## 2 Methods and Models
### Development of a Knowledge Base  
In stage 2, based on the analysis of reports, a knowledge base was developed--a summary of data in Microsoft Excel--characterizing individual construction projects. Data for each project are organized in a two-dimensional table. Each row in the table represents data for subsequent reporting periods. Each data set includes the following values: planned cost of the construction project, cumulative value of the planned cost, planned percentage of the progress of work, earned cost of the construction project, cumulative value of the earned cost, percentage of the progress of work performed, incurred cost of the construction project, cumulative value of the incurred cost, and percentage of the progress of invoiced work.  
The research assumed that the cost of a construction project is the sum of financial outlays allocated to the implementation of construction works, in particular:  
* The budgeted cost of the construction project (the cost of construction works planned before the commencement of the investment task);
* The earned cost of the construction project (the cost of actual performed construction works);
* The incurred cost of the construction project (the cost of paid construction works).  
Table 4 presents a fragment of the summary of the knowledge base for apartment houses (group A). Under the main headings in Table 4, the column number (1-7) has been added as an auxiliary number, along with the determination of the relationship between the data contained in the table (for columns 4 and 7).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Investment**} & **Scheduled** & **Actual** & **Scheduled** & **Budgeted Cost** & **Inverted Cost** & **Budgeted/Inverted Cost** \\  & **Time** & **Time** & **Time/Actual Time** & **Budgeted Cost** & **Inverted Cost** & **Cost** \\ \hline
1 & 2 & 3 & 4 = 2/3 & 5 & 6 & 7 = 5/6 \\ \hline _A.1_ & 13 & 16 & 1.23 & 17,002,557.00 & 17,002,557.00 & 1.00 \\ _A.2_ & 14 & 16 & 1.14 & 12,580,200.00 & 12,580,200.00 & 1.00 \\ _A.3_ & 14 & 16 & 1.14 & 15,231,003.00 & 15,231,003.00 & 1.00 \\ _..._ &... &... &... &... &... &... \\ _B.1_ & 21 & 30 & 1.43 & 54,136,619.00 & 54,136,619.00 & 1.00 \\ _B.2_ & 15 & 27 & 1.80 & 23,284,800.00 & 23,284,800.00 & 1.00 \\ _B.3_ & 19 & 23 & 1.21 & 24,553,200.00 & 24,553,200.00 & 1.00 \\ _..._ &... &... &... &... &... &... \\ _C.1_ & 22 & 34 & 1.55. & 42,313,695.00 & 58,646,384.15 & 1.39 \\ _C.2_ & 15 & 17 & 1.13 & 14,670,506.00 & 15,811,877.84 & 1.08 \\ _C.3_ & 14 & 16 & 1.14 & 18,772,396.15 & 22,234,333.17 & 1.18 \\ _..._ &... &... &... &... &... &... \\ _D.1_ & 13 & 15 & 1.15 & 135,000,00.00 & 157,112,077.84 & 1.16 \\ _D.2_ & 10 & 13 & 1.30 & 65,000,000.00 & 65,000,000.00 & 1.00 \\ _D.3_ & 10 & 11 & 1.10 & 16,000,000.00 & 16,708,000.00 & 1.04 \\ _..._ &... &... &... &... &... &... \\ _E.1_ & 6 & 8 & 1.33 & 3,539,000.00 & 3,586,422.60 & 1.01 \\ _E.2_ & 6 & 8 & 1.33 & 8,795,000.00 & 8,988,911.20 & 1.02 \\ _..._ &... &... &... &... &... &... \\ _F.1_ & 10 & 13 & 1.30 & 7,870,000.00 & 7,895,911.00 & 1.01 \\ _..._ &... &... &... &... &... &... \\ G.1 & 24 & 25 & 1.04 & 86,902,405.00 & 89,191,782.66 & 1.03 \\ _..._ &... &... &... &... &... &... \\ H.1 & 9 & 10 & 1.11 & 11,550,865.65 & 11,786,564.80 & 1.02 \\ _..._ &... &... &... &... &... &... \\ I.1 & 11 & 26 & 2.36 & 89,148,640.24 & 123,139,268.70 & 1.38 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Fragment of the knowledge base.  
In the knowledge base and in the table in column 1, the method of coding construction projects adopted in the research is presented: \(X.Y\), where:  
\(X\)--symbol of a category/group of building objects (A-I), according to Table 1;  
\(Y\)--number of the analyzed construction projects (1-14), according to Table 1.