Clear explanation of the differences between SXF and SFC — 6 checkpoints before transferring drawings

Table of Contents

• First clarify the difference between SXF and SFC

• Why SXF and SFC are easily confused in practice

• How SXF and SFC should be used differently in practice

• Checkpoint 1 Fix in words the format the recipient expects

• Checkpoint 2 Distinguish between final delivery and interim sharing

• Checkpoint 3 Confirm how much of the drawing will be reused

• Checkpoint 4 Separate display checks from edit checks

• Checkpoint 5 Do not overlook differences before and after conversion

• Checkpoint 6 Align understanding among all stakeholders

• Summary

First clarify the difference between SXF and SFC

Voices saying “I don’t really understand the difference between SXF and SFC” are very common in drawing exchange work. To conclude up front: SXF and SFC are not terms to be compared on the same footing. SXF is a common rule for exchanging drawing data between different CAD software. SFC, on the other hand, is one of the file formats defined within that SXF. In other words, SXF is the broader concept referring to the entire exchange standard, and SFC is a specific storage format contained within it. If you don’t sort this out at the outset, when the other party says “please provide it in SXF,” the conversation can proceed without confirming whether they mean P21 or SFC, making mismatches likely in later stages. CALS ocf.or.jp SXF mainly includes the P21 format and the SFC format: P21 is organized as a format that conforms to international standards, while SFC is organized as a simple domestic format. In practice, this difference becomes the starting point for how they are used. For example, in situations that require strictness for formal delivery or external handover, P21 tends to be the default, whereas for interim sharing among stakeholders where lightness and responsiveness are valued, SFC becomes a candidate. In other words, the correct order of thinking is not “SXF or SFC?” but “Which format within SXF should we use?” Just switching to this way of thinking makes the decision at drawing handover much simpler. ocf.or.jp What’s important here is not to be misled by similar-sounding terms. On site, people may say “SXF data” while actually referring to SFC, or conversely, when told “I’ll send it as SFC,” the receiver might assume “if it’s SXF-family drawings, it’s all the same.” However, because file specifications differ in reality, transferring files without sharing assumptions is risky. Even if the drawing appears to open, when someone later tries to edit or reuse it, they may find it behaves differently than expected. Correctly understanding the terminology is not just an academic matter but a practical step to prevent rework. ocf.or.jp

Why SXF and SFC are easily confused in practice

The biggest reason confusion arises is that conversations about transfers tend to be shortened. On site, exchanges like “Please output the drawing in SXF” or “Can you hand it over in SFC?” are routine, but the underlying specifications and operational conditions are not verbalized each time. Ideally, you should confirm what format it will be saved in, what the purpose is, whether the recipient only needs to view it or also edit it, and so on. In practice, deadlines are often prioritized, and the atmosphere leans toward “as long as it opens for now.” As a result, SXF as the broader framework and SFC as the concrete format are handled ambiguously. CALS ocf.or.jp What makes it more complicated is that SXF includes not only SFC but also P21. That means the word SXF alone does not sufficiently determine the actual handover conditions. The work required differs depending on whether the recipient wants “a drawing conforming to SXF,” “P21 intended for electronic delivery,” or “SFC for interim checks.” If this remains ambiguous, the sender may think they have responded properly, while the receiver feels “this is the wrong format.” The cause of confusion is not just lack of knowledge but the omission of details in conversation and insufficient confirmation of purpose. That is why it is important not only to know the differences but also to understand in which situations those differences become apparent. ocf.or.jp Another commonly overlooked point is that drawing handover cannot be evaluated solely by “whether it can be opened.” Certainly, if the receiver can display it, it may seem fine at first glance. But what causes real trouble for practitioners is the subsequent processes: handling layers, re-editing lines and text, overlaying with other drawings, future corrections, and integration into delivery data—the drawing is used after being opened. If expectations and reality diverge here, the initial handover may have been technically completed but is a failure as a business process. The reason the difference between SXF and SFC matters is precisely because it relates to how the drawing will be used after transfer. ocf.or.jp

How SXF and SFC should be used differently in practice

The practical approach is not complicated. First, separate whether the transfer is a formal deliverable or a mid-work share. Official documents indicate that CAD data file formats are in principle SXF (P21), and that P21 is used for electronic delivery. At the same time, they explain that for interim-stage data exchanges, SFC can be convenient for reasons of file size and processing speed. In short, if you prioritize strictness and standardization, choose P21; if you prioritize lightness and manageability, choose SFC. cals-ed.go.jp Translated into on-site language: decide based on whether it is the final deliverable to the client, for in-house confirmation, or for interim coordination with subcontractors. For final deliverables, matching the recipient’s operational rules and delivery requirements is the top priority. Therefore, if the recipient’s instructions assume P21, you should not choose SFC just for lightness. Conversely, if the drawing is not yet finalized and will be revised frequently in short intervals, there is benefit to choosing a lightweight, easy-to-handle format. The important thing is to select the format based on the stage of the process, not “somehow.” ocf.or.jp Also, although P21 and SFC can be mutually converted and no major practical problems are reported, since file specifications differ, strict differences can arise. Official explanations even cite differences in how angles are stored as examples. What this shows is that “because it can be converted, it’s safe” is not correct; rather, “it can be converted, but post-conversion checks are necessary.” If you want a reliable handover, do not stop at selecting the format—treat opening and checking under conditions close to the recipient’s environment as part of the work. ocf.or.jp

