3:00the right side of figure 2.3 shows the
79. 3:03uml notation
80. 3:05known as the uml class notation
81. 3:08note that the connectivities are
82. 3:09represented by lines with
83. 3:11symbols 1 to 1 or 1
84. 3:15to ascetics also the uml notation uses
85. 3:19names in both sides
86. 3:20of the relationship for example
87. 3:23to read the relationship between painter
88. 3:27and painting
89. 3:28note the following a painter paints one
90. 3:31too many paintings as indicated by the
91. 3:33one
92. 3:34to asterisk symbol a painting is painted
93. 3:38by one and only one painter
94. 3:40as indicated by one to one symbol
95. 3:48increasingly complex real-world problems
96. 3:50demonstrated the need for a data model
97. 3:53that more closely represented the real
98. 3:55world
99. 3:56in the object-oriented data model or
100. 3:59oodm
101. 4:00both data and its relationships are
102. 4:03contained
103. 4:04in a single structure known as an object
104. 4:06in turn
105. 4:07the oodm is the basis for the
106. 4:10object-oriented database management
107. 4:12systems
108. 4:13or oodbms
109. 4:17an oodm reflects a very different way to
110. 4:20define
111. 4:21and use entities like the relational
112. 4:23models entity
113. 4:25an object is described by its factual
114. 4:28content
115. 4:29the oodm is said to be a semantic data
116. 4:32model
117. 4:33because semantic indicates meaning
118. 4:36the oo data model based on the following
119. 4:40components
120. 4:41an object is an abstraction of a real
121. 4:45world entity in general terms an object
122. 4:48may be considered equivalent
123. 4:50to an er model's entity more precisely
124. 4:54an object represents only one occurrence
125. 4:56of an entity
126. 4:57the object semantic content is defined
127. 5:00through several of the
128. 5:02items attributes describe the properties
129. 5:06of an
130. 5:08object
131. 5:10to continue with the oodata model
132. 5:13components
133. 5:15we have class as a collection of similar
134. 5:18objects
135. 5:18with shared structure and behavior
136. 5:21organized in a class
137. 5:22hierarchy we also have class hierarchy
138. 5:25that resembles an upside down tree in
139. 5:28which
140. 5:29each class has only one period and then
141. 5:32we have inheritance
142. 5:34object inherits methods and attributes
143. 5:36of classes
144. 5:37above it unified modeling language or
145. 5:40uml describes
146. 5:42set of diagrams and symbols to
147. 5:45graphically model
148. 5:46a system
149. 5:49figure 2.4 illustrates the object
150. 5:52representation for the simple
151. 5:54invoicing problem as well as equivalent
152. 5:57uml class diagram in er model
153. 6:00the object representation is a simple
154. 6:02way to visualize a single object
155. 6:04occurrence
156. 6:06the object representation of the invoice
157. 6:08includes
158. 6:09all related objects within the same
159. 6:11object box
160. 6:13note that the connectivities 1 and
161. 6:16m or many indicate the relationship
162. 6:19of the related objects to the invoice
163. 6:22for example the one next to the customer
164. 6:26object indicates that each invoice
165. 6:29is related to only one customer the m
166. 6:33or many next to the line object
167. 6:36indicates that each invoice contains
168. 6:39many lines
169. 6:40the uml class diagram uses three
170. 6:43separate object classes customer
171. 6:47invoice and line and two relationships
172. 6:50to represent this simple
173. 6:52invoicing problem note that the
174. 6:55relationship connectivities are
175. 6:57represented by
176. 6:581 to 1 or 0 to asterisk and one to ask
177. 7:02these symbols and that the relationships
178. 7:05are name in both ends to represent
179. 7:08the different roles that the objects
180. 7:10play in the relationship
181. 7:12the er model also uses three separate
182. 7:15entities
183. 7:16and two separate representations
184. 7:19of the relationship in invoice problem
185. 7:25the evolution of dbms has always been
186. 7:29driven by the search for new ways of
187. 7:31modeling
188. 7:32and managing increasingly complex
189. 7:34real-world data
190. 7:35a summary of the most commonly
191. 7:37recognized data models is shown
192. 7:39in this figure 2.5
193. 7:42in the evolution of data models some
194. 7:44common characteristics have made them
195. 7:46widely accepted
196. 7:48a data model must show some degree of
197. 7:51conceptual simplicity
198. 7:53without compromising the semantic
199. 7:55completeness of the database
200. 7:58the model should show clarity and
201. 8:00relevance
202. 8:01a data model must represent the real
203. 8:04world as closely as possible
204. 8:07the model should be accurate and
205. 8:09complete all the needed data is included
