'…we want the target dead or saved…we gotta get away from platform centric thinking…and we gotta focus on this thing where the sum of the wisdom is a cursor over the target…and we're indifferent [to the source]' — Gen. John Jumper

CoT Library

A comprehensive Go library for creating, validating, and working with Cursor-on-Target (CoT) events.

Features

• High-performance processing: Sub-microsecond event creation, millions of validations/sec
• Complete CoT event creation and manipulation
• XML serialization and deserialization with security protections
• Full CoT type catalog with metadata
• Zero-allocation type lookups and optimized memory usage
• How and relation value support with comprehensive validation
• Coordinate and spatial data handling
• Event relationship management
• Type validation and registration
• Secure logging with slog
• Thread-safe operations
• Detail extensions with round-trip preservation
• GeoChat message and receipt support
• Predicate-based event classification
• Security-first design
• Wildcard pattern support for types
• Type search by description or full name

Installation

go get github.com/NERVsystems/cotlib

Note: Schema validation relies on the libxml2 library and requires CGO to be enabled when building. See MIGRATION.md for guidance when upgrading from older versions.

Usage

Creating and Managing CoT Events

package main

import (
    "fmt"
    "log/slog"
    "os"
    "github.com/NERVsystems/cotlib"
)

func main() {
    logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

    // Create a new CoT event
    event, err := cotlib.NewEvent("UNIT-123", "a-f-G", 37.422, -122.084, 0.0)
    if err != nil {
        logger.Error("Failed to create event", "error", err)
        return
    }

    // Add detail information
    event.Detail = &cotlib.Detail{
        Contact: &cotlib.Contact{
            Callsign: "ALPHA-7",
        },
        Group: &cotlib.Group{
            Name: "Team Blue",
            Role: "Infantry",
        },
    }

    // Add relationship link
    event.AddLink(&cotlib.Link{
        Uid:      "HQ-1",
        Type:     "a-f-G-U-C",
        Relation: "p-p",
    })

    // Convert to XML
    xmlData, err := event.ToXML()
    if err != nil {
        logger.Error("Failed to convert to XML", "error", err)
        return
    }

    fmt.Println(string(xmlData))
}

Building Events with EventBuilder

builder := cotlib.NewEventBuilder("B1", "a-f-G", 34.0, -117.0, 0).
    WithContact(&cotlib.Contact{Callsign: "ALPHA"}).
    WithGroup(&cotlib.Group{Name: "Team Blue", Role: "Infantry"}).
    WithStaleTime(time.Now().Add(10 * time.Second))
event, err := builder.Build()
if err != nil {
    log.Fatal(err)
}
_ = event

Parsing CoT XML

package main

import (
    "errors"
    "fmt"
    "github.com/NERVsystems/cotlib"
)

func main() {
    xmlData := `<?xml version="1.0" encoding="UTF-8"?>
<event version="2.0" uid="UNIT-123" type="a-f-G" time="2023-05-15T18:30:22Z"
       start="2023-05-15T18:30:22Z" stale="2023-05-15T18:30:32Z">
  <point lat="37.422000" lon="-122.084000" hae="0.0" ce="9999999.0" le="9999999.0"/>
  <detail>
    <contact callsign="ALPHA-7"/>
    <group name="Team Blue" role="Infantry"/>
  </detail>
</event>`

    // Parse XML into CoT event
    event, err := cotlib.UnmarshalXMLEvent(context.Background(), []byte(xmlData))
    if err != nil {
        fmt.Printf("Error parsing XML: %v\n", err)
        return
    }

    // Access event data
    fmt.Printf("Event Type: %s\n", event.Type)
    fmt.Printf("Location: %.6f, %.6f\n", event.Point.Lat, event.Point.Lon)
    fmt.Printf("Callsign: %s\n", event.Detail.Contact.Callsign)

    // Check event predicates
    if event.Is("friend") {
        fmt.Println("This is a friendly unit")
    }

    if event.Is("ground") {
        fmt.Println("This is a ground-based entity")
    }
}

Handling Detail Extensions

CoT events often include TAK-specific extensions inside the <detail> element. cotlib preserves many of these extensions and validates them using embedded TAKCoT schemas. These extensions go beyond canonical CoT and include elements such as:

• __chat
• __chatReceipt
• __chatreceipt
• __geofence
• __serverdestination
• __video
• __group
• archive
• attachmentList
• environment
• fileshare
• precisionlocation
• takv
• track
• mission
• status
• shape
• strokecolor
• strokeweight
• fillcolor
• labelson
• uid
• bullseye
• routeInfo
• color
• hierarchy
• link
• usericon
• emergency
• height
• height_unit
• remarks

The remarks extension now follows the MITRE CoT Remarks Schema and includes a <remarks> root element, enabling validation through the tak-details-remarks schema.