Checkpoint 1 Fix in words the format the recipient expects

The first checkpoint before handing over drawings is to fix in words the format the recipient really wants. The request “Please give it in SXF” is not enough information. You cannot tell whether that word means P21, whether SFC is acceptable, or whether either format under the SXF family will do. Proceeding with work while this remains ambiguous leads to after-the-fact recognition differences such as “We actually needed P21 this time” or “SFC would have been sufficient for checking.” The rework that can be prevented by a single confirmation is larger than you might imagine. CALS ocf.or.jp In practice, confirming not only the format name but also the intended use reduces mismatches. For example, asking “Is this for final submission?” “Is this for viewing/confirmation?” or “Will the recipient re-edit this?” raises the specificity of the required format immediately. Do not limit the format conversation to file extensions. The recipient does not need the file itself as an end—what they need is not to stop their subsequent work. If you can fix the purpose in the initial exchange, uncertainty in format selection is greatly reduced. Omitting this leaves all downstream processes uncertain. Format confirmation is a small task but the starting point for protecting drawing quality. ocf.or.jp

Checkpoint 2 Distinguish between final delivery and interim sharing

The second checkpoint is to be clear whether the transfer is a delivery or an interim share. This directly affects format selection. Official documents state that P21 should be used for electronic delivery, and that SFC may be convenient for interim-stage data exchange. In other words, even for the same drawing data, the appropriate format changes depending on the process position. If you do not separate these, you may choose a simple format when a strict format is needed for delivery, or inefficiently use a heavy format for internal sharing and reduce productivity. cals-ed.go.jp Practitioners often stumble when they judge “it’s still an interim stage, so a light format should be fine,” and that data then ends up being reused as the source for the final deliverable. In sites where the boundary between interim sharing and final delivery is blurred, this mismatch happens frequently. That is why you need to think one level deeper about the role of the data you are sending. Whether it is today’s shared material or the baseline data to be carried into the final deliverable changes the format to choose. Judge not by the process name but by what the data will be used for next—this is the shortcut to reducing transfer incidents. Distinguishing whether it is delivery or interim sharing also helps clarify responsibility. For final delivery, format selection is not just a matter of convenience but part of the product quality. Even for interim sharing, if the recipient will use the data directly for drawing review or quantity study, you cannot ignore display fidelity and stable loading. Treating format differences as process differences makes it easier to decide where to prioritize strictness and where to prioritize speed. When unsure about drawing handover, first re-question “What is this transfer for?” ocf.or.jp

Checkpoint 3 Confirm how much of the drawing will be reused

The third checkpoint is to confirm how extensively the recipient plans to reuse the drawing. Whether they will merely view it on-screen, use it as a base for corrections, repurpose it into another drawing, or incorporate it into a delivery file changes which format is appropriate. SXF is a common rule intended for exchanging 2D CAD data, and while P21 and SFC are both within the SXF family, their file specifications differ. Therefore, the deeper the recipient’s intended use, the more “opening” the file is not enough—what matters is “can it be handled as expected?” ocf.or.jp A common failure here is the sender providing data assuming viewing only, while the receiver accepts it assuming editing. This mismatch is not apparent immediately after transfer. Later, when corrections or integrations occur, people realize “the operation differs from what we expected,” prompting re-conversion or re-send requests. What you really want to avoid in drawing handover is not an immediate visible defect but a subtle rework discovered days later. That is why asking how much the recipient will touch the drawing in advance is important. ocf.or.jp When confirming the reuse scope, it helps to be aware of the recipient’s role. If the client or verifier will perform only visual checks, display convenience is the priority. If the person will use the drawing for design revisions or construction planning, ease of handling in subsequent processes is important. Knowing how far the drawing will be reused allows format selection to be part of business design rather than mere habit. Before handing over a drawing, verbalizing “what will the recipient do with this drawing?” significantly improves the accuracy of format selection. ocf.or.jp

