INFS1603 Lecture Notes - Lecture 2: Application Programming Interface, Ibm Mainframe, Data Modeling
2 Sep 2018
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Document Summary
Data modelling: process of creating a specific data model for a determined problem domain. Problem domain: a clearly defined area within the real-world environment, with a well-defined scope and boundaries that will be systematically addressed. Data model: a relatively simple representation, usually graphical, of a more complex real-world data structure. Hierarchical dbms: basic logical structure represented by an upside-down tree which contains levels or segments. A seg(cid:373)e(cid:374)t is the e(cid:395)ui(cid:448)ale(cid:374)t of a file s(cid:455)ste(cid:373)(cid:859)s (cid:396)e(cid:272)o(cid:396)d t(cid:455)pe. The highe(cid:396) la(cid:455)e(cid:396) is pe(cid:396)(cid:272)ei(cid:448)ed as the parent of the segment, and beneath it is the child. Depicts 1:m relationships therefore each can have many children by only one parent. 1:m promotes data integrity: data retrieval can be fast, high security. Disadvantages: hierarchical cannot support m:n relationships, data redundancy, no data definition or manipulation language. Network dbms: represents complex data relationships more effectively than the hierarchical model. It is a collection of records in m:n relationships.