All of these known TAK extensions are validated against embedded schemas when decoding and during event validation. Invalid XML will result in an error. Chat messages produced by TAK clients often include a <chatgrp> element inside <__chat>. cotlib first validates against the standard chat schema and automatically falls back to the TAK-specific tak-details-__chat schema so these messages are accepted.

Example: adding a shape extension with a strokeColor attribute:

event.Detail = &cotlib.Detail{
    Shape: &cotlib.Shape{Raw: []byte(`<shape strokeColor="#00FF00"/>`)},
}

Any unknown elements are stored in Detail.Unknown and serialized back verbatim. Unknown extensions are not validated. Although cotlib enforces XML size and depth limits, the data may still contain unexpected or malicious content. Treat these elements as untrusted and validate them separately if needed.

xmlData := `<?xml version="1.0"?>
<event version="2.0" uid="EXT-1" type="t-x-c" time="2023-05-15T18:30:22Z" start="2023-05-15T18:30:22Z" stale="2023-05-15T18:30:32Z">
  <point lat="0" lon="0" ce="9999999.0" le="9999999.0"/>
  <detail>
    <__chat chatroom="room" groupOwner="false" senderCallsign="Alpha">
      <chatgrp id="room" uid0="u0"/>
    </__chat>
    <__video url="http://example/video"/>
  </detail>
</event>`

evt, _ := cotlib.UnmarshalXMLEvent(context.Background(), []byte(xmlData))
out, _ := evt.ToXML()
fmt.Println(string(out)) // prints the same XML

The id attribute on __chat and __chatreceipt elements is optional.

Chat now exposes additional fields such as Chatroom, GroupOwner, SenderCallsign, Parent, MessageID and a slice of ChatGrp entries representing group membership.

GeoChat Messaging

cotlib provides full support for GeoChat messages and receipts. The Chat structure models the __chat extension including optional <chatgrp> elements and any embedded hierarchy. Incoming chat events automatically populate Event.Message from the <remarks> element. The Marti type holds destination callsigns and Remarks exposes the message text along with the source, to, and time attributes.

Chat receipts are represented by the ChatReceipt structure which handles both __chatReceipt and TAK-specific __chatreceipt forms. Parsing falls back to the TAK schemas when required so messages from ATAK and WinTAK are accepted without extra handling.

Example of constructing and serializing a chat message:

evt, _ := cotlib.NewEvent("GeoChat.UID.Room.example", "b-t-f", 0, 0, 0)
evt.Detail = &cotlib.Detail{
    Chat: &cotlib.Chat{
        ID:             "Room",
        Chatroom:       "Room",
        GroupOwner:     "false",
        SenderCallsign: "Alpha",
        ChatGrps: []cotlib.ChatGrp{
            {ID: "Room", UID0: "AlphaUID", UID1: "BravoUID"},
        },
    },
    Marti: &cotlib.Marti{Dest: []cotlib.MartiDest{{Callsign: "Bravo"}}},
    Remarks: &cotlib.Remarks{
        Source: "Example.Alpha",
        To:     "Room",
        Text:   "Hello team",
    },
}
out, _ := evt.ToXML()

Note: the groupOwner attribute is mandatory for TAK chat messages. It must be present for schema validation to succeed when using the TAK chat format.

Delivery or read receipts can be sent by populating Detail.ChatReceipt with the appropriate Ack, ID, and MessageID fields.

Validator Package

The optional validator subpackage provides schema checks for common detail extensions. validator.ValidateAgainstSchema validates XML against embedded XSD files. Event.Validate automatically checks extensions such as __chat, __chatReceipt, __group, __serverdestination, __video, attachment_list, usericon, and the drawing-related details using these schemas. All schemas in this repository's takcot/xsd directory are embedded and validated, including those like Route.xsd that reference other files.

