Talk:Logical schema
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Merge Logical schema and Semantic data model here
I like to propose to merge Logical schema and Semantic data model here. This seems to be three alternative terms for one and the same thing. -- Marcel Douwe Dekker (talk) 21:23, 15 October 2008 (UTC)
- I guess this isn't a good idea after all. -- Marcel Douwe Dekker (talk) 22:26, 27 November 2008 (UTC)
Remove references to XML
The claim that "Currently, the choices [of a logical schema] are relational, object-oriented, and XML" is incorrect. XML is a coding method rather than a type of schema. Any type of logical schema could be represented in XML. I will reword this section soon unless people comment here about why I shouldn't. Matthew C. Clarke 03:41, 31 October 2009 (UTC)
- I've now done this Matthew C. Clarke 21:41, 4 November 2009 (UTC)
Move comparison of conceptual, logical & physical data model to Data modeling
Data modeling gives an overview of those three, so the compariso table would fit better there Dobinator (talk) 16:39, 11 January 2019 (UTC)
External link dead
anyone able to replace this? site seems dead, thanks 86.158.66.129 (talk) 00:06, 8 December 2009 (UTC)
Dependant or independant from data management technology ?
The article recently moves from
"A logical data model (LDM) in systems engineering is a representation of an organization's data, organized in terms of a particular data management technology."
to
"A logical data model (LDM) in systems engineering is a representation of an organization's data, organized in terms entities and relationships and is independent of any particular data management technology."
Why ? Does it mean that the LDM representation should stay the same for a relational database, a OLAP cube or an XML file/stream,... ? I'm not sure.
I have, at the moment, a lot of disucussions around this topic and everyone seems to have a different opinion. What are yours ?
Noomdas (talk) 15:33, 18 December 2009 (UTC)
Yes, the CDM and LDM are independent of any particular data management technology, such as Oracle or MySql database table schema. That is why the Physical DM is different, to provide the data management-specific info, like field format and index-key identification. — Preceding unsigned comment added by Kitdaddio (talk • contribs) 15:25, 20 March 2013 (UTC)
- I think the statement is unclear and confuses "specific data mangement technology" with "specific data management product". The technology might be RDBMS, object databases, XML files, etc. The product can be Oracle, MySql, etc. The following quotes are from articles that all agree on the difference between conceptual and logical data models:
- Template:Quote
- Template:Quote
- Template:Quote
- The current article states different things, both which I think are unclear or wrong:
- Template:Quote
- Template:Quote
- I think the other articles are correct and that the change made is incorrect. This error is also reflected in https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model which, unclearly/erroneously states "The logical ER model is however developed independent of technology into which it will be implemented.".
- My suggestions:
- Template:Quote
- Template:Quote
- Do you agree?
Conceptual v Logical v Physical
Logical data models are typically developed for a specific application (e.g. Sales system, data warehouse), though the technology has not been chosen. For the former, operational system, you would normalise (typically to 4NF), but the BI manager would have screaming hab-dabs if you proposed anything other than a star schema for the data warehouse. As the logical model contains primary & secondary keys and relationships, surely you would also produce the logical model as either 4NF or star schema as appropriate the the business use of the application? MaryEFreeman (talk)
The article states that the LDM "Is normalized to fourth normal form (4NF)". That seems completely out of place since an LDM may not even be relational (could be ER, UML or some other). LDM is still an LDM whether it satisfies 1NF, 6NF or no NF at all. Oradium (talk) 16:21, 28 September 2019 (UTC)
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