What Is Reserved Interface (虛一待用), the One-Gap Sequence, in BaZi?
Learn the Jia–Yi–Bing–Wu example, its missing Ding stem, the repeated-branch contrast and the limits of the terse 虛一待用 rule.
Overview
Reserved Interface is the workbook’s legacy English label for 虛一待用; “One Gap Reserved for Use” better describes the recorded rule. San Ming Tong Hui says the four original stems are connected but skip one character, using Jia, Yi, Bing and Wu with Ding missing. It then contrasts a branch sequence that repeats one character—Zi, Zi, Chou, Yin—and attaches an adverse traditional verdict. The passage does not define stem order, wraparound, pillar order, hidden stems, allowable gaps or a complete sequence table. OpenFate does not detect this formation, and it does not reproduce the source’s lifespan claim.
At a glance
- Recorded stem example
- Jia, Yi, Bing, Wu
- Reserved character
- Ding is the single missing stem
- Logic
- Four connected stems skip exactly one character
- Branch contrast
- Zi, Zi, Chou, Yin repeats one branch
- Safety boundary
- The adverse lifespan verdict is not reproduced
- Product boundary
- No OpenFate one-gap detector
The source gives one concrete near-consecutive stem sequence
Jia, Yi and Bing are followed by Wu, leaving Ding as the one missing character. The recorded logic is therefore not simply “four different stems” and not any collection that happens to omit one of the Ten Heavenly Stems.
The phrase “original stems of the four pillars are connected” may imply visible pillar stems, but the passage does not explicitly define order or whether rearranged pillars still count. The example should remain the evidence anchor.
- Show the four stems and identify the single internal gap.
- Do not treat any four distinct stems as the named sequence.
The repeated-branch example is a contrast, not a second formation rule
The text next gives Zi, Zi, Chou and Yin as a branch sequence that repeats one character and calls it “head-heavy and tail-light.” That example explains what the author disfavored; it does not establish a general branch-scoring system.
Its attached prediction of early death belongs to historical source language. OpenFate records that the claim exists but does not present it as evidence about health, mortality or a person’s future.
- Label Zi–Zi–Chou–Yin as the source’s contrasting example.
- Omit the historical lifespan verdict from user-facing prediction.
Sequence boundaries and reorderings remain unresolved
The passage does not say whether Gui can wrap to Jia, whether the missing character must be internal, whether the stems must appear year-to-hour, or whether hidden stems, combinations and transformations participate.
Without those rules, a detector would need to invent policy. OpenFate therefore does not label a chart Reserved Interface or use a near-consecutive stem count in reports.
- Do not assume wraparound, sorting or hidden-stem participation.
- Leave the result unresolved outside the recorded example.
A clean sequence does not guarantee advancement
The source praises the stem example with an image of steady advancement. That phrase is a traditional valuation, not evidence of education, promotion, status or a smooth life course.
Do not infer intelligence, career success, authority, income, wealth, personality, relationships, health, safety or lifespan from either the gap or repeated-branch example.
- No education, promotion, status or wealth guarantee.
- No personality, relationship, health, safety or lifespan prediction.
Sources and editorial basis
- 《三命通會》 (Sanming Tonghui)《三命通會》卷六「虛一待用」：四柱本干相連而跳一字，以甲乙丙戊缺丁為例；另以本支相連而重一字的子子丑寅作頭重尾輕反例，並附古代壽夭結果語A historical compilation covering stems and branches, Ten Gods, Nayin, Shen Sha, and multiple classical pattern systems.
- OpenFate Editorial Methodology甲乙丙戊與單一內缺丁按原例列證，子子丑寅僅作對比；原文未定年月日時順序、重新排序、癸甲循環、端點缺字、藏干及合化，不自行補表，產品未實作則不判、不採壽夭語、不改報告儲存，並排除學歷升遷地位收入財富性格關係健康安全壽命推斷OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.