Chapter 3: OHLC Data Structure and Gap Analysis (Mechanics and Dynamics of Charting)

1. Overview

A chart is not merely a tool for visualizing price. The process of quantizing a continuous stream of market prices into four discrete data points — Open, High, Low, and Close (OHLC) — is itself an act of information filtering. Understanding which data points carry greater significance within this filtering process is the starting point of technical analysis.

This chapter clearly defines the significance hierarchy of OHLC data and classifies the four structural types of price gaps, analyzing the market implications of each. This content serves as the foundational infrastructure for all subsequent analysis, including candlestick interpretation, support/resistance identification, and volatility measurement.

Why does this matter? Many traders focus exclusively on the Close or treat all gaps as equivalent. However, once you understand the generative principles behind each OHLC component, you can distinguish which price levels are "created by the market" and which are "created by time settings."

2. Core Rules and Principles

2.1 The Nature of OHLC Data: Quantization of Continuous Price

The actual prices occurring in a market are continuous tick data. OHLC is the compression of this continuous data into four values by slicing it into specific time intervals.

Component	Generation Principle	Determining Agent
High	The highest point reached by buying pressure within the interval	Market participants
Low	The lowest point reached by selling pressure within the interval	Market participants
Open	The first traded price at the moment the time interval begins	Time setting
Close	The last traded price at the moment the time interval ends	Time setting

The reason this distinction matters is clear. The High and Low are outcomes produced by the market itself, while the Open and Close are mechanical artifacts that change depending on the timeframe set by the chart creator. Even with identical price data, the Open and Close differ completely between a 5-minute chart and a 1-hour chart, yet the High and Low covering the same time range remain unchanged.

2.2 OHLC Data Significance Hierarchy

Significance Ranking:

1. High and Low — Highest Significance

   • Price rejection zones generated by actual supply and demand forces in the market
   • They mark the point where buying pressure could no longer push price higher (High) and the point where selling pressure could no longer push price lower (Low)
   • These are the actual test points of support and resistance, and their essential meaning is preserved even when switching timeframes
   • Key insight: The High and Low directly show "where the market was rejected"

2. Open and Close — Conditional Significance

   • By default, these are artificial demarcation points determined by time interval settings
   • However, under specific conditions their significance increases substantially

Conditions Under Which Open/Close Significance Increases:

Condition	Reason	Example
Long gaps between trading sessions	Information accumulated during non-trading hours is reflected in the Open	Stock market overnight news → next day's Open
Higher timeframes	More participants' decisions are reflected	Weekly/monthly Open and Close
Large gap size	Signal of strong sentiment shift	Large gap after earnings announcement
Strong psychological meaning of open/close	Institutional order concentration, position unwinding	New York session closing price

Cryptocurrency Market Characteristics: In the 24-hour cryptocurrency market, there are no inter-session gaps, so the significance of the daily Open/Close is relatively lower compared to traditional markets. Therefore, High/Low-centric analysis is even more important in cryptocurrency trading. However, in derivatives with defined trading hours, such as CME Bitcoin futures, gaps occur frequently, and in these cases the significance of the Open increases.

2.3 Four Gap Types Classification

Definition of a Gap: A price range between two consecutive trading sessions where no trading activity occurred. Gaps indicate that market sentiment shifted sharply during non-trading hours, and their technical meaning varies significantly by type.

---

Type 1 Gap — Basic Opening Gap

• Definition: The price difference between the Previous Close and the Next Open
• Calculation: Gap = Next Open - Previous Close
• Characteristics: The most common and frequently observed gap form
• Limitation: Since both the Close and Open are products of time settings, this difference arises from session demarcation rather than market forces
• Significance: Relatively low — does not provide a strong technical signal on its own

---

Type 2 Gap — High/Low to Open Gap

• Definition: The price difference between the Previous High or Low and the Next Open
• Bullish gap: Gap = Next Open - Previous High (when positive)
• Bearish gap: Gap = Previous Low - Next Open (when positive)
• Characteristics: More meaningful than Type 1 because it measures the divergence between the previous session's extremes and the next session's starting point. A combination of market-generated extremes (High/Low) and time-generated values (Open)
• Significance: Medium — serves as a criterion for determining whether price has completely exited the previous trading range

---

Type 3 Gap — True Window Gap

• Definition: A complete price separation between the Previous High/Low and the Next High/Low
• Bullish window: Previous High < Next Low → the price ranges of the two bars are completely separated
• Bearish window: Previous Low > Next High → the price ranges of the two bars are completely separated
• Characteristics: The most important gap among all four types. A pure void zone where the actual trading ranges (High to Low) of two sessions do not overlap at all
• Function: Acts as powerful support/resistance. This is what Japanese candlestick analysis calls a "Window" (窓, Mado)
• Meaning: Indicates a dramatic shift in market sentiment or strong trend continuation

Practical Point: Unlike other gap types, Type 3 gaps are composed entirely of market-generated values (High/Low). This is why they are the most reliable type of gap.

