i have a complicated exercise please help to get some points about the entity and their props, whats their assocs, and cardinality EX: Any point of the earth surface is characterized by its geographical coordinates and who are expressed compared to ellipsoids which models the form of earth (example Clarke 1880). Each ellipsoid is charactirized by its half large axis A , its small half small axis B and its factor of flattens F= (a-b)/a. altitudes are expressed compared to geoid . The planimetric coordinates are obtained by projection of the ellipsoid on a cylindrical , conical suface or planes, each one define a projection system. We want to create a database to manage different kind of coordinates and systems . Create The CDM ?????
Thanks 4 replying :) CDM = Conceptual Data Model ... yup it's a homework i have a course in foundamental of DBMS and am not pro cuz its the beginning , i want an idea like Entity 1 is : point > Identifier 1 is geographical coordinates > attribute 1 is which model . something like that so i want to make a CDM for this information i hope u got it :) thanks again
We don't do homework here. I don't need a qualification in fundamentals of Database Management Systems and you learn nothing if I give you the answer.
Show us what you've done so far, explain where you're stuck and we'll offer advice. We will not do your work for you. If you don't know where to start or are completely lost, go speak to your course instructor.
i didn't say do my homework i said any ideas ? about my stuck i said i just need more entities but i can't find so what i need is just a push 2 complete this exercise anyway Thank you for your understanding :)
The only idea I have is that I need a lot more information about what you're trying to do and what you've already done before I can say anything reasonable or useful.
List the entities and attributes that you've already identified and explain what you think is missing.
( The only idea I have... etc ) < this is what i was waiting for. really thanks for your time ... but i have a question : do you think my list was correct i mean this one : Entity 1 is : point > Identifier 1 is geographical coordinates > attribute 1 is which model _____ |Point|<--- this is the Entity ------- geographical| coordinates |<--- this is the Identifier ----------- |model|<---- this is Attribute or Properties
We want to create a database to manage different kind of coordinates and systems.. it's just an example so it's not very detailed ... i mean don't look accurately you know we've studied that there are 4 rules to make a CDM : 1- Every entity must have one Identifier 2- Every property have to be functional and directly dependent of the identifier 3- Every attribute have to be appear one time in all CDM 4- Calculated fields most not exists in the CDM
i confused please help !!!
Posted - 10/14/2010 : 13:53:18
