The software product quality requirements and evaluation (SQuaRE) family of international standards encompasses ISO/IEC 25010, which was introduced in 2011 as a successor to ISO/IEC 9126. While ISO/IEC 9126 was technically revised and republished in 2001, it remains an international standard for specifying and evaluating SPQ [23].

The standard specifies two models: the SPQ and QIU models. The SPQ model focuses on the quality of the product and encompasses eight characteristics [24]. These characteristics are depicted in Fig. 1 (Ref. [24]), along with their corresponding sub-characteristics. Conversely, the QIU model pertains to the quality of the product when utilized by its intended users and comprises five characteristics [24]. Fig. 2 (Ref. [24]) provides an overview of the characteristics and sub-characteristics of the QIU model.

Some characteristics are further divided into sub-characteristics related to the outcomes of utilizing the product within specific contexts of use [24].

ISO 25010: A valuable framework for enterprise software teams to design and deliver successful software solutions. This standard divides SPQ into various sub-aspects, allowing developers to devise customized metrics and measurements to evaluate functional and non-functional requirements precisely [24].

ISO/IEC 25023:2016, part of the SQuaRE standard series, provides metrics for assessing the quality of systems and software products. It is based on characteristics and sub-characteristics defined in ISO/IEC 25010 [25].

To assess the SPQ, we utilized the ISO/IEC 25010 standard, requiring a thorough examination of the definitions of external SPQ characteristics and sub-characteristics. Additionally, we employed ISO/IEC 25023 in tandem with ISO/IEC 25010 to conduct a quantitative evaluation of SPQ in relation to its characteristics and sub-characteristics [24].

We have developed a checklist (as illustrated in the Appendix Table 4) to assess how each predetermined requirement influences the external sub-characteristics of the product quality model. If the variables utilized to calculate the external metric are affected by at least one requirement, it is concluded that this requirement influences the SPQ sub-characteristic.

In Step 3, we calculate the degree of impact of requirements for pregnancy monitoring, newborn care, and contraception mobile applications on the SPQ. This process entails categorizing the calculated impact degrees into three categories:

$$\mathrm{ID}(\mathrm{EC},\mathrm{B})=\frac{\sum \mathrm{ID}(\mathrm{EC},\mathrm{B})}{\mathrm{N}(\mathrm{R})}$$

This equation quantifies the degree of influence that a block of requirements (B) has on an external quality characteristic (EC), represented as ID(EC,B).

Where:

$\bullet$ N(R) represents the total number of requirements in block B.

$\mathrm{ID}(\mathrm{EC},\mathrm{R})={\displaystyle \frac{\mathrm{N}(\text{EsC,}\mathrm{R})}{\mathrm{N}(\mathrm{EsC})}}$

This formula quantifies the degree of influence that a specific requirement (R) has on an external quality characteristic (EC), referred to as ID(EC, R).

Where:

$\bullet$ N(EsC, R) represents the number of sub-characteristics of EC influenced by requirement R.

$\bullet$ N(EsC) denotes the total number of sub-characteristics of EC.

$\mathrm{ID}(\mathrm{EsC},\mathrm{B})={\displaystyle \frac{\sum \mathrm{ID}(\mathrm{EsC},\mathrm{R})}{\mathrm{N}(\mathrm{R})}}$

This equation assesses the extent to which a block of requirements (B) affects an external sub-characteristic (EsC), denoted as ID(EsC, B).

Where:

$\bullet$ N(EsC, R) denotes the number of sub-characteristics of EC influenced by requirement R.

$\bullet$ N(R) represents the total number of requirements in block B.

The values of N(R) and N(EsC) are determined using the checklist established in Step 2 (in the Appendix Table 4). Subsequently, each impact degree is categorized into one of five groups, from very high to very low, as outlined in Table 2.

An illustrative example shows the calculation of the impact degree of the postnatal mobile application features (POF) block of requirements on functional suitability (FS). This block encompasses nineteen FS requirements. Initially, the impact level of each requirement within the POF block on FS is established using the equation:

$\mathrm{ID}(\mathrm{FS},\mathrm{POF})={\displaystyle \sum _{i=1}^{i=19}}(\mathrm{ID}(\mathrm{FS},\mathrm{POFi}))/19$

Referring to the Appendix Table 4, it is observed that requirements POF6 to POF17 exclusively affect the Appropriateness sub-characteristic, with respective impact degrees of:

$\mathrm{ID}(\mathrm{FS},\mathrm{POF6})=\mathrm{ID}(\mathrm{FS},\mathrm{POF7})=\mathrm{ID}(\mathrm{FS},\mathrm{POF9})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF10})=\mathrm{ID}(\mathrm{FS},\mathrm{POF12})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF13})=\mathrm{ID}(\mathrm{FS},\mathrm{POF14})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF16})=\mathrm{ID}(\mathrm{FS},\mathrm{POF17})={\displaystyle \frac{1}{2}}$

The remaining requirements impact both the appropriateness and accuracy sub-characteristics, as indicated by the following values of impact degrees:

$\mathrm{ID}(\mathrm{FS},\mathrm{POF1})=\mathrm{ID}(\mathrm{FS},\mathrm{POF2})=\mathrm{ID}(\mathrm{FS},\mathrm{POF3})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF4})=\mathrm{ID}(\mathrm{FS},\mathrm{POF5})=\mathrm{ID}(\mathrm{FS},\mathrm{POF8})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF11})=\mathrm{ID}(\mathrm{FS},\mathrm{POF15})=\mathrm{ID}(\mathrm{FS},\mathrm{POF18})$ $=\mathrm{ID}(\mathrm{FS},\mathrm{POF19})={\displaystyle \frac{2}{2}}=1$

Thus, the overall impact degree of the entire block of POF requirements on FS is as follows:

$\mathrm{ID}(\mathrm{FS},\mathrm{POF})=(1+1+1+1+1+0.5+0.5+1+0.5+0.5+1+0.5+0.5+0.5+1+0.5+0.5+1+1)/19=0.76$

Conversely, the impact degree of the POF block on the accuracy sub-characteristic (Ac) has been calculated using the following equation:

$\mathrm{ID}(\mathrm{Ac},\mathrm{POF})={\displaystyle \sum _{i=1}^{i=19}}\mathrm{ID}(\mathrm{Ac},\mathrm{POFi})/19$

According to the checklist, all requirements affect the appropriateness sub-characteristic (Ap). Thus,

$\mathrm{ID}(\mathrm{Ac},\mathrm{POF1})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF2})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF3})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF4})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF5})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF6})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF7})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF8})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF9})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF10})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF11})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF12})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF13})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF14})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF15})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF16})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF17})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF18})=\mathrm{ID}(\mathrm{Ac},\mathrm{POF19})=1$

Therefore:

$\mathrm{ID}(\mathrm{Ac},\mathrm{POF})=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/19=1$

Referring to the classification of impact degrees shown in Table 2, it is evident that the impact of the POF requirements block on FS ID(FS, POF) is categorized as high. In contrast, the impact degree of this block on the Accuracy sub-characteristic ID(Ac, POF) is classified as very high.