---

Type 4 Gap — Close to High/Low Gap

• Definition: The price difference between the Previous Close and the Next High or Low
• Characteristics: This is the gap type used when calculating True Range in the ATR (Average True Range) developed by Welles Wilder
• Relationship to the True Range Formula:
  • TR = max(Current High - Current Low, |Current High - Previous Close|, |Current Low - Previous Close|)
  • The difference between the Previous Close and the Current High/Low corresponds to the Type 4 gap
• Purpose: Ensures consistency in volatility measurement by incorporating inter-session price changes into range calculations

---

Gap Type Comparison Summary:

Type	Components	Market-Generated Ratio	Significance	Primary Use
Type 1	Close ↔ Open	0% (both time artifacts)	★☆☆☆☆	Basic gap recognition
Type 2	High/Low ↔ Open	50%	★★★☆☆	Range breakout assessment
Type 3	High/Low ↔ High/Low	100% (both market-generated)	★★★★★	Key support/resistance
Type 4	Close ↔ High/Low	50%	★★★☆☆	ATR/volatility measurement

2.4 Relationship to Traditional Gap Classification

Separately from the four structural gap types above, technical analysis also classifies gaps by their market context as follows. Understanding both classification systems together deepens the quality of gap analysis.

Contextual Classification	Location of Occurrence	Fill Probability	Relationship to Structural Types
Common Gap	Within consolidation ranges	High	Mostly Type 1, 2
Breakaway Gap	At pattern/range breakouts	Low	Mostly Type 2, 3
Runaway/Measuring Gap	Mid-trend	Very low	Mostly Type 3
Exhaustion Gap	End of a trend	High	Can be Type 2 or 3

3. Chart Verification Methods

3.1 OHLC Data Significance Verification

High/Low Verification Procedure:

1. Confirm price rejection reactions at High/Low points — observe whether long wicks have formed
2. Check for volume spikes at those levels — volume accompaniment increases the significance of that level
3. Observe repeated support/resistance tests at the same level — multiple approaches to the same High/Low level increase its importance
4. Verify whether breakouts are accompanied by volume — breakouts without volume have a high probability of being fakeouts

Open/Close Significance Verification Procedure:

1. Observe significance changes across timeframes

   • 1-minute to 15-minute: Open/Close significance is low (time divisions are arbitrary)
   • Daily: Open/Close significance is medium (a day represents a natural cycle)
   • Weekly/Monthly: Open/Close significance is high (reflects sufficient participant decision-making)

2. Verify whether the Open's role as support/resistance strengthens when gaps occur

3. Confirm that significance increases when inter-session gaps are longer — more information is compressed into the Open

4. For the Close, checking whether it aligns with the POC (Point of Control) on the Volume Profile enhances reliability

3.2 Gap Type Verification Methods

Type 3 Gap (Window Gap) Verification:

1. Confirm complete price window formation — the High-Low ranges of two adjacent bars must not overlap at all
2. Observe whether price bounces when approaching the window boundary — stronger bounces indicate higher gap validity
3. Check the correlation between window size and support/resistance strength — generally, larger windows form stronger barriers
4. Observe the timing and manner of gap fill — quick fills weaken significance; prolonged maintenance indicates a key level

Gap Size and Significance Verification:

1. Calculate gap size as a percentage of ATR — Gap Size / ATR(14) × 100
2. Gaps exceeding 50% of ATR are considered significant; those exceeding 100% are considered very strong
3. Check alignment between gap direction and existing trend — gaps aligned with the trend are continuation signals; gaps in the opposite direction may signal reversal

Type 4 Gap and ATR Relationship Verification:

1. Verify how Type 4 gaps are reflected in True Range within ATR calculations
2. Instruments with frequent Type 4 gaps will produce ATR values significantly larger than simple High-Low ranges
3. The greater this difference, the higher the inter-session volatility — this must be factored into position sizing

4. Common Mistakes and Cautions

4.1 OHLC Data Interpretation Mistakes

❌ Excessive Reliance on the Close

• Mistake: Determining support/resistance solely from the Close across all timeframes and drawing trendlines based only on closing prices
• Problem: The Close is a product of time settings and changes completely when the timeframe is altered
• Solution: Prioritize High/Low-based criteria when identifying support/resistance. Use Close-based analysis as a secondary confirmation tool
• Exception: Indicators that use the Close as an input value, such as moving average calculations, treat the Close as the standard — this is a separate context

❌ Overvaluing Open/Close on Lower Timeframes

• Mistake: Setting the Open and Close of a 5-minute bar as key levels
• Problem: A 5-minute interval is entirely arbitrary; dividing the same time into 3-minute or 7-minute bars produces completely different Open and Close values
• Solution: Focus on High/Low-centric analysis on lower timeframes and reference Open/Close only on daily charts and above

