Read the following article and answer the questions that follow:

Hierarchical and Relational Database Accounting Systems: Critical Aspects and Trade$-$Offs

Although the transition from hierarchical to relational databases marked a crucial turning point in the development of accounting systems, the concept hierarchy has not entirely been abandoned.

Hierarchical coding, is distinct from sequential encoding schemes, may have different implications on the selectivity$/$accuracy$/$efficiency of the $($Database Accounting System$)$ DAS.

In the late $1970$ s$,$ Codd laid down the principles of the relational model and a set of $12$ rules to be followed to achieve a relational system. That list has now been reduced to two main rules, stating that a system is relational if $(1)$ it represents data in the form of two$-$dimensional tables such as the database table and $(2)$ it supports the relational algebra functions of restrict, project, and join. With the relational model, problems like the ordering dependence, the indexing dependence and the access path dependence were resolved. After a few years, the entity$/$relationship $($E$/$R$)$ model of Chen allowed an improvement in the design and implementation of the relational model. The mathematical rigor and simplicity of these systems have long been their strong points.

The attention paid by companies to relational models has increased over time, and, consequently, many firms have moved from the hierarchical to the relational model. Today, the attention paid to the relational model design is still high, and both theoretical and practical contributions in this sense are aimed at explaining the role of data modelling for an effective relational database design.

Over the last forty years, several database systems have come onto the market, using hierarchical, network, relational, object$-$oriented, and XML data models. As the performance of relational database systems has continuously improved, the companies have felt the need to convert non$-$relational database systems into the relational, or to add a relational component to non$-$relational models.

Such change is due to the following advantages recognized in a relational accounting database system:

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Higher flexibility and data independence;

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The user$-$oriented languages Data Definition Language $($DDL$)$ and Data Manipulation Language $($DML$)$;

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Their relatively simple maintenance and physical storage conditions.

Other advantages of the relational model include minimizing data redundancy, preventing anomalies of data entry and facilitating both the updating and the deleting process.

Adapted from: Carlo Caserio, Luciano Marchi and Gabriele Pulcini. Accounting Information Systems. $2013.$

$1\mathrm{.}1$ Determine the evolution of the principles created by Codd, use relevant examples from the article. $(10)$

$1\mathrm{.}2$ With the use of relevant examples from the article examine why organisations have shifted from hierarchical to relational database. $(15)$

$1\mathrm{.}3.$ In relation to the article discuss the concept of a hierarchical database. $(10)$

$1\mathrm{.}4.$ Elaborate on each type of database language. $(15)$