4. Defining data model Items

the purpose of the sheet items is to define the items, which includes their name, data type and if they are an identifier, as well as their place in the data model hierarchy note the sequence of steps shown in this guide is a recommendation, as it felt the most natural for the author but users are free to follow their own preferred sequence defining the item names items are the part of a data model which provides a meaning and context to a value and make it possible for users to understand what the recorded value means users will define the names for these items in the column labeled item name the users enters the name into the next empty cell in this column important do not leave blank rows between entries or at the start a blank row will be seen as the end of the configuration and the configurator will not process any entry past the blank row the configurator will verify the item name for invalid ascii characters to learn more about which ascii characters are allowed, review the section restrictions on ascii characters allowed to be used the configurator also validates the length of the string invalid ascii characters if an invalid character is found, a prompt is shown to the user invalid characters are marked in red as spaces are not a visible character, they can't be marked in red, so the user can make use of the comment added to the cell as well invalid string length to allow for the most efficient storage of the configuration as well as practicality when using an item name in a query, the maximum length of an item name can not exceed 50 characters if an item name is longer 50 characters, the user will be prompted note names of items which exceed the 50 character limit, will by default be trimmed to 50 characters if no action is taken by the user recommended item names to add it is recommended to add for each hierarchy level, including hierarchy level 0 directly under the node name, two items to store the start end end time of the event this allows litmus production record database to also calculate the duration of an event litmus does recommended to use the values start time for the start event and end time for the end event, as these are the default values used by the functions prorec prorec getprorecdatautc prorec prorec getprorecdatalocaltime and would not have to be changed when using the functions more about the use of these two functions can be reviewed in the chapters reading production record event data with local timestamp docid\ pfw2g0s705ff3qcouhpys and reading production record event data with utc timestamp docid\ zmrhs1q1rgiydzat6wf2z tip while a very common way of filling in spreadsheet style lists is to do it row by row, it has been observed that it can be beneficial to fill in all items first, especially if items are repeated throughout the data model hierarchy this can be achieved through the use of copy & paste cell content as well as make use of the ms excel autocomplete feature, where it does try to recognize what the user may want to enter as a repeat making use of these fast forms of duplication, can make it very quick to fill in all the names for the items filling in the example below was done in less than 1 minute adding an item description (optional) users are able to provide a description for an item to provide some context for colleagues about the purpose of the item and what it is used for the configurator will verify the item description for invalid ascii characters to learn more about which ascii characters are allowed, review the section restrictions on ascii characters allowed to be used the configurator also validates the length of the string invalid ascii characters if an invalid character is found, a prompt is shown to the user invalid characters are marked in red invalid string length to allow for the most efficient storage the maximum length of an item description can not exceed 256 characters if an item description is longer 256 characters, the user will be prompted note descriptions for items which exceed the 256 character limit, will by default be trimmed to 256 characters if no action is taken by the user defining the hierarchy position of an item to assign an item to its respective data model hierarchy level, users select a string representing the hierarchy level from the drop down menu in the column labeled node/level this will add the selected string into the cell note only values available through the drop down menu can be selected how to understand the strings shown by the drop down menu the column with the labeled node/level will provide the user with a drop down menu which shows the data model hierarchy levels as a string representation the first entry will always be a blank value this represents the hierarchy level 0 and is used for items placed directly under the node name this value will always be available, as each data model has by default a hierarchy level 0 if users have added additional hierarchy levels, the drop down menu will show them and their relations as a pipe symbol " | " separated string on how to add additional hierarchy levels, please review the chapters 2 defining the data model name and number of hierarchy levels docid\ rxq28wvkkcydozezewunw and 3 defining the hierarchy levels docid\ o1uexojspgm2ckaxstrru the string has to be read from the left, with the first value always being the name of a hierarchy level 1 any subsequent pipe symbol " | " separated value correlates to its respective hierarchy level 2nd value = hierarchy level 2 example station a| right side 3rd value = hierarchy level 3 example station a|right side| operation 1 4th value = hierarchy level 4 example station a|right side|operation 1| step 1 5th value = hierarchy level 5 example station a|right side|operation 1|step 1| function 1 tip if the user first entered all the items in the column labeled item name in the right order of their hierarchy level, the process of filling in the column labeled node/level can be speed up making use of the different options ms excel has for duplication of values across rows for example a users selects for the first item in a hierarchy level the string through the drop down menu then they simply duplicate this value to all the other items in the same hierarchy level in the picture below, the user has copied the value of row 7 shown by the interrupted green cell border and then selected rows 8 10 the user then simply pasted the value into the selected rows a second option is to make use of the ms excel autocomplete feature, where it does try to recognize what the user may want to enter as a repeat adding and engineering unit (optional) user can select an engineering unit for an item this can be used to provide some additional context when using the data recorded for a data model the solution provides a drop down with the most common engineering units used in the manufacturing industry adding an engineering unit can be beneficial for organizations which operate across different locations like north america and europa where the engineering unit provides the right context to the user and can help for example converting data between different unit systems to make sure, that users always compare "apples with apples" typically an engineering unit is most commonly used for numeric values setting the value type in accordance with the eav database model, values are stored in dedicated tables which store values of a specific data type litmus production record database supports four different data types value type string what data are stored example isnumber numeric values both integer decimal / float / real 25 124 14 isstring alphanumerical values sap2023051001 istime date and time value 2023 05 10 13 58 24 122 isboolean boolean values true 0 the user sets the value type by selecting it from the drop down menu in the column labeled value type this will add the selected string into the cell tip users can speed up the process by duplication the value type set for one item to other items with the same value type making use of the different option ms excel offers in this example, the user duplicated the istime value type, by first copying it shown by the interrupted green cell border and then selecting other items which are a time making use of ctrl+left click the user then pasted the value type into the selected rows a second option is to make use of the ms excel autocomplete feature, where it does try to recognize what the user may want to enter as a repeat defining identifiers litmus production record database makes use of identifiers to allow users to retrieve event data without having to know any internal database id or index the concept of identifiers for production events is explained in the chapter how are data recorded in litmus production record database docid\ ulfmhqnmwb91rkntbaqqn by default, every item will be set to the value no , as only up to a maximum of 5 identifiers can be defined the user selects which hierarchy level 0 items are an identifier by selecting the value yes from the drop down menu all identifiers have to be defined for hierarchy level 0, which means that the column labeled node/level is empty while identifiers have to be defined for hierarchy level 0, the configurator will initially not prevent the user from selecting the value yes for an item which is not defined for hierarchy level 0 to allow users the freedom of being able to change their minds and rearrange the configuration the configurator will not publish the data model if a none hierarchy level 0 item is set as identifier and report the fact