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IFC comparison table

When you have imported an IFC file into your requirements model, it is likely that you will want to compare the design specifications in the IFC file with the requirements in BriefBuilder.

For example: does the design model contain all the spaces that have been asked for? Are the room sizes right? The ceiling heights? The security zoning?

You can check such matters by using the IFC comparison table. This table can be found in the main menu, under the header IFC.

You can find the IFC comparison table in the main menu, under the header IFC

In this article we’ll explain the practicalities of this table.

Please note: for now, the IFC comparison table’s focus is on spaces and their properties. Technical systems and elements are not (yet) part of this functionality.

Also note: you can only make a meaningful comparison if the IFC spaces and the BriefBuilder spaces have been mapped properly (e.g. by means of a room number, a room name or the BriefBuilder ID). More explanation about this can be found here.

Selections

When clicking on IFC comparison in the menu, the first thing you get to see is a selection page.

Here, you can select a predefined comparison table (a table that has been made earlier by you or by another project participant) or you can create a new comparison table.

You can either select an existing comparison table or create a new one.

In this article, we’ll focus on how to create a new comparison table.

If you want to know more about how you can save table definitions for repeated usage, read this article.

Creating a table definition

To create a table definition, you must click on the button New.

You then get to see three selection blocks:

  • Requirements (to select BriefBuilder data)
  • Compare with (to select IFC data)
  • Acceptance criteria (to define the criteria that you want to apply to the comparison results)

Requirements

In this block, you can select the spaces and requirements that you want to use as the basis for your comparison.

First you have to select the spaces that you want to include in your comparison. The tree selection is by default set on the spaces & locations tree, which can be further narrowed down by selecting

  • a particular part of that tree
  • a particular label
  • a particular typical.

Next, you have to choose the requirement type you want to compare. You can choose between

  • a standard property (e.g. usable floor area or floor-to-ceiling height)
  • a related object (e.g. power socket or gas outlet).

When selecting related object you must select the specific object that should be part of your comparison. For this, you have to select:

  • the relevant tree (e.g. systems & elements or user equipment)
  • the object that you want to compare (e.g. a particular type of outlet)
When selecting ‘Related object’ as a requirement, do not forget to select the relevant object via the ‘Select object’ button.

Moreover, you must choose what kind of attribute of the related object you would like to compare:

  • Quantity (relevant when you want to compare countable matters, such as the number of power sockets)
  • Name (relevant when you want to compare ‘non-countable’ matters, such as the floor finishes).
In the case of a related object, do you simply want to compare its presence (> select name), or do you want to compare a quantity (> select quantity).

Compare with

In this block, you can select the IFC data that you want to use for your comparison.

Selection options:

  • Tree: the relevant tree, which is (for now) by default the IFC spaces tree.
  • Specification type: the type of data that you want to compare – by default set to IFC property.
  • IFC property: the specific IFC property that you want to use for your comparison.

Good to know: when selecting quantitative data, you can add a conversion factor. This is relevant when a BriefBuilder requirement has a different unit of measure than the corresponding IFC property.

For example: when a BriefBuilder requirement is expressed in meters, and the IFC property in millimeters, you must add 0,001 as the conversion factor to make the data comparable. See image below.

When unit of measure for the BriefBuilder requirement is different from the one of the IFC property, you have to add a conversion factor.

Good to know: when selecting the standard property quantity as requirement, the ‘compare with’ selection block will look slightly different as it will automatically select quantity for IFC as well. See below.

To compare space quantities, select ‘Quantity’ as standard property in the requirements block.

Acceptance criteria

In this block you can define the acceptance criteria concerning the comparison outcomes. These are:

  • Method: should there be an exact match between the IFC value and the requirement value, or are deviations allowed?

The option ‘deviations allowed‘ is only available if both the selected requirement and IFC property are quantitative. So, the input type for a property value should either be integer or decimal.

  • Max. lower deviation (in case of ‘deviations allowed’): to what extent is an IFC value allowed to be lower than the requirement value?
  • Max. upper deviation (in case of ‘deviations allowed’): to what extent is an IFC value allowed to be higher than the requirement value?

Both lower and upper deviations can be expressed as either percentages or absolute numbers.

Requirements vs. acceptance criteria

Acceptance criteria and requirements are closely related, but not necessary the same. The difference can best be explained by an example.

Let’s say that there is a requirement that states that the size of a meeting room should be at least 20 sqms (usable floor area ≥ 20 sqm).

This is a clear enough requirement. Yet, in reality, the client will probably also accept a meeting room that is a tiny bit smaller (e.g. 19,8 sqm). Likewise, the client will probably not accept a meeting room that is much bigger than what was asked for (e.g. 40 sqm).

This is where the acceptance criteria come into play. With these, you can define the range of acceptable solutions for your comparison.

In this case, you may e.g. specify a maximum lower deviation of 1 sqm (absolute number) and a maximum upper deviation of 10% (a percentage), which means that the aforementioned meeting room should have a size between 19 and 22 sqm.

This is obviously just an example. Acceptance criteria can differ per requirement type and even per project phase (more loose in the early phases, more strict towards completion).

When allowing deviations, you must specify how large these deviations are allowed to be, both downwards and upwards.