Checkpoint 4 Separate display checks from edit checks

The fourth checkpoint is to separate display checks from edit checks. In drawing handover, people tend to feel relieved once the recipient can open and view the file. However, being able to display it is not the same as being able to use it in business processes. Official viewing tools are intended for display, printing, and assisting standard checks, and generally do not offer editing functions. This fact indicates that drawing data confirmation involves at least two stages: “does it look correct?” and “can the required tasks be performed?” cals-ed.go.jp For example, if the recipient will only open the drawing to check content, display fidelity checks will be the main focus. If there will be subsequent corrections or reuse, then editability and behavior after conversion must also be part of the checks. If you do not separate these, the false judgment “it opened, so there’s no problem” occurs. When checking before handing over, the sender should imagine the recipient’s working environment and decide what level of confirmation is necessary. Distinguishing between cases where display checks are sufficient and those where edit checks are required prevents unnecessary re-sends and returns. cals-ed.go.jp In practice, organizing these two types of checks separately greatly improves confirmation efficiency. First open and check the appearance. Then, only when necessary, check editing and reuse behavior. This order clarifies the purpose of checks. Conversely, attempting to check everything at once with an ambiguous purpose leads to omissions of important items or wasted time on unnecessary tasks. The pre-transfer check exists not to increase workload but to perform necessary checks at the correct granularity. The idea of separating display checks and edit checks is the basic approach for that purpose. cals-ed.go.jp

Checkpoint 5 Do not overlook differences before and after conversion

The fifth checkpoint is to not overlook differences before and after conversion. Although P21 and SFC are considered mutually convertible, because their file specifications differ, differences can strictly occur. Official explanations cite differences in how angles are preserved as an example; while no major practical problems have been reported, the possibility of differences is not denied. From this we learn that “can be converted” and “no confirmation needed” are distinct. When handover involves format conversion, trust the conversion process but always perform a final check with human eyes. ocf.or.jp Be especially cautious that people who know the original drawing well are less likely to notice post-conversion discomfort. Because they have the correct drawing image in their heads, they may overlook small discrepancies. That is why, in pre-transfer checks, it is important to temporarily remove assumptions tied to the original drawing and reopen it from the recipient’s perspective. Carefully check positional relationships of shapes, text legibility, sense of scale, and whether intended expressions have been preserved. Even if differences from format changes appear small, if they accumulate in subsequent processes, correction costs can rapidly increase. ocf.or.jp Difference checks are not only for “finding problems” but also to confirm “this format can be operated without issue.” If you can confirm conversion results are problem-free, you can choose formats with confidence in the future. If you skip confirmation, you will keep sending drawings with anxiety each time. To stabilize drawing handover quality, it is more important to build a mechanism for how to confirm after conversion than to trust conversion itself. Understanding formats and confirmation procedures together is what makes the knowledge usable in practice. ocf.or.jp

Checkpoint 6 Align understanding among all stakeholders

The sixth checkpoint is to align understanding among all stakeholders. Handover troubles arise more often from misaligned assumptions among people than from the file itself. The creator may think SFC is sufficient while the reviewer expects P21. Internally it may be intended only for viewing, but externally the recipient may treat it as a candidate for final delivery. Such mismatches are not the fault of individual staff but stem from insufficient sharing of format and usage. Therefore, before handing over a drawing, the team needs to align on who it is for, for what purpose, in which format, and in what state it will be handed over. CALS This alignment does not require an elaborate system. Simply standardizing file naming at handover, cover messages, storage location rules, and format selection criteria concisely can be effective. For example, clearly stating whether it is for final submission or interim checking when sending, or always indicating P21 or SFC, are small habits that greatly reduce downstream misunderstandings. Even if people know the format differences, it does not help in practice unless they are shared among stakeholders. Making the knowledge a standard handover procedure rather than leaving it in individual heads is the real prevention of recurrence. ocf.or.jp Moreover, once all stakeholders share the same understanding, format selection stops being person-dependent. Instead of relying on each person’s experience or intuition, the format can be chosen naturally according to the purpose. This is especially beneficial in busy sites. Reducing decision uncertainty shortens and sharpens pre-send checks. The purpose of understanding the difference between SXF and SFC is not simply to be able to explain it—it is to stabilize handover quality regardless of who is responsible. The final step toward that is building common understanding among all stakeholders. ocf.or.jp

Summary

To summarize the difference between SXF and SFC in one sentence: SXF is the common rule for exchanging drawings, and SFC is one of the file formats within it. Correctly understanding this relationship lets you decide not “SXF or SFC?” but “which SXF format to use according to the purpose.” Before handing over drawings, it is important to fix in words the format the recipient wants, distinguish between final delivery and interim sharing, confirm the reuse scope, separate display checks from edit checks, confirm differences before and after conversion, and align understanding among all stakeholders. Just following these six checkpoints can greatly reduce rework in drawing transfers. CALS cals-ed.go.jp When transferring drawing data, properly handling format differences is itself quality control. This idea applies equally to location information and measurement data handled on site. If you want to consistently organize not only drawings but also coordinate-equipped field data, using an iPhone-mounted high-precision GNSS positioning device like LRTK and streamlining the flow from acquisition to sharing can be effective. Reviewing how you handle on-site data together with organizing drawing formats makes it easier to further improve transfer accuracy and the reproducibility of overall work.