Type Validation and Catalog

The library provides comprehensive type validation and catalog management:

package main

import (
    "errors"
    "fmt"
    "log"
    "github.com/NERVsystems/cotlib"
)

func main() {
    // Register a custom CoT type
    if err := cotlib.RegisterCoTType("a-f-G-U-C-F"); err != nil {
        log.Fatal(err)
    }

    // Validate a CoT type
    if err := cotlib.ValidateType("a-f-G-U-C-F"); err != nil {
        if errors.Is(err, cotlib.ErrInvalidType) {
            log.Fatal(err)
        }
    }

    // Look up type metadata
    fullName, err := cotlib.GetTypeFullName("a-f-G-E-X-N")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Full name: %s\n", fullName)
    // Output: Full name: Gnd/Equip/Nbc Equipment

    // Get type description
    desc, err := cotlib.GetTypeDescription("a-f-G-E-X-N")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Description: %s\n", desc)
    // Output: Description: NBC EQUIPMENT

    // Retrieve full type information
    info, err := cotlib.GetTypeInfo("a-f-G-E-X-N")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s - %s\n", info.FullName, info.Description)
    // Output: Gnd/Equip/Nbc Equipment - NBC EQUIPMENT

    // Batch lookup for multiple types
    infos, err := cotlib.GetTypeInfoBatch([]string{"a-f-G-E-X-N", "a-f-G-U-C"})
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Batch size: %d\n", len(infos))

    // Search for types by description
    types := cotlib.FindTypesByDescription("NBC")
    for _, t := range types {
        fmt.Printf("Found type: %s (%s)\n", t.Name, t.Description)
    }

    // Search for types by full name
    types = cotlib.FindTypesByFullName("Equipment")
    for _, t := range types {
        fmt.Printf("Found type: %s (%s)\n", t.Name, t.FullName)
    }
}

catalog.Upsert precomputes upper-case versions of each type's FullName and Description. FindByDescription and FindByFullName reuse these cached strings so searches are allocation-free.

Type Validation

The library enforces strict validation of CoT types:

• Basic syntax checking
• Standard prefix validation
• Length limits
• Wildcard pattern validation
• Type catalog verification
• Automatic resolution of f, h, n, or u segments to catalog entries containing .

// Examples of different validation scenarios:
cotlib.ValidateType("a-f-G")             // Valid - Friendly Ground
cotlib.ValidateType("b-m-r")             // Valid - Route
cotlib.ValidateType("invalid")           // Error - Unknown type

How and Relation Values

The library provides full support for CoT how values (indicating position source) and relation values (for event relationships):

How Values

How values indicate the source or method of position determination:

package main

import (
    "errors"
    "fmt"
    "log"
    "github.com/NERVsystems/cotlib"
)

func main() {
    // Create an event
    event, _ := cotlib.NewEvent("UNIT-123", "a-f-G", 37.422, -122.084, 0.0)
    
    // Set how value using descriptor (recommended)
    err := cotlib.SetEventHowFromDescriptor(event, "gps")
    if err != nil {
        log.Fatal(err)
    }
    // This sets event.How to "h-g-i-g-o"
    
    // Or set directly if you know the code
    event.How = "h-e" // manually entered
    
    // Validate how value
    if err := cotlib.ValidateHow(event.How); err != nil {
        if errors.Is(err, cotlib.ErrInvalidHow) {
            log.Fatal(err)
        }
    }
    
    // Get human-readable description
    desc, _ := cotlib.GetHowDescriptor("h-g-i-g-o")
    fmt.Printf("How: %s\n", desc) // Output: How: gps
}

Relation Values

Relation values specify the relationship type in link elements:

// Add a validated link with parent-point relation
err := event.AddValidatedLink("HQ-1", "a-f-G-U-C", "p-p")
if err != nil {
    if errors.Is(err, cotlib.ErrInvalidRelation) {
        log.Fatal(err)
    }
}

// Or add manually (validation happens during event.Validate())
event.AddLink(&cotlib.Link{
    Uid:      "CHILD-1",
    Type:     "a-f-G",
    Relation: "p-c", // parent-child
})

// Validate relation value
if err := cotlib.ValidateRelation("p-c"); err != nil {
    if errors.Is(err, cotlib.ErrInvalidRelation) {
        log.Fatal(err)
    }
}

// Get relation description
desc, _ := cotlib.GetRelationDescription("p-p")
fmt.Printf("Relation: %s\n", desc) // Output: Relation: parent-point

Available Values

How values include:

• h-e (manual entry)
• h-g-i-g-o (GPS)
• m-g (GPS - MITRE)
• And many others from both MITRE and TAK specifications

Relation values include:

• c (connected)
• p-p (parent-point)
• p-c (parent-child)
• p (parent - MITRE)
• And many others from both MITRE and TAK specifications

Validation

Event validation automatically checks how and relation values:

event.How = "invalid-how"
err := event.Validate() // Will fail

event.AddLink(&cotlib.Link{
    Uid:      "test",
    Type:     "a-f-G", 
    Relation: "invalid-relation",
})
err = event.Validate() // Will fail

Custom Types

You can register custom type codes that extend the standard prefixes:

// Register a custom type
cotlib.RegisterCoTType("a-f-G-E-V-custom")