As mentioned earlier in this article: when you have defined the acceptance criteria and data that you want to compare, it is possible to save your selections. Read this article for more info.

Do you expect to make the comparison more than once? Save it and/or make it available to the rest of the team.

The comparison table

When ready with your selections, you can click on Show to see the comparison table.
Below, we’ll explain how to read and use this table.

Table set up

The table is divided into three sets of columns (which correspond with earlier mentioned selection blocks):

(1) Requirements: in this part of the table you will find spaces and requirements (the BriefBuilder data) against which you are comparing the IFC data.

Note that the header for the requirement column will change when choosing to compare another requirement.

Important to know: when comparing space quantities, the quantity on the BriefBuilder side of the table will show the total, calculated number of spaces of that type.

Example:

If you have a space called Bedroom (with a quantity of 3), and that space is part of a group of spaces called Appartement type A (with a quantity of 20), the comparison table will show a quantity of 60 (= 20 apartments x 3 bedrooms per apartment).

(2) Compare with: in this part of the table are the IFC spaces and attributes that you have selected to compare against the requirements.

(3) Comparison: this last part of the table shows the difference between the requirement value in BriefBuilder and the IFC value in the design model.

The last column shows the difference between the BriefBuilder value and the IFC value. If that difference is within the defined range of acceptable deviations, the cell turns green. If not, it turns red. If the values cannot be compared, the cell becomes yellow.

Please note: the comparison table does not show spaces for which there is nothing to compare. The following BriefBuilder spaces are not shown:

– Spaces that do not have a corresponding IFC space (according to the chosen mapping rule)
– Spaces that do not feature the selected property (no value, no note, no supporting file)
– Spaces that do not feature a relation to the selected object.

Legenda for deviations

The color coding of the deviation column indicates whether the deviation lies within the acceptable value range and, and thereby whether a design specification can be seen as compliant or non-compliant given the formulated acceptance criteria.

  • Green stands for compliant
  • Red stands for non-compliant
  • Yellow indicates that the comparison is not possible.

Concerning the last category: there can be various reasons for why it isn’t possible to get a comparison outcome. One obvious reason is a lack of data on either the requirements side or the IFC side.

Another possibility is that an IFC space is linked to multiple spaces in BriefBuilder. This happens when several BriefBuilder spaces have been combined into one design solution. In that case, the IFC space has to comply with multiple, potentially conflicting requirements, which means that an automatic comparison is not possible.

If a comparison isn’t possible, the underlying reason is shown in the hoover text in the yellow cell.

Comparison results for multiple IFC spaces

The IFC model often features more spaces than the BriefBuilder model does. This is because the BriefBuilder usually asks for space types, while the IFC model is an ‘instance’ model in which each space is an individual object.

For example: the BriefBuilder model may ask for a large meeting room with a quantity of 3. In BriefBuilder, this is one space object. In the IFC model, however, there will will be 3 individual meeting rooms (if designed according to the requirements), each with their own properties.

In the comparison table, these IFC spaces are shown individual rows. See image below.

One BriefBuilder space may correspond with multiple IFC spaces.

For determining the comparison outcome in such a case, the rule is that if one or more of the IFC spaces does not comply with the defined requirement, the overall comparison result will be ‘non compliant’.

See the example below in which one of the three IFC spaces do not meet the set acceptance criteria, and therefore the overall result for the comparison for this space is ‘non-compliant’.

In this example, one of the three IFC spaces does not meet the size requirement as defined in BriefBuilder, and therefore the overall result for the comparison for this requirement is ‘non-compliant’.

Comparison summaries

In the comparison column, you can also see result summaries on the levels of spaces groups and the overall building.

These summaries indicate how many of the requirements that are part of that group or building have been met. It shows the percentages of the requirements that the IFC model is compliant with.

In this example, two requirements have been met and one hasn’t. This shown in the summary as 66,7% of the requirements for which the result is ‘compliant’, and 33,3% for which it is ‘non-compliant’.

Expand/collapse rows

When there are many IFC spaces, you may prefer to collapse those rows and look at the ‘aggregated’ results only. This can be done by clicking on the icon in the table header ‘spaces’.

Collapse and expand all IFC rows by clicking on the icon in the column header.

The same can be done on the level of an individual BriefBuilder space by clicking the icon there.

Collapse and expand the IFC rows per space by clicking on the icon in front of the BriefBuilder space’s name..

Export to Excel

It is possible to export the comparison table to Excel via the export button that can be found next to the table’s name. The Excel export will go to your downloads folder.

Click on the Excel icon to make an Excel export.

Adjusting column sizes

Just like with the other overviews in BriefBuilder, you can adjust column widths by grabbing and moving the column header’s border.

Adjust a column’s width by grabbing the column header’s border.

Verification

If you are using BriefBuilder’s verification module, you may want to use the outcomes of your comparison as verification results.

This isn’t yet possible, but we are working on it. It will soon be available!

In the meantime, we recommend to work with two screens: one for the comparison table and one for the verification table. When you have filtered on the same BriefBuilder data (spaces, requirement type) in both tables, it is fairly easy to enter verification results manually.

But, as said, you’ll soon be able to ‘push’ the comparison results to the verification table!

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