4.2 Gap Analysis Mistakes

❌ Failing to Classify Gap Types

• Mistake: Calling all gaps simply "gaps" and analyzing them the same way
• Problem: The technical meaning of a Type 1 gap and a Type 3 gap are entirely different
• Solution: When a gap occurs, always classify which of the four types it belongs to before proceeding with analysis
• Key point: Only Type 3 gaps (window gaps) serve as true support/resistance

❌ Blind Faith in "All Gaps Get Filled"

• Mistake: Automatically entering counter-trend positions whenever a gap occurs
• Problem: Breakaway gaps and runaway gaps may never be filled, or filling may take months to years
• Solution: Consider both the structural type (Type 1–4) and the contextual classification (common/breakaway/runaway/exhaustion) together
• Practical rule: Type 1 and 2 gaps have a high probability of being filled. Type 3 gaps classified as breakaway or runaway gaps tend to resist filling

❌ Considering Only the Absolute Size of a Gap

• Mistake: Judging that "a $500 gap is a large gap"
• Problem: A $500 gap in Bitcoin and a $500 gap in Ethereum carry entirely different meanings
• Solution: Always evaluate using relative size against ATR. Using the percentage relative to ATR(14) enables cross-asset comparison

❌ Overusing Gap Analysis in Cryptocurrency Spot Markets

• Mistake: Actively searching for gaps on 24-hour cryptocurrency spot charts
• Problem: Structural gaps rarely occur in continuously traded markets. When they do, they are mostly caused by insufficient liquidity
• Solution: Conduct cryptocurrency gap analysis on markets with defined sessions such as CME futures charts, and focus on High/Low-based analysis for spot charts

5. Practical Application Tips

5.1 OHLC Data Utilization Strategy

Tiered Application Principle by Timeframe:

Timeframe	Analysis Focus	Open/Close Utility	Notes
1-min to 15-min	High/Low centric	Low	Open/Close can be effectively ignored
1-hour to 4-hour	High/Low priority, Open/Close supplementary	Medium	Reference the Open at major session start times
Daily	Balanced consideration of all OHLC	High	The position of Open/Close is key to candlestick pattern interpretation
Weekly/Monthly	All OHLC highly important	Very high	Monthly Close is linked to institutional rebalancing

Criteria for Upgrading Open Significance When Gaps Occur:

• When gap size exceeds 50% of ATR(14) → mark the Open as potential support/resistance
• When gap direction aligns with the existing trend → the Open's support/resistance function is strengthened
• When inter-session intervals exceed 48 hours (e.g., weekends) → Open significance doubles

5.2 Gap Trading Strategies

Type 3 Gap (Window Gap) Strategy:

1. After gap formation, designate the entire window area as a support/resistance zone
2. Consider bounce trades when price approaches window boundaries — the upper edge acts as resistance, the lower edge as support
3. If the window is completely penetrated (filled), recognize it as a signal of trend weakening or reversal
4. Larger gaps carry stronger signals — window gaps exceeding 100% of ATR are medium-term key levels

Gap Fill Strategy by Type:

Gap Type	Fill Probability	Strategy Direction	Notes
Type 1	High	Consider counter-direction entry	Smaller gaps tend to fill faster
Type 2	Medium to high	Consider counter-direction entry after confirmation	Whether previous High/Low is breached is key
Type 3	Low	Prefer trend-direction entry	Use the gap zone as a stop-loss reference
Type 4	N/A	Use as a volatility indicator	Applied to risk management rather than direct trading

5.3 Combining with Other Indicators and Patterns

Combined Analysis with Volume:

• When volume spikes accompany the High/Low, the reliability of that level as support/resistance increases significantly
• When Type 3 gap formation coincides with volume exceeding 2× the average, the gap's persistence is high
• Gaps with minimal volume (especially during low-liquidity hours) have a high probability of rapid fill

Combination with Moving Averages:

• If price settles above a key moving average (20 EMA, 50 SMA, etc.) after a gap, the gap's validity is reinforced
• Zones where a Type 3 gap area overlaps with a moving average form powerful composite support/resistance

Combination with RSI/Stochastic:

• If RSI reaches overbought territory after a gap up, check for the possibility of an exhaustion gap
• When RSI divergence appears simultaneously with the gap direction, the probability of gap fill increases

Combination with Bollinger Bands:

• If a Type 3 gap forms outside the Bollinger Bands, it signals extreme volatility — contextual judgment is needed to determine whether it is an exhaustion gap or a breakaway gap

5.4 Risk Management Application

Gap-Based Stop-Loss Placement:

• Use the opposite boundary of a Type 3 gap as a stop-loss reference point — for a bullish window gap, place the stop below the lower edge of the window
• If the gap zone is completely filled, the premise of the existing position is invalidated, so consider immediate liquidation

Position Sizing:

• Since stop-loss width increases proportionally with gap size, adjust position size inversely
• Position Size = Allowable Loss / (Gap Size + Buffer)

Response When Gap Fill Fails:

• If price enters the gap zone and then exits back in the original gap direction → confirmation signal of the existing trend
• If price completely fills the gap and continues in the opposite direction → recognize it as a trend reversal signal and reassess positions