# Development of a Framework to Understand Tables in Engineering Specification Documents
## 1 Introduction  
Engineers create and exchange engineering specification documents to develop a product. One of the efficient ways of representing product specification in engineering specification documents is a table. A table is a physical and logical representation to organize structured data [1]. Tables in documents provide a compact method for presenting relational information in an immediate and intuitive manner, while simultaneously organizing and indexing the information. In the case of engineering specification documents, tables are frequently used to represent an organized product specification explicitly. Table format for product specification helps engineers to understand the meaning of the product specification quickly. Generally, tables are designed in so many graphically different ways such as simple hierarchies of strings, relational structures like database tables, or any combinations of them. This paper only focused on tables which are structured for product specification, so that they must have graphical lines to represent cells in a table and each cell has only one content. Figures 1 and 2 are table examples illustrating the restricted table forms. They have horizontal and vertical lines, and they present a set of relations holding between hierarchical concepts for product specifications. The table in Figure 1 has nested multiple rows of column headers (labels) to explain the meanings of data in numbers. As shown in the title of the table in Figure 1, the table explains speed rating of two different pumps with different ranges of stroke length. The data in the table shows speed rating in two different units; rpm and m/s. Engineers can easily understand the table by recognizing the structure of the table and by catching the meaning of terms in the table. Figure 2 shows a table example in an engineering specification drawing. Tables in engineering drawings include meta-information of drawings such as drawing version, people involved in the drawing, related project information, and so on. Tables in an engineering specification drawing are fitted into one big rectangle to minimize the size of tables. Engineers can classify different information in the big rectangle by separating sub-tables \begin{table}
\begin{tabular}{|c|c|c|c|c|} \hline \multicolumn{2}{|c|}{} & \multicolumn{2}{|c|}{Speed rating} \\ \hline Stroke & \multicolumn{2}{|c|}{Single-acting} & \multicolumn{2}{|c|}{Double-acting} \\ length & \multicolumn{2}{|c|}{plunger-type pumps} & \multicolumn{2}{|c|}{piston-type pumps} \\ \hline mm & rpm & m/s & rpm & m/s \\ \hline
50 & 375 & 0.62 & 70 & 0.12 \\ \hline
75 & 265 & 0.66 & - & - \\ \hline
100 & 210 & 0.70 & 58 & 0.19 \\ \hline
125 & 180 & 0.75 & - & - \\ \hline
150 & 155 & 0.77 & 50 & 0.25 \\ \hline
175 & 145 & 0.84 & - & - \\ \hline
200 & 130 & 0.86 & - & - \\ \hline
250 & - & - & 42 & 0.35 \\ \hline
300 & - & - & 39 & 0.39 \\ \hline
350 & - & - & 37 & 0.43 \\ \hline
400 & - & - & 35 & 0.46 \\ \hline \end{tabular}
\end{table} 
Table 1 MAXIMUM ALLOWABLE SPEED RATINGS FOR POWER PUMPS IN CONTINUOUS SERVICE  
Figure 1: A table example in an engineering specification document. Figure 2: A table example in an engineering specification drawing. with geometric line and space patterns. Then, engineers can understand each sub-table as they did for the table in Figure 1.  
Keyword-based search is frequently used by engineers to find product specification. Although engineers may obtain data they are looking for, the keyword-based search technique has two issues. First, it may return the overload search results. The overload results require engineers to spend more time on information acquisition. Second, if computers could not establish correct relationships among the searching keywords, they cannot return the specification engineers want. The problems are a consequence of the inability of the machine to capture the logical representation of tables in engineering specification documents.