// Validate the custom type
if err := cotlib.ValidateType("a-f-G-E-V-custom"); err != nil {
    log.Fatal(err)
}

ctx := cotlib.WithLogger(context.Background(), logger)

// Register types from a file
if err := cotlib.RegisterCoTTypesFromFile(ctx, "my-types.xml"); err != nil {
    log.Fatal(err)
}

// Register types from a string
xmlContent := `<types>
    <cot cot="a-f-G-custom"/>
    <cot cot="a-h-A-custom"/>
</types>`
if err := cotlib.RegisterCoTTypesFromXMLContent(ctx, xmlContent); err != nil {
    log.Fatal(err)
}

Generating Type Metadata (cotgen)

The cmd/cotgen utility expands the CoT XML definitions and writes the cottypes/generated_types.go file used by the library. Ensure the cot-types directory (or cottypes as a fallback) is present, then run:

go run ./cmd/cotgen
# or simply
go generate ./cottypes

Add your custom type entries to cottypes/CoTtypes.xml (or cot-types/CoTtypes.xml) before running the generator to embed them into the resulting Go code.

The test suite ensures generated_types.go is up to date. If it fails, regenerate the file with go generate ./cottypes and commit the result.

TAK Types and Extensions

The library supports both canonical MITRE CoT types and TAK-specific extensions. TAK types are maintained separately to ensure clear namespace separation and avoid conflicts with official MITRE specifications.

Adding New CoT Types

For MITRE/canonical types: Add entries to cottypes/CoTtypes.xml For TAK-specific types: Add entries to cottypes/TAKtypes.xml

The generator automatically discovers and processes all *.xml files in the cot-types/ directory (falling back to cottypes/ if needed).

TAK Namespace

All TAK-specific types use the TAK/ namespace prefix in their full attribute to distinguish them from MITRE types:

<!-- TAK-specific types in cottypes/TAKtypes.xml -->
<cot cot="b-t-f" full="TAK/Bits/File" desc="File Transfer" />
<cot cot="u-d-f" full="TAK/Drawing/FreeForm" desc="Free Form Drawing" />
<cot cot="t-x-c" full="TAK/Chat/Message" desc="Chat Message" />

Working with TAK Types

// Check if a type is TAK-specific
typ, err := cottypes.GetCatalog().GetType("b-t-f")
if err != nil {
    log.Fatal(err)
}

if cottypes.IsTAK(typ) {
    fmt.Printf("%s is a TAK type: %s\n", typ.Name, typ.FullName)
    // Output: b-t-f is a TAK type: TAK/Bits/File
}

// Search for TAK types specifically
takTypes := cottypes.GetCatalog().FindByFullName("TAK/")
fmt.Printf("Found %d TAK types\n", len(takTypes))

// Validate TAK types
if err := cotlib.ValidateType("b-t-f"); err != nil {
    log.Fatal(err) // TAK types are fully validated
}

Generator Workflow

1. The generator scans cot-types/*.xml (or cottypes/*.xml) for type definitions
2. Parses each XML file into the standard <types><cot> structure
3. Validates TAK namespace integrity (no a- prefixes with TAK/ full names)
4. Expands MITRE wildcards (a-.-) but leaves TAK types unchanged
5. Generates cottypes/generated_types.go with all types

Adding New Types

To add new CoT types to the catalog:

1. For MITRE types: Edit cottypes/CoTtypes.xml (or cot-types/CoTtypes.xml)
2. For TAK extensions: Edit cottypes/TAKtypes.xml (or cot-types/TAKtypes.xml)
3. For new categories: Create a new XML file in cottypes/ or cot-types/
4. Run go generate ./cottypes to regenerate the catalog
5. Verify with tests: go test ./cottypes -v -run TestTAK

Example TAK type entry:

<cot cot="b-m-p-c-z" full="TAK/Map/Zone" desc="Map Zone" />

Important: TAK types should never use the a- prefix (reserved for MITRE affiliation-based types) and must always use the TAK/ namespace prefix.

Event Predicates

The library provides convenient type classification with the Is() method:

// Create a friendly ground unit event
event, _ := cotlib.NewEvent("test123", "a-f-G", 30.0, -85.0, 0.0)

// Check various predicates
fmt.Printf("Is friendly: %v\n", event.Is("friend"))  // true
fmt.Printf("Is hostile: %v\n", event.Is("hostile")) // false
fmt.Printf("Is ground: %v\n", event.Is("ground"))   // true
fmt.Printf("Is air: %v\n", event.Is("air"))         // false

Thread Safety

All operations in the library are thread-safe. The type catalog uses internal synchronization to ensure safe concurrent access.