206. 8:12and properly described representation of
207. 8:15the real world transformations or
208. 8:17behavior
209. 8:19must be in compliance with the
210. 8:20consistency
211. 8:22and integrity characteristics required
212. 8:25by the intended use
213. 8:26of the data model it is
214. 8:30important to note that not all data
215. 8:32models are created equal
216. 8:34some data models are better suited than
217. 8:37others for some tasks
218. 8:43the advantages of hierarchical model
219. 8:46includes promotes data sharing
220. 8:49parent-child relationship promotes
221. 8:51conceptual simplicity and data integrity
222. 8:54database security is provided and
223. 8:57enforced by dbms
224. 8:59efficient with one too many
225. 9:02relationships
226. 9:04while hierarchical models disadvantages
227. 9:09are requires knowledge physical data
228. 9:12storage characteristics
229. 9:14navigational system requires knowledge
230. 9:16of hierarchical path
231. 9:18changes in structure require changes
232. 9:22in all application programs
233. 9:24implementation limitations
234. 9:26no data definition and there is a lack
235. 9:29of standards
236. 9:34the network model also have advantages
237. 9:39this includes conceptual simplicity
238. 9:42handles more relationship types data
239. 9:45access is flexible
240. 9:47data owner member relationship promotes
241. 9:50data integrity
242. 9:52there is conformance to standards
243. 9:55it includes data definition language or
244. 9:58ddl
245. 9:59and data manipulation language or dml
246. 10:02while its advantages are
247. 10:06sim stem complexity limit efficiency
248. 10:10navigational system yields complex
249. 10:12implementation
250. 10:13application development and management
251. 10:16structural changes require changes
252. 10:20in all application programs
253. 10:26the relational model has advantages such
254. 10:30as structural independence is promoted
255. 10:34using independent tables tabular view
256. 10:37improves conceptual simplicity
257. 10:41ad hoc query capability is based on
258. 10:44sql isolates the end user from physical
259. 10:48level details
260. 10:50improves implementation and management
261. 10:52simplicity
262. 10:54disadvantages are requires
263. 10:58substantial hardware and system software
264. 11:01overhead
265. 11:02conceptual simplicity gives untrained
266. 11:05people the tools to use
267. 11:07a good system for lee and may promote
268. 11:10information
269. 11:12problems
270. 11:16the advantages of entity relationship
271. 11:18model includes
272. 11:20visual modeling yields conceptual
273. 11:22simplicity
274. 11:24visual representation makes it an
275. 11:26effective communication
276. 11:28tool also it is integrated with the
277. 11:32dominant relational model
278. 11:35disadvantages such as limited constrain
279. 11:38representation
280. 11:40limited relationship representation
281. 11:43no data manipulation language and the
282. 11:46loss of information content
283. 11:48occurs when attributes are removed from
284. 11:50entities to avoid crowded displays
285. 11:57the object oriented model has advantages
286. 12:00it includes semantic content is added
287. 12:04visual representation includes semantic
288. 12:07content
289. 12:08inheritance promotes data integrity
290. 12:11while disadvantages such as slow
291. 12:13development of standards
292. 12:15cost vendors to supply their own
293. 12:17enhancements
294. 12:19there is a complex navigational system
295. 12:22the learning curve is also steep and
296. 12:24high system overhead
297. 12:26slows transactions
298. 12:31nosql refers to a new generation of
299. 12:34databases that address
300. 12:36the specific challenges of the big data
301. 12:39era
302. 12:40and have the following general
303. 12:41characteristics
304. 12:43they are not based on the relational
305. 12:45model in sql
306. 12:47though the name is no sql or nosql
307. 12:51they support highly distributed database
308. 12:53architectures
309. 12:55this will be further discussed in detail
310. 12:58in later topics of our modules
311. 13:01it has different advantages
312. 13:04it has high scalability availability
313. 13:08and fault tolerance are provided uses
314. 13:12low cost commodity hardware
315. 13:14it supports big data it has key value
316. 13:18model that
317. 13:18improves storage efficiency while
318. 13:22its disadvantages are complex
319. 13:25programming is required
320. 13:27there is no relationship support no
321. 13:29transaction
322. 13:30integrity support in terms of data
323. 13:33consistency
324. 13:34it provides an eventually consistent
325. 13:37model
326. 13:40the next video presentation will discuss
327. 13:43the degrees of obstruction