Snowballing

Citation-based paper discovery through forward and backward snowballing.

Overview

Expand a systematic review by following citation chains from key papers.

Forward snowballing: Find papers that CITE a key paper (newer work building on it) Backward snowballing: Find papers CITED BY a key paper (foundational work it builds on)

Commands

Forward Citations (papers citing this one)

uvx scimesh workspace snowball {review_path}/ "10.1234/key-paper" --direction in -n 50

Backward Citations (references)

uvx scimesh workspace snowball {review_path}/ "10.1234/key-paper" --direction out -n 50

Both Directions

uvx scimesh workspace snowball {review_path}/ "10.1234/key-paper" --direction both -n 50

Command Options

uvx scimesh workspace snowball {review_path}/ "DOI" \
    --direction in|out|both \     # Citation direction
    -p openalex,semantic_scholar \ # Providers (default: both)
    -n 50 \                        # Max results per direction
    --scihub                       # Enable Sci-Hub for PDFs (optional)

Provider Support

Workflow

Step 1: Identify Seed Papers

After screening, identify 3-5 highly relevant papers to use as seeds:

{
    "question": "Which papers should we use as seeds for snowballing?",
    "header": "Seeds",
    "options": [
        {"label": "Top cited (Rec)", "description": "Use 5 most-cited included papers"},
        {"label": "Most relevant", "description": "Choose based on relevance to RQ"},
        {"label": "Seminal works", "description": "Known foundational papers"}
    ],
    "multiSelect": False
}

Step 2: Connectivity Check

BEFORE running snowballing, ask about connectivity and Sci-Hub:

{
    "questions": [
        {
            "question": "Are you connected to institutional VPN?",
            "header": "VPN",
            "options": [
                {"label": "Yes, VPN active", "description": "Better access + Scopus citations"},
                {"label": "No VPN", "description": "Will use Open Access only"},
                {"label": "Wait, connecting...", "description": "Pause for VPN connection"}
            ],
            "multiSelect": False
        },
        {
            "question": "Enable Sci-Hub for PDF downloads?",
            "header": "Sci-Hub",
            "options": [
                {"label": "No (Rec)", "description": "Only legal Open Access sources"},
                {"label": "Yes", "description": "Use --scihub flag (at your own risk)"}
            ],
            "multiSelect": False
        }
    ]
}

• If user chooses "Wait", pause and ask again when ready
• If user enables Sci-Hub, add --scihub flag to snowball commands

Step 3: Run Snowballing

For each seed paper:

# Forward: who cites this?
uvx scimesh workspace snowball {review_path}/ "DOI" --direction in -n 100

# Backward: who does this cite?
uvx scimesh workspace snowball {review_path}/ "DOI" --direction out -n 50

# Both at once
uvx scimesh workspace snowball {review_path}/ "DOI" --direction both -n 50

Step 4: Automatic Deduplication

The workspace snowball command automatically:

• Deduplicates against existing papers in papers.yaml
• Records in searches.yaml with type: snowball, seed_doi, direction
• Papers track which searches found them via search_ids
• Downloads PDFs when available (Open Access)
• Updates workspace stats

Step 5: Screen New Papers

Use scimesh:screening to screen the newly added papers.

Iterative Snowballing

For comprehensive reviews, repeat snowballing on newly included papers until saturation (no new relevant papers found).

digraph snowball {
    rankdir=LR;

    seeds [label="Seed papers\n(5 included)"];
    forward [label="Forward\ncitations"];
    backward [label="Backward\ncitations"];
    screen [label="Screen\nnew papers"];
    include [label="Newly\nincluded"];

    seeds -> forward;
    seeds -> backward;
    forward -> screen;
    backward -> screen;
    screen -> include;
    include -> forward [label="iterate"];
    include -> backward [label="iterate"];
}

Example Session

User: "Let's do snowballing on the included papers"

Agent: Lists included papers, identifies top 5 by citation count

Agent: For each seed:
       uvx scimesh workspace snowball ./review/ "DOI" --direction both -n 50

Agent: Reports: "Added 127 new papers (89 forward, 38 backward, 23 duplicates removed)"

Agent: [Uses scimesh:screening to screen new papers]

Integration with SLR Workflow

Snowballing typically happens AFTER initial screening:

1. scimesh:protocoling - Define protocol
2. scimesh:searching - Initial search
3. scimesh:screening - Screen initial results
4. scimesh:snowballing - Expand via citations (YOU ARE HERE)
5. scimesh:screening - Screen snowballed papers
6. scimesh:extracting - Extract evidence
7. scimesh:synthesizing - Generate PRISMA