Security Features

The library implements several security measures:

• XML parsing restrictions to prevent XXE attacks
• Input validation on all fields
• Coordinate range enforcement
• Time field validation to prevent time-based attacks
• Maximum value length controls
• Configurable parser limits
• UID values are limited to 64 characters and may not contain whitespace
• Secure logging practices

// Set maximum allowed length for XML attribute values
// This protects against memory exhaustion attacks
cotlib.SetMaxValueLen(500 * 1024) // 500KB limit
cotlib.SetMaxXMLSize(2 << 20)    // 2MB overall XML size
cotlib.SetMaxElementDepth(32)    // nesting depth limit
cotlib.SetMaxElementCount(10000) // total element limit
cotlib.SetMaxTokenLen(1024)      // single token size

Logging

The library uses slog for structured logging:

• Debug level for detailed operations
• Info level for normal events
• Warn level for recoverable issues
• Error level for critical problems

logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
    Level: slog.LevelDebug,
}))

ctx := cotlib.WithLogger(context.Background(), logger)
log := cotlib.LoggerFromContext(ctx)
log.Info("logger ready")

Event Pooling

UnmarshalXMLEvent reuses Event objects from an internal pool to reduce allocations. When you are done with an event, return it to the pool:

evt, _ := cotlib.UnmarshalXMLEvent(context.Background(), data)
defer cotlib.ReleaseEvent(evt)

Build Tags

The optional novalidator build tag disables XML schema validation. When this tag is provided, ValidateAgainstSchema becomes a no-op and always returns nil, so any XML is parsed without verification, including malformed or malicious content.

Only use this tag when performance is critical and the input XML is already trusted. Do not use it when processing untrusted or potentially invalid CoT, as skipping schema validation may expose your application to malformed data.

go build -tags novalidator

Benchmarks

Run benchmarks with the standard Go tooling:

go test -bench=. ./...

This executes any Benchmark... functions across the module, allowing you to profile serialization, validation, or other operations.

Performance

This library is optimized for high-performance CoT processing with minimal memory allocations:

Core Operations (Apple M4)

Operation	Speed	Allocations	Memory	Throughput
Event Creation	157.4 ns/op	1 alloc	288 B	~6.4M events/sec
XML Generation	583.2 ns/op	4 allocs	360 B	~1.7M events/sec
XML Parsing	5.08 μs/op	73 allocs	3.48 KB	~197K events/sec
XML Decode w/ Limits	2.31 μs/op	49 allocs	2.62 KB	~433K events/sec

Type Validation

Type Pattern	Speed	Allocations	Throughput
Simple Types (a-f-G)	21.9 ns/op	0 allocs	~45.7M validations/sec
Complex Types (a-f-G-E-X-N)	22.3 ns/op	0 allocs	~44.8M validations/sec
Wildcards (a-f-G-*)	53.7 ns/op	0 allocs	~18.6M validations/sec
Atomic Wildcards (a-.-X)	32.3 ns/op	0 allocs	~31.0M validations/sec

Catalog Operations

Operation	Speed	Allocations	Throughput
Type Lookup	18.9 ns/op	0 allocs	~52.9M lookups/sec
Search by Description	67.4 μs/op	0 allocs	~14.8K searches/sec
Search by Full Name	104.4 μs/op	0 allocs	~9.6K searches/sec

XML Schema Validation

Metric	Performance	Allocations	Throughput Range
Average	2.89 μs/op	0 allocs	~346K validations/sec
Fastest	2.25 μs/op	0 allocs	~444K validations/sec
Slowest	5.25 μs/op	0 allocs	~190K validations/sec

Validation performance across 13 schema types (Contact, Track, Color, Environment, Precision Location, Shape, Event Point, Status, Video, Mission, TAK Version, Bullseye, Route Info)

Key Performance Features

• Zero-allocation lookups: Type catalog operations don't allocate memory
• Object pooling: XML parsing reuses event objects to minimize GC pressure
• Optimized validation: Fast-path validation for common type patterns
• Efficient searching: Pre-computed uppercase strings for case-insensitive search
• Minimal serialization overhead: Direct byte buffer manipulation for XML generation

Real-World Scenarios

High-frequency tracking: Process 200,000+ position updates per second Bulk operations: Validate millions of type codes with zero GC impact
Memory-constrained environments: Minimal allocation footprint Low-latency systems: Sub-microsecond event processing

Benchmarks run on Apple M4 with Go 1.21. Your mileage may vary by platform.

Documentation

For detailed documentation and examples, see:

• GoDoc
• CoT Specification

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Project History

Originally created by @pdfinn. All core functionality and initial versions developed prior to organisational transfer.