# Overview - Challenges

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If you have identified any challenges not listed here, please let us know by making a pull request in our GitHub Repository or contact us directly.
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## Data Collection

* Where to find OJA data? [#data-sources-and-oja-landscaping](https://www.oja-guide.de/steps/data-collection#data-sources-and-oja-landscaping "mention")
* How to collect OJA data? [#web-scraping](https://www.oja-guide.de/steps/data-collection#web-scraping "mention")
* How to store OJA data? [#job-posting-data-schema](https://www.oja-guide.de/steps/data-collection#job-posting-data-schema "mention")

## Data Enrichment

* How to segment a job ad? [#text-segmentation](https://www.oja-guide.de/steps/data-enrichment#text-segmentation "mention")
* How to identify duplicates? [#identifying-duplicates](https://www.oja-guide.de/steps/data-enrichment#identifying-duplicates "mention")
* How to extract occupations? [#normalising-job-titles](https://www.oja-guide.de/steps/data-enrichment#normalising-job-titles "mention")
* How to extract skills and competences? [#extracting-skills](https://www.oja-guide.de/steps/data-enrichment#extracting-skills "mention")

## Evaluation and Quality Control

* How to evaluate extraction and classification algorithms? [#evaluation-metrics](https://www.oja-guide.de/steps/evaluation-and-quality-control#evaluation-metrics "mention")
* How to create a gold standard for evaluation? [#gold-standard-annotation-and-quality](https://www.oja-guide.de/steps/evaluation-and-quality-control#gold-standard-annotation-and-quality "mention")

## Taxonomies and Ontologies

* Which taxonomies are there (ISCO, ESCO, KLDB, etc.)? [#taxonomies-for-online-job-ad-analysis](https://www.oja-guide.de/steps/taxonomies-and-ontologies#taxonomies-for-online-job-ad-analysis "mention")
* How to develop a taxonomy? [#developing-a-taxonomy](https://www.oja-guide.de/steps/taxonomies-and-ontologies#developing-a-taxonomy "mention")
* How to evaluate a taxonomy? [#data-standards-for-taxonomies-and-ontologies](https://www.oja-guide.de/steps/taxonomies-and-ontologies#data-standards-for-taxonomies-and-ontologies "mention")

## Dataset Curation and Representativity Analysis

* How to deal with duplicates? [#deduplication](https://www.oja-guide.de/steps/dataset-curation-and-representativity-analysis#deduplication "mention")
* How to validate an OJA dataset/sample? [#representativity-analysis](https://www.oja-guide.de/steps/dataset-curation-and-representativity-analysis#representativity-analysis "mention")
* What to report?  [#reporting-results](https://www.oja-guide.de/steps/evaluation-and-quality-control#reporting-